SOME REACTIONS
Of
PHOSPHORUS YLIDS
By
BRIAN JOHN Y/ALKER
A T h e s i s s u b m i t te d f o r th e d e g re e o f D o c to r o f P h i lo s o p h y
o f th e
U n i v e r s i t y o f L e i c e s t e r
1966
UMI Number: U 296388
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STATEMENT
The work d e s c r i b e d i n t h i s t h e s i s was c a r r i e d o u t by th e
a u th o r i n th e D epartm en t o f C h e m is try o f t h e U n i v e r s i t y
o f L e i c e s t e r u n d e r th e s u p e r v i s i o n o f D r. S . T r i p p e t t .
No p a r t o f i t i s c o n c u r r e n t l y b e in g s u b m i t t e d ’f o r any
o th e r d e g re e .
O c to b e r 19^3 — May 1966
S ig n e d
(B . J . V /alker)
ACKNO\YLEDGEMENTS
The a u th o r would l i k e to r e c o r d h i s s i n c e r e th a n k s to
D r. S . T r i p p e t t f o r h i s s u p e r v i s i o n an d c o n s t a n t
e n c o u ra g e m e n t , t o t h e S c ie n c e R e s e a rc h C o u n c i l f o r th e
aw ard o f a R e se a rc h S t u d e n t s h ip and to M iss R. E. O’N e i l l
f o r th e ty p in g in v o lv e d .
CONTENTS
Summary
I n t r o d u c t i o n 1
P h o sp h o ran e s and P h o sp h o ru s Y l i d s 1
The p r e p a r a t i o n o f P h o sp h o ru s Y l id s k
R e a c t io n s o f P h o sp h o ru s Y l id s 19
( a ) P h o sp h o ru s Y l id s i n th e W i t t i g R e a c t io n 19
(h ) O th e r R e a c t io n s o f P h o sp h o ru s Y l id s
p ro c e e d in g v i a I n t e r m e d i a t e B e ta in e s 22
( c ) R e a c t io n s o f P h o sp h o ru s Y l i d s n o t
p ro c e e d in g v i a I n t e r m e d i a t e B e ta in e s 1+3
The R e a c t io n s o f P h o sp h o ra n e s w i th A c t i v a t e d T r i p l e
Bonds 53
E x p e r im e n ta l 71
Some R e a c t io n s o f P h o sp h o ru s C o n ta in in g B e ta in e s
i n W i t t i g R e a c t io n s 83
The Mechanism o f th e W i t t i g R e a c t i o n 83
R e a c t io n s o f I n t e r m e d i a t e B e t a in e s i n th e W i t t i g
R e a c t io n o t h e r t h a n O l e f i n F o rm a t io n 87
Abnormal R e a c t i o n s o f t h e B e ta in e s
RgP-C H s ~C H (5)R 98
E x p e r im e n ta l 106
A bnorm al Q u a r t e r n i s a t i o n R e a c t io n s o f Some
A c t i v a t e d A lk y l H a l id e s 1 2 0 (a )
( a ) R e a c t io n s P r o c e e d in g v i a E no l-P hosphon ium
S a l t s 120 (a )
(b ) The Mechanism o f E no l-P hosphon ium S a l t
f o r m a t io n 127
( c ) The R e a c t io n o f T r ip h e n y lp h o s p h in e w i th
1 - B r o m o - l - N i t r o a lk a n e s 128
E x p e r im e n ta l 139
The R e a c t i o n o f A ld eh y d es and K e ton es w i th
T r i v a l e n t P h o sp h o ru s Compounds 1 4 3 (a )
E x p e r im e n ta l 154-
R e f e r e n c e s 157
SmiMARY
Both th e m ethods o f p r e p a r a t i o n , and th e r e a c t i o n s ,
o f p h o sp h o ru s y l i d s a r e re v ie w e d .
The r e a c t i o n s o f a c t i v a t e d t r i p l e bonds w i th
p h o sp h o ru s y l i d s a r e s t u d i e d and shown to g iv e r e a r r a n g e d
p r o d u c t s , p r o b a b ly v i a a fo u r-m em b ered c y c l i c t r a n s i t i o n
s t a t e .
A b r i e f o u t l i n e o f th e m echanism o f th e W i t t i g
r e a c t i o n i s g iv e n , and r e a c t i o n s o f i n t e r m e d i a t e b e t a i n e s i n
th e W i t t i g r e a c t i o n , o t h e r th a n o l e f i n f o r m a t io n , a r e s t u d i e d .
The r e a c t i o n o f p h o s p h in e s w i th e p o x id e s i s u se d to d e m o n s t r a te
b e t a i n e d i s s o c i a t i o n and r e a r r a n g e m e n t .
F o l lo w in g a re v ie w o f ab n o rm a l q u a t e r n i s a t i o n
r e a c t i o n s o f a c t i v a t e d a l k y l h a l i d e s , th e r e a c t i o n o f t r i p h e n y l
p h o sp h in e w i th 1- b r o m o - n i t r o a l k a n e s , t o g iv e a -h y d ro x y im in o -
a l k y l phosphonium s a l t s , i s d i s c u s s e d .
A b r i e f rev ie w o f th e r e a c t i o n s o f a ld e h y d e s and
k e to n e s w i th t r i v a l e n t p h o sp h o ru s compounds i s f o l lo w e d by a
more d e t a i l e d s tu d y o f th e r e a c t i o n o f a m in o p h o sp h in es w i th
a ld e h y d e s and k e to n e s to g iv e r e a r r a n g e d p r o d u c t s .
- 1 -
INTRODUCTION
P h o sp h o ra n e s and P h o sp h o ru s Y l i d s .
P h o s p h o ru s , u n l i k e n i t r o g e n , i s a b l e to e x i s t
i n th e q u in q u e v a le n t s t a t e b e c a u s e i t h a s r e a d i l y a v a i l a b l e
d o r b i t a l s i n t o w hich i t s o u t e r s h e l l c an e x p an d . The term
ph o sp h o ran e i n c o r p o r a t e s any compound c o n t a i n i n g f i v e v a l e n t
p h o sp h o ru s .
W ith in th e g e n e r a l g ro up o f compounds known a s
p h o sp h o ra n e s t h e r e a r e two d i s t i n c t t y p e s . The f i r s t
c o n t a i n q u in q u e v a le n t p h o sp h o ru s bonded c o v a l e n t l y t o f i v e
s e p a r a t e g r o u p s , w h i le th e se c o n d have f o u r c o v a l e n t bonds
and a f i f t h , c h a rg e s e p a r a t e d , bond .
The p a r e n t compound o f t h e f i r s t ty p e c a n be
c o n s i d e r e d to be p h o sp h o ru s p e n ta h y d r id e (P H ^). B o th th e1 ,2
t h e o r e t i c a l p o s s i b i l i t y , and th e a c t u a l e x i s t e n c e o f t h i s
compound have b e e n s t u d i e d . The e v id e n c e p o i n t s t o th e f a c t
t h a t i t h a s no f i n i t e e x i s t e n c e even a t t e m p e r a tu r e s a s low
a s —100®C. I t i s s u g g e s te d t h a t i n th e f r e e p h o sp h o ru s
atom th e 3 d o r b i t a l s a r e to o d i f f u s e f o r good b on d ing w i th
h y d ro g en .
The se co n d ty p e o f p h o sp h o ra n e s a r e known a s y l i d s
-2 -
and have a s t r u c t u r e b e s t r e p r e s e n t e d a s a r e s o n a n c e h y b r i d
o f t h e c o v a l e n t and i o n i c fo rm s ( l a ) and ( l b )
RqP = X < --------> R g P -X
( l a ) ( l b )
X c a n be c a r b o n - th e a l k y l i d e n e p h o s p h o ra n e s ( 2 ) , o r
n i t r o g e n - t h e im in o p h o sp h o ra n e s ( 3 )#
R3.P = CRg R3 P = NR
(2 ) (3)
B oth th e s e g ro u p s o f compounds ov/e t h e i r r e a c t i v i t y to th e
a n i o n i c c h a r a c t e r o f t h e i r X atom and were o r i g i n a l l y* ,5
p r e p a r e d by S t a u d i n g e r i n 1919.
Some y l i d s do n o t e x i s t a s shown i n ( l a ) and ( l b ) ,
T hese a r e p h o sp h o ru s y l i d s h a v in g a p - c a r b o n y l g ro up ( 4 ) ,
w hich g i v e s a f u r t h e r p o s s i b i l i t y f o r r e s o n a n c e s t r u c t u r e s .
R3 P = CR — C — R 0
(4 )
A l th o u g h i n many o f t h e i r r e a c t i o n s y l i d s o f t h i s
ty p e behave a s i f t h e y a r e i n th e form (4 ) , t h e r e i s
c o n s i d e r a b l e e v id e n c e to show t h a t th e y a r e i n f a c t b e s t
- 3 -
r e p r e s e n t e d by t h e re s o n a n c e h y b r i d o f fo rm s ( 4 ) and ( 3 ) .
RqP = G E - C - R <---------- > R o P -C E = C - R& L
(W C5)
6A skn es h a s shown t h a t i n compounds o f t h i s ty p e th e
c a r b o n y l s t r e t c h i n g f r e q u e n c y f a l l s t o th e 1 ,6 0 0 cm~^ r e g i o n ,
w hich s u g g e s t s a c o n s i d e r a b l e c o n t r i b u t i o n from th e form
(3 ) » The o r i g i n a l s u g g e s t i o n o f th e p h o s p h o b e ta in e form7
(5 ) was b a se d on d i p o l e moment m e a su re m e n ts . The a c e ty l e n e8 . .
s y n t h e s i s o f T r i p p e t t i s b a s e d on th e a s s u m p t io n t h a t (5 )
h a s a c o n s i d e r a b le c o n t r i b u t i o n .
The P r e p a r a t i o n o f P h o sp h o ru s Y l i d s .
*The f i r s t p r e p a r a t i o n o f a p h o sp h o ru s y l i d
i n v o lv e d t r e a t i n g t r ip h e n y lp h o s p h i n e w i th a d i a z o - a l k a n e
and h e a t i n g th e p h o s p h in e a z in e ( 6 ) fo rm ed .
Pha P + NoCR=^R2 _► P haP = K - N = CR^R213;J
iPh3..P=CE^R® + Ha
9B estm ann h a s a l s o p r e p a r e d p h o s p h in e a z in e s by th e a c t i o n o f
d ib r o m o t r ip h e n y lp h o s p h o r a n e ( 7 ) on h y d ra z o n e s i n th e p r e s e n c e
o f a b a s e such a s t r i e t h y l a m i n e .
PhafBrg + H H 8-H = CEs: PhaP = N - N = CR3
(7)
I t i s s u g g e s te d t h a t p h o sp h o ra n e s a r e fo rm ed from
p h o s p h in e a z in e s v i a t r ip h e n y lp h o s p h in e and th e c a rb e n e :GR^R®,
w hich combine t o g iv e th e p h o sp h o ra n e . D i r e c t r e a c t i o n be tw een
t r ip h e n y lp h o s p h in e and c a r b e n e s h a s b e en r e p o r t e d ,10 ,1 1
C h lo ro m e th y le n e w i th t r ip h e n y lp h o s p h in e a t -30®C gave a 63^10 ,11
y i e l d o f c h lo r o m e th y le n e t r ip h e n y lp h o s p h o r a n e ( 8 ) , w hich
c o u ld be r e a c t e d w i t h a ld e h y d e s a n d k e to n e s i n a W i t t i g
r e a c t i o n to g iv e v i n y l c h l o r i d e s .
-5 -
C3îa:Cls + LlC^Ha -» :GB3 1 P % P = CECI
( 8 )
a ld e h y d e s o r k e to n e s
R^E®C= CHCl + Pha PO
11 ,1 2 l aD ic h lo ro m e th y le n e and m e th y le n e a l s o r e a c t w i th
t r ip h e n y lp h o s p h i n e to g iv e t h e c o r r e s p o n d in g y l i d s .
D ic h lo r o m e th y le n e t r ip h e n y lp h o s p h o r a n e (9 ) h a s
a l s o b e e n p r e p a r e d by th e r e a c t i o n o f t r i p h e n y lp h o s p h i n e / 14w i th c a r b o i y c e t r a c h l o r i d e . T h is r e a c t i o n a p p e a r s t o p r o c e e d
w i th a t t a c k o f p h o sp h in e on h a lo g e n to g iv e th e phosphonium
s a l t ( l O ) , e l i m i n a t i o n o f c h l o r i d e l e a d s t o d i c h l o r o t r i p h e n y l -
p h o sp h o ra n e and d i c h lo r o c a r b e n e w hich can r e a c t w i th more
p h o sp h in e to g iv e d i c h lo r o m e th y le n e t r ip h e n y lp h o s p h o r a n e ( 9 ) .
P h g f : + C l - C C l a P h ^ P - C l CCI3"
( 1 0 )PhaPC la + tCCl-B > PhaP = CClg
C9)
The r e a c t i o n o f c a rb o iy te t ra b ro m id e w i th t r i p h e n y lp h o s p h i n e i s 16 /
s i m i l a r . However i f t h e p r o d u c t i s t r e a t e d w i th h y d ro g e n
b rom ide t o g iv e th e phosphonium s a l t ( l l ) , t h i s w i l l u n d e rg o
r e a c t i o n w i th t r i p h e n y lp h o s p h i n e t o g iv e b ro m o m e th y le n e -
t r ip h e n y lp h o s p h o r a n e (’12 ) .
- 6 -
P h g f = CBra PhaP-C H B ra Bi>“
( 11)
PhaPf
PhgjP = CHBr + Phg PBPg
( 12)
P h o sp h o ru s y l i d s c a n a l s o be p r e p a r e d from d ih a lo p h o s p h o r a n e s16
o f th e ty p e EgPGlg. H o rn e r an d O e d ig e r h av e shovm t h a t i n
th e p r e s e n c e o f t e r t i a r y am ines d ih a lo p h o s p h o r a n e s w i l l r e a c t
w i th a c t i v e m e th y le n e g ro u p s t o g iv e p h o sp h o ra n e s ( 1 3 ) .
EaPClg + CHb RaP = C (1 3 )\ y
V/here X and Y a r e e l e c t r o n w i th d ra w in g g ro u p s .
A f u r t h e r i n d i r e c t m ethod o f p r e p a r i n g p h o sp h o ra n e s
h a s b e e n d e v e lo p e d by B estm ann. I n a s e r i e s o f17 ,18 ,19 ,20 ,21 ,22 ,23
p a p e r s he h a s shown t h a t a l k y l a t i o n and
a c y l a t i o n o f p h o sp h o ra n e s l e a d s t o c x - s u b s t i t u t e d p r o d u c t s .
T re a tm e n t o f a l k y l i d e n e p h o sp h o ra n e s (1 4 ) w i th a l k y l h a l i d e s
l e a d s t o a - s u b s t i t u t e d phosphonium s a l t s ( 15 ) .
PhaP= CHE + Ri^I -» PhaP-CHEiR^ l “
(1 4 ) (1 5 )
T h is i s a l s o t r u e f o r a c y l a t i o n . H ow ever, i f t h e a -h y d ro g e n
-7 -
i n th e phosphonium s a l t ( 1 5 ) i s more a c i d i c t h a n t h a t
i n th e phosphonium s a l t , o b t a i n e d on t r e a t i n g t h e p h o sp h o ra n e
(li+) w i th a c i d , t h e r e a c t i o n d o es n o t s to p a t t h i s p o i n t .
The phosphonium, s a l t (1 5 ) i s d e h y d ro h a lo g e n a te d by th e
p h o sp h o ran e ( l 4 ) t o g iv e ( l 6 ) and ( 1 7 ) .
PhaP-G H E^R I" + P h g P = CRR PhaP=CER^ + P h aP -C H gR I ~
(15 ) (1 4 ) ( 16 ) ( 1 7 )
T h is r e a c t i o n i s known a s t r a n s y l i d a t i o n and t a k e s
p l a c e when i s an e l e c t r o n w ith d ra w in g g ro u p . I n c a s e s o f
t h i s ty p e o n ly a 50^ e q u i v a l e n t o f R^I i s added i n o r d e r t o
a v o id th e c o m p l i c a t io n s o f a d d i t i o n to ( l 6 ) .
P h o sp h o ra n e s w i th a l a r g e ra n g e o f a - s u b s t i t u e n t s17 ,1 $ so
c a n be p ro d u c e d by t h i s m ethod , e . g . —COR,84 85 38 2 3
-CH O , - B r , - T , -COOR.
P h o sp h o ra n e s may a l s o be p r e p a r e d f r o n u n s a t u r a t e d2 7/ 28
compounds. Oda and Hoffm ann have shown t h a t p h o s p h in e s
w i l l add to a c t i v a t e d d o u b le b o n d s , i n e t h a n o l , p re su m a b ly
i n i t i a l l y fo rm in g th e b e t a i n e ( 1 8 ) which th e n t a k e s u p , and
l o s e s , a p r o t o n f ro m , and t o , th e s o l v e n t to g iv e t h e more
s t a b l e p h o sp h o ra n e ( 19 ) .
—8—
+ —»Rq;P + CHa = CHX —> R s P - C H a - G E - X
(18) Eton
E g P s CH— C%X + EtOE <---- R a P -C H g ,-C H a -X EtO
(1 9 )
Where X can be — CE> — COOEt, — GOEHg .
Hoffmann c a r r i e d o u t t h e s e r e a c t i o n s i n th e p r e s e n c e o f
a c i d and i s o l a t e d th e c o r r e s p o n d in g phosphonium s a l t s ,
w h i le Oda add ed a ld e h y d e s and i s o l a t e d th e o l e f i n s p ro d u c e d
from a W i t t i g e l i m i n a t i o n ( s e e p . 83 )•8 9 3 0
O such, and o t h e r w o r k e r s , have ad d ed
t r ip h e n y lp h o s p h in e t o m a le ic a n h y d r id e t o g iv e t h e phospho
b e t a i n e ( 2 l ) . T h is r e a c t i o n p re su m a b ly t a k e s p l a c e by a
m echanism s i m i l a r t o t h a t d e s c r i b e d a b o v e , i n i t i a l f o r m a t io n
o f t h e b e t a i n e ( 2 0 ) and p r o t o n t r a n s f e r to g iv e th e
p h o s p h o b e ta in e .
PhaP
PbgP
( 20 ) ( 21 )The r e a c t i o n o f me th y le n e t r i p h e n y l p h o s p h o r a n e w i t h
t e t r a m e t h y lc y c l o b u t a d i o n e l e a d s t o th e p h o s p h o b e ta in e ( 22 ) ,
-9 -
p e r h a p a by i n i t i a l a t t a c k a t a c a r b o n y l g rou p f o l lo w e d by
r i n g open in g and a p r o t o n t r a n s f e r .Me
Me
Me"Me
Phr Me
. ? SP i% T -G E = C C ^ M e <-
C GH/ \ \
Me Me Me
( 22)
OT Me
P —f GH C — C —
^ 4 'M e yMe
Me* i ^ M e
P h a ,? CH— C
Me I
32S e y f e r t h h a s added d ip h e n y lm e th y lp h o s p h in e t o
benzyne t o p ro d u c e m e th y le n e t r ip h e n y lp h o s p h o r a n e ( 2 3 ) , w hich
was t r a p p e d w i th c y c lo h ex a n o n e i n a c o n v e n t io n a l W i t t i g
r e a c t i o n .
P h g P -C H a +
+ Pha,PO « Pha.P = CHa
-1 0 -
A l l t h e s e m e thod s may be u s e d t o p ro d u ce
p h o s p h o r a n e s , how ever t h e m ost g e n e r a l m ethod o f p r e p a r a t i o n
i s the t r e a tm e n t o f t h e c o r r e s p o n d in g phosphonium s a l t w i th
a s u i t a b l e b a s e .
+■ —Ea,P-CHR^R® + B ^ R aP sC R ^E ® + BH
33A w ide ra n g e o f b a s e s a r e a v a i l a b l e and th e
c h o ic e d ep en d s on th e ty p e o f p h o sp h o ra n e t o be p r e p a r e d , i t s
s t a b i l i t y t o f u r t h e r r e a c t i o n w i th t h e m ed ia and th e e a s e o f
rem o v a l o f th e a —p r o t o n i n th e phosphonium s a l t .
G e n e r a l l y p h o sp h o ra n e s c a n be d i v i d e d i n t o two
g r o u p s , " s t a b l e * * and * * u n s tab le **. The ** s t a b l e ** p h o sp h o r
a n e s a r e th o s e i n which th e n e g a t i v e c h a rg e r e s i d i n g on th e
a —c a rb o n atom i s d e l o c a l i s e d to some e x t e n t by s u b s t i t u e n t s .
When t h i s d e l o c a l i s a t i o n i s n o t p r e s e n t we h av e th e **u n s t a b l e **
p h o s p h o ra n e s . The e l œ t r o n w i th d ra w a l by s u b s t i t u e n t s which
s t a b l i s e s t h e p h o sp h o ra n e w i l l a l s o a i d rem o v a l o f a p r o t o n
from th e phosphonium s a l t , th u s th e p r o d u c t i o n o f **u n s t a b l e **
p h o sp h o ra n e s r e q u i r e s a more p o w e r f u l b a se t h a n t h a t o f
**8 t a b l e ** p h o s p h o ra n e s .
B a se s u s e d t o p ro d u c e * * u n s tab le ** p h o sp h o ra n e s a r e
u s u a l l y m e t a l a l k y l s , commonly l i t h i u m a l k y l s . The m echanism
o f p h o sp h o ra n e f o r m a t io n u s in g t h e s e b a s e s h a s y e t t o be f u l l y
-1 1 -
e x p l a i n e d , an d a number o f s i d e r e a c t i o n s h a v e b e e n shown
t o t a k e p l a c e . I n th e r e a c t i o n o f m e th y l t r ip h e n y lp h o s p h o n iu m3 4r ,3 6
brom ide w i th n - b u t y l - l i t h i u m , S e y f e r t h h a s shown
t h a t , a s w e l l a s b u t a n e , a 2.0fo y i e l d o f b e n ze n e i s p ro d u c e d
and t r e a t m e n t o f te t r a p h e n y lp h o s p h o n iu m b rom id e w i th
m ethy1- l i t h i u m g i v e s a t l e a s t ^8^ o f m e t h y l e n e t r i p h e n y l -3 4 , 3 6
p h o sp h o ra n e . H ow ever, i f the b a se i s chan g ed to
v in y 1- l i t h i u m th e p r o d u c t s from t h i s r e a c t i o n a r e s t y r e n e and36
t r i p h e n y lp h o s p h i n e . S e y f e r t h h a s p ro p o s e d th e q u in q u e -
v a l e n t p h o sp h o ru s d e r i v a t i v e i 2 k ) a s th e i n t e r m e d i a t e i n
th e s e r e a c t i o n s .
Ph Ph I Ph
+ - \ I /P h tP Br + CEiaLi ^ ^P Ph@P = GH&
/ ^ P h
C 2 k )
The r e a c t i o n o f l i t h i u m - a l k y l s w i th h a l o m e t h y l t r i p h e n y l -37
phosphonium s a l t s i s a l s o com plex . A l th o u g h c h lo r o r a e th y l -
t r ip h e n y lp h o s p h o n iu m b rom id e gave o n ly c h lo r o m e t h y l e n e t r i p h e n y l
p h o sp h o ra n e and b e n ze n e on t r e a t m e n t w i th l i t h iu m - p h e n y 1 ,
b ro m o m e th y l t r ip h e n y lp h o sp h o n iu m brom ide gave b e n ze n e ( 39^ ) and
-1 2 -
■bromobenzene u n d e r th e same c o n d i t i o n s , p re s u m a b ly by
a t t a c k a t b o th c a rb o n —h y d ro g en and c a rb o n -b ro m in e b o n d s .
Pha P— C H a - C l Br"
Phg P — GHg. — Br , Br
PhLi » PhaP = GHGl Hr PhH + L iB r
P haP = CHBr + PhH + L iB r
PhgP = GHg + PhBr L iB r
When th e r e a c t i o n i s e x te n d e d t o i o d o m e th y l t r i p h e n y lp h o s -
phonium i o d id e th e p r o p o r t i o n o f a t t a c k on th e h a lo g e n - c a r b o n
bond i s i n c r e a s e d s t i l l f u r t h e r , t h e p r o d u c t s b e i n g b enzene
( 2 % ) and io d o b en z en e ( 7 0 ^ ) . T h is t r e n d i s i n ag reem en t w i th
th e o b se rv e d r e a c t i v i t y o f c a rb o n h a lo g e n b onds to w a rd s38 39
l i t h i u m h y d r o c a rb o n s . K o b r ic h h a s fo u n d t h a t c a r b o n -
•h a lo g e n c le a v a g e i s m in im is e d by th e u se o f p i p e r i d y 1- l i t h i u m
a s th e b a s e . He o b ta in e d a 70^ y i e l d o f o l e f i n from th e
r e a c t i o n s o f p—iono ne w i th b ro m o m e th y le n e t r ip h e n y lp h o s p h o ra n e
p ro d u c e d i n t h i s way.
LiCaHgHPhaP — GHg: — Br Br PhaP= GHBr
—13-
I n a l l t h e s e r e a c t i o n s a n e x c e s s o f l i t h i u m
h y d ro c a rb o n m ust be a v o id e d b e c a u se th e a n io n ( 2 5 ) may be40
p r o d u c e d , which c a n u n d e rg o r e a r r a n g e m e n t t o g iv e t h e
b e n z y l id e n e p h o s p h o ra n e ( 2 6 ) .
/PhPh3 P = a i C l P h a P ^ C T ------------ >• PhgRP = OHPh
( 2 5 ) ( 2 6 )
To p ro d u c e ** u n s t a b l e ** p h o s p h o ra n e s , v e r y r e a c t i v e b a s e s
su ch a s th e l i t h i u m h y d ro c a r b o n s m ust be u se d , and i t i s j u s t
t h i s r e a c t i v i t y t h a t h i n d e r s t h e i r u s e i n th e p r o d u c t i o n o f
many p h o s p h o ra n e s . I f t h e phosphonium s a l t c o n t a in s a
g rou p w hich w i l l r e a c t w i th t h e l i t h i u m h y d ro c a rb o n ( e . g .
c a r b o n y l ) t h e n a l k a l i - m e t a l a l k o x i d e s c a n be u s e d . These
may be em ployed i n a v a r i e t y o f s o l v e n t s ( e . g . t h e p a r e n t
a l c o h o l , H ,N -d im e th y lfo rm a m id e , h e x a m e th y lp h o s p h o r ic
t r i a m i d e ) and on a d d i t i o n o f th e phosphonium s a l t an
e q u i l i b r i u m i s e s t a b l i s h e d : —
Ph. .f-CHR^R® + "OR si Ph«P=CR^R® + ROH
Some phosphonium a l k o x i d e s c a n decompose to p h o sp h in e
o x id e s ( s e e p . 3h) and so th e p h o sp h o ra n e i s b e s t u s e d
q u i c k l y .
-1 4 -
A n o th e r b a se w hich i s becom ing w id e ly u se d h a s
b e e n d e v e lo p e d by C o rey . Sodium h y d r id e d i s s o l v e s i n
d im e th y ls u lp h o x id e ( 2? ) to g iv e th e s u lp h o x id e a n io n (28 )
and h y d ro g e n .
CHa CHg\fN = 0 - S S Ë » ' ^ s - o + %
CI% CEo N a*
(27) . (28)
T h is a n io n i s a n e x t r e m e ly p o w e r fu l b a s e and th e sy s tem h a s
th e a d v a n ta g e t h a t d im e th y ls u lp h o x id e i s c o m p le te ly m i s c i b l e42
w i th w a te r . How ever, t h e a n io n w i l l r e a c t w i th k e to n e s
and t h i s can c a u se c o m p l i c a t i o n s .
Sodium h y d ro x id e a n d e v e n , i n e x c e p t i o n a l c a s e s ,
sodium b i c a r b o n a t e , c a n be u s e d a s a b a s e , b u t o n ly to p ro d u ce
th e more s t a b l e p h o s p h o ra n e s . E th o x y c a r b o n y lm e th y le n e t r i -/ \ * 3p h e n y lp h o s p h o ra n e ( 2 9 ) c a n be p ro d u c e d i n t h i s way, a t
0®G i n aqueous s o l u t i o n .
. Br~ HaOH.P h a f - CHa -COOEt ""o^C = CH-COOEt
Not a l l p h o sp h o ru s y l i d s may be p r e p a r e d by th e
—15-
t r e a tm e n t o f a phosphonium s a l t w i th th e a p p r o p r i a t e b a s e .
I f a lk y l t r ip h e n y lp h o s p h o n iu m s a l t s , h a v in g i n th e p - p o s i t i o n ,
i n th e a l k y l g ro up a g r o u p ,w hich i s c a p a b le o f s t a b l e e x i s t e n c e
a s an a n io n o r u n c h a rg e d m o le c u le , a r e t r e a t e d w i th b a se t h e y
may e l i m i n a t e t h i s g ro u p to g iv e a v in y l t r ip h e n y lp h o s p h o n iu m
s a l t .
Pha P - C H a - C H a P h a P C H g ,
+ iP h a ,P -C H = CHa X
+ 44 46 45T h is o c c u r s w here X i s : - P hgP , — OEt, h a lo g e n , and
46h y d r o x y l , and i s r e v e r s i b l e u n d e r th e c o r r e c t c o n d i t i o n s .
I t i s ev en p o s s i b l e f o r t h i s e f f e c t t o be t r a n s m i t t e d th ro u g h46
a c o n ju g a te d sy s te m .
P haP = C H - GH= C H - C% - PPhg ^ P h a P - CH= C M - CH= GHg + P h g?
X“ X”
47 2 1 ,4 8Mondon, and o t h e r w o r k e r s , have shown t h a t a s i m i l a r
r e a c t i o n t a k e s p l a c e w i th CO"" b ro m o b u ty l t r ip h e n y lp h o s p h o n iu m
b rom ide on t r e a tm e n t w i th p h e n y l - o r b u t y l - l i t h i u m . The
e x p e c te d p h o sp h o ra n e (3 0 ) b e in g p ro d u c e d i n i t i a l l y and th e n
u n d e rg o in g s e l f a l k y l a t i o n to g iv e e y e lo b u ty l t r ip h e n y lp h o s p h o n iu m
b ro m id e .
-1 6 -
Pha p - (CHj >4, - B r B r PhgP ÇH» - ^ r
( 3 0 ) CHg— GHg
IP h a P -C H -C H g Br
CHg-CHg46 ,49
V a r io u s w o rk e rs h av e shown t h a t v i n y l -
phosphonium s a l t s th e m se lv e s b ehave a b n o rm a lly i n th e p r e s e n c e
o f b a s e . Keough and G rayson t r e a t e d th e v iny Iphosphon iu rn
s a l t (.3 1 ) w i th a s e r i e s o f a n io n s and showed t h a t a d d i t i o n
o c c u r r e d a c r o s s th e d o u b le bond i n p r e f e r e n c e to th e rem oval
o f an a - p r o t o n .
+ - X“ +E3 P - C E = GHg Y ■■> R3 P - G H 2 - C H g - X Y
(31 )
46 ,49 46 ,49 46, 49X c o u ld be c a rb o n , n i t r o g e n , oxygen , s u lp h u r
46o r p h o s p h o ru s .
49S ch v /e ize r and L ig h t h av e a l s o shown t h a t inhen
XH i s th e s u b s t i t u t e d p y r r o l e ( 3 2 ) , th e i n i t i a l M ic h ae l a d d i t i o n
p r o d u c t u n d e rg o e s an i n t e r n a l W i t t i g r e a c t i o n to g iv e compound
( 3 3 ) i n h ig h y i e l d .
-1 7 -
n -
^ C H O
NaHEtgO a
Br~P h a P - c m = cais,
N ' CHOHa+
(32)
a H I0=0
I ^ +GHg - GH - PPhg
VL C m . . -
CHo - & - PPho
(33)
T h is ty p e o f r e a c t i o n h a s b e e n d e v e lo p e d i n t o a g e n e r a l r i n g5 0
s y n t h e s i s .
V/hen phosphonium s a l t s w i th a k e to g ro up i n th e
0 p o s i t i o n a r e t r e a t e d w i th sodium a lk o x i d e s th e p h o sp h o ra n e
i s i n i t i a l l y f o r m e d ,b u t th e n u n d e rg o e s an i n t e r n a l W i t t i g& ±.
r e a c t i o n to p ro d u c e a c y c l i c o l e f i n .
P1% P = C E - (CHa )3 - G O - P b P h aP O + P h - C H - ( C H a ) a
'^ C H
A s e r i e s o f t h e s e r e a c t i o n s have b e e n c a r r i e d o u t
-1 7 a -
on phosphonium s a l t s o f t h e ty p e (3U)
PhcP-C H a - (C H a ) j j - COPh B r“
L3k)
When n = l^ a n d sodium e th o x i d e i s u se d a s a b a s e , a p - e l i m i n a t l o n62
t a k e s p l a c e t o g iv e t r i p h e n y lp h o s p h i n e .
P h s , :^ GHg: CO - Ph -* Phg^P + CH3 = C E - COPh
OEt
H ow ever, i f l i t h i u m p h e n y l i s u s e d a s th e b a s e , 1 ,452
diphenyl-1,4 -c y c lo h e x a d ie n e i s fo rm e d , p re s u m a b ly by an
i n t e r m o l e c u l a r r e a c t i o n #
When n = 2 , no o l e f i n i s fo rm ed u n d e r a n y c o n d i t i o n s ,53
and o n ly i n s m a l l y i e l d when n = 4 .
phosphonium s a l t s w i th e s t e r g ro u p s i n th e ^ j S and £ p o s i t i o n s i n t h e s i d e c h a in g iv e a c y l a t e d p h o s p h o ra n e s
6 4when t r e a t e d w i th sodium a lk o x i d e s .
P h o P = C H - ( C % ) n - C ( -4 P h 3 P = C ^ ^ F ^ ) n^ O E t 3 0 - ^
0 ^n = 2 , 3 , 4 .
66Bestm ann h a s a l s o shown t h a t p y r o l y s i s o f th e
l a c t o n e ( 3 3 ) l e a d s t o d e c a r b o x y l a t i o n and th e f o r m a t io n o f
—18-“
th e c y c lo p ro p y lp h o sp h o n iu m s a l t (36)#
CHg — Œ — PPha; 180 -
B r 190®G^ COg + CHs — ,
GH<
GH PPhaBp-
(36)
-1 9 -
R e a c t i o n s o f P h o sp h o ru s Y l l d s #
( a ) P h o sp h o ru s Y l l d s i n th e W i t t i g R e a c t io n
The enorm ous i n t e r e s t i n t h e r e a c t i o n s o f
p h o sp h o ru s y l i d s , o v e r t h e p a s t d e c a d e ,s t e m s m a in ly from th e5 6
d e v e lo p m e n t , by W i t t i g , o f a g e n e r a l o l e f i n s y n t h e s i s
i n v o lv i n g th e s e compounds.
A l a r g e number o f r e v ie w s on th e W i t t i g r e a c t i o n33 ,46 ,6T ,68 ,69 ,6 0 ,6 &
h av e a p p e a re d , t o g e t h e r w i th more th a n
one h u n d red and f i f t y p a p e r s . A d i s c u s s i o n o f th e mechanism
o f th e W i t t i g r e a c t i o n w i l l be fo u n d below ( p . 83 ) and h e r e
i t s g e n e r a l a p p l i c a t i o n s w i l l be d i s c u s s e d .
I n th e W i t t i g r e a c t i o n a k e to n e o r a ld e h y d e i s
r e a c t e d w i th a p h o sp h o ra n e to g iv e an o l e f i n and a p h o sp h in e
o x id e . The c a r b o n y l compound may c o n t a i n any o f th e f o l lo w in g6 3 6 3 6 9 6 4
g r o u p s : - h y d ro x y , a c e to x y , m ethoxy , a c e t a l ,64 66 66
t e t r a h y d r o p y r a n y l , d im e th y la m in o , t e r m i n a l a c e t y l e n i c ,43 43 6 6
h a lo g e n , e s t e r and n u c l e a r h a lo g e n and n i t r o .
The r e a c t i o n h a s p r o b a b ly fou nd m ost u se i n p o ly e n e6 7’ 6 8 6 9
s y n t h e s i s . S g u a le n e , V i ta m in A e s t e r , l y c o p e n e ,6 9 6 9
1 5 , 1 5 * -d eh y d r0- l y c o p e n e , 1 5 ,1 5 *- c i s - l y c o p e n s ,6 9 7?0
1 5 , 1 5 *- d e h y d r 0- 0 - c a r o t e n e and n o r b i x i n and c r o c e t i n d i e s t e r s
h av e b e e n p r e p a r e d u s i n g th e W i t t i g r e a c t i o n .
-2 0 -
The r e a c t i o n h a s b e en u s e d e x t e n s i v e l y i n th e
V ita m in D f i e l d . C a l c i f e r o l and o t h e r r e l a t e d s t e r o i d s have
b e e n p r e p a r e d f o r u se i n l i g h t a b s o r p t i o n s t u d i e s by m ethods6 2 , 6 8
i n v o lv i n g W i t t i g r e a c t i o n s .26
Bestm ann h a s u se d th e W i t t i g r e a c t i o n to
s y n t h e s i s e t r i t i a t e d o l e f i n s w i th p h o s p h o ra n e s h a v in g a
t r i t i u m atom a s th e m e th y le n e c a rb o n a tom . T hese p h o sp h o ra n e s
were p r e p a r e d by t r e a t i n g th e c o r r e s p o n d in g n o n - t r i t i a t e d
phosphonium s a l t w i th sodium e th o x id e i n t r i t i a t e d e t h a n o l : -
PhaP-C H gR > PhaPdCER + EtOHEtOT
Ph&P=GTR ^-------------} PhaP-GHTR + EtO~
I R*CHO
R»CBI= GTE
4A l i é n é s hav e a l s o b e en p r e p a r e d . S t a u d in g e r and
71. 72W i t t i g r e a c t e d k e te n e s w i th p h o s p h o ra n e s , w h i le Gilman
u s e d th e p h o sp h o ra n e (37 ) and k e to n e s t o g iv e a l i é n é s .
P h sP = 0 = CR= R® Hr R ^ R ^ C sO R^R*G= G = GR^R^ 4 PhoPO
(37)
L e v i n e , W i t t i g ^ * and Z b i r a l^ ^ have shown t h a t
-2 1 -
th e W i t t i g r e a c t i o n c a n be u s e d a s an a l t e r n a t i v e t o th e
g l y c i d i c e s t e r s y n t h e s i s , f o r th e c o n v e r s io n o f an a ld e h y d e
o r k e to n e i n t o i t s n e x t h i g h e r hom ologue. A ld e h y d e s and
k e to n e s r e a c t w i th m e th o x y m e th y le n e t r ip h e n y lp h o s p h o ra n e s t o
g iv e v i n y l e t h e r s , w hich a r e r e a d i l y h y d r o ly s e d by a c i d t o
a ld e h y d e s .
PhgiP= CHCOCH» * R*R®C=0 -» R=^E®C= CHCOCH;3
/R^R®Cai.CHO
76S i e m i a r t y c k i h a s u s e d c e r t a i n s u b s t i t u t e d b e n z y l i d e n e -
p h o s p h o ra n e s a s s e l e c t i v e r e a g e n t s f o r th e d e t e r m i n a t i o n o f
a ld e h y d e s .
R e c e n t ly f l u o r o o l e f i n s h av e b een p r e p a r e d by a77 ,78
m ethod w hich i n v o l v e s t h e W i t t i g r e a c t i o n . When a
p h o s p h in e , a c a r b o n y l compound and sodium d i f l u o r o c h l o r o -
a c e t a t e a r e h e a t e d i n a p o l a r s o l v e n t d i f l u o r o o l e f i n s a r e
p ro d u c e d . The d i f l u o r o c a r b e n e p ro d u c e d f r o n th e sodium s a l t
p re s u m a b ly r e a c t s w i th th e p h o sp h in e to g i v e t h e p h o sp h o ra n e
(3 8 ) w hich t h e n u n d e rg o e s a n o rm al W i t t i g r e a c t i o n t o g iv e
th e p r o d u c t s .PhgP
GlCPg -CDONa GOg + NaCl + :GFg --------- > Phg P = CPg(3 8 )
I R a C ORgC = GPg + PhgPO
-2 2 -
( h ) O th e r R e a c t i o n s o f P h o s p h o ru s Y l ld s P ro c e e d in g
v i a I n t e r m e d i a t e B e t a i n e s .
The W i t t i g r e a c t i o n i s a s p e c i f i c exam ple o f a
g e n e r a l r e a c t i o n o f p h o sp h o ru s y l i d s p r o c e e d in g th ro u g h an
i n t e r m e d i a t e b e t a i n e ( 3 9 ) .
+ —Ra.,P=CHE + X = Y R g P - C H R - X - Y
i (3 9 )
p r o d u c t s
A lth o u g h p h o sp h o ra n e s r e a c t by th e no rm al W i t t i g
r o u t e w i th a y 0 - u n s a t u r a t e d k e to n e s i n m ost c a s e s , some
a n o m a l ie s , i n v o lv i n g 1 , 4 - a d d i t i o n , have b e en fo u n d . I n t h e s e
c a s e s th e b e t a i n e (40 ) i s i n i t i a l l y p ro d u c e d , w hich can
decompose i n v a r i o u s ways d e p e n d in g upon th e g ro u p s R.
ft* R*\ R ® I
C
■I — ^ I *CH ^ ( ' - ^ P P b a CH P P h j
I IR i
(ao)
-2 3 -
When ( 4 0 ) i s d e r i v e d from th e r e a c t i o n o f 1 oxo-1,5
d i p h e n y l p e n t - 2 ,4 - d i e n e ( 4 l ) and s t y r y l i n e t h y l e n e t r i p h e n y l -
p h o sp h o ra n e i t decom poses t o g iv e th e t r i e n e ( 4 2 ) ,79
p h e n y la c e ty le n e and t r ip h e n y lp h o s p h in e o x id e .
Ph
( 4 1 )CH 3 0
P h - GH= CH - GH ^PPhokT ^
GH
PhGH = CH
Ph
PhGH = GH- GH
^ GHI
GH= GH
PPhe
Ph/
P h - CH= C H - GH = C H - GH= CH- Ph
+ (42 )
P h-C sG H + PhgPO
vVhen (40) i s d e r i v e d from 2 -m e th y le n e c y c lo h e x a n o n e and
c y c l o h e x y l i d e n e e t h y l id e n e t r i p h e n y l p h o s p h o r a n e any r e a r r a n g e m e n t
s i m i l a r t o t h a t above w ould p ro d u c e c y c lo h e x y n e . As t h i s i s
u n fa v o u ra b le th e d e c o m p o s i t io n f o l lo w s a d i f f e r e n t p a th80
l e a d in g to th e t r i e n e (4 3 ) and t r i p h e n y lp h o s p h i n e o x id e ,
p r o d u c t s w h ich can be e x p l a i n e d by a 1 ,3 h y d r i d e s h i f t .
-2 4 -
,CH:
C \ /P P h 3
+ P113PO
The t h i r d and f i n a l r e c o r d e d exam ple o f c o n ju g a te a d d i t i o n
o f a p h o sp h o ra n e t o a n u n s a t u r a t e d k e to n e h a s b e en81 .
d e m o n s t r a te d by F reem an. When m e th y le n e t r ip h e n y lp h o s -
p h o ran e r e a c t s w i th b e n z y l id e n e a c e t o m e s i t y l e n e (44)*
t r ip h e n y lp h o s p h in e i s e l i m i n a t e d and th e c y c lo p ro p a n e d e r i v a t i v e (4 6 ) i s p ro d u c e d . T h is may be e x p l a i n e d by
e l e c t r o n s h i f t s a s shown i n ( 4 5 ) .
—25'“
P h
CHl)
' ^ P P h a ^
(4 4 )
PhOH GH
P h
PhgP
CHgGH
CH GGHg-
(4 6 )
GH
C o n s id e r a b le work h a s b e en c a r r i e d o u t on th e r e a c t i o n s o f82
e p o x id e s w i th p h o sp h o ru s y l i d s . Denney and B o sk in h av e
shown t h a t e th o x y c a r b o n y lm e th y le n e t r ip h e n y lp h o s p h o r a n e and
s t y r e n e o x id e g i v e , a t 200*0, t r ip h e n y lp h o s p h i n e o x id e
and th e c y c lo p ro p a n e (4 7 ) ( 2 3 ^ ) .
Phg P = GH - GOOEt. + P h - G H - GHg
^ 0P h - GH - GHg + PhgPO
\ /^GH
IGOOEÿ
(4 7 )
McEwan83
fo u n d t h a t when th e o p t i c a l l y a c t i v e phosphonium
-2 6 -
s a l t (4 8 ) was c o n v e r t e d to th e p h o s p h o ra n e , and t r e a t e d
w i th s t y r e n e o x id e , a p r e c i p i t a t e was fo rm e d . T h is was
shown to be th e l i t h i i m i o d i d e a d d u c t o f th e b e t a i n e (4 9 ) •
P h Ph Ph Q-
1+ *■ 1 . L iP h 1 + 1 /CHa— P — CHa------- P h ------------------------------GHg-------P -------GH------ GHg GH
I 2 . Pb-GH-GHa I \I T - \ / ' PhCsHa ^ ^ 0 GgHa
( W ) (4 9 )
When t h i s was h e a t e d t o 190-200*0 f o r t h r e e h o u r s a com plex
m ix tu r e o f p r o d u c t s r e s u l t e d , i n c l u d i n g ra c e m ic e th y l m e t h y l -
p h e n y lp h o s p h in e (3 9 ^ ) and b e n z y la c e to p h e n o n e (5 0 ) ( 1 2 - 3 0 ^ ) .
Use o f i s o t o p i c a l l y l a b e l l e d c a rb o n i n th e phosphonium s a l t
( 4 8 ) , a t th e p o s i t i o n s t a r r e d , p r o v e d t h a t t h i s k e to n e c o u ld
n o t hav e a r i s e n v i a th e s y m m e tr ic a l i n t e r m e d i a t e ( 5 l ) s i n c e
th e l a b e l l e d c a rb o n was fo u n d o n ly a t th e p o s i t i o n (3 t o th e
c a r b o n y l g rou p
-2 7 -
CRr
PhIP
Ph __0 + *0 \
HGH CH— Ph
CgHg\
(4 9 )
GH,
P h - C - G H g -O H Ph
0II
P h ^ ^ ^ C H g ^ P h \
(5 1 ) IJ PhMeEtP
/ U P h ^ - G H s - C - P h
BH
P h - G - G H g - C H g P h
BH
P h - GHg - GHg
0- & - P h
(5 0 )
When h e n z y l id e n e t r ip h e n y lp h o s p h o r a n e was u s e d i n t h i s r e a c t i o n ,
v e r y l i t t l e o f th e k e to n e (50 ) was p ro d u c e d , t h e m ain p r o d u c t s
b e in g t r ip h e n y lp h o s p h in e ox ide (,8C^) and 1 ,3 - d i p h e n y lp r o p e n e .84
Work by Z b i r a l h a s c o n f i rm e d t h i s and a l s o shown t h a t
p -m e th o x y p h e n y le th y le n e o x id e r e a c t s w i th t h i s p h o sp h o ra n e to
g iv e l - p - m e th o x y p h e n y l - 3 -p h e n y lp ro p e n e , th u s e s t a b l i s h i n g th e
p o s i t i o n o f th e d o u b le bond i n r e l a t i o n to t h e p h e n y l g ro u p s .
PhgP = GHPh + p-MeO-GgH* - GH - GHg
p - MeO — Cg Ht — GH = C2I— GHg, — Ph
Z b i r a l h a s a l s o shown t h a t c y c lo h e x e n e o x id e r e a c t s w i th
—28—
b e n z y l id e n e t r ip h e n y lp h o s p h o r a n e t o g iv e th e o l e f i n ( 5 2 ) and
th e h y d ro c a rb o n ( 53 )
Ph3.P=GHPh; ♦ -> P h -C m = Œ —
+
0 “(52 )
(5 3 )
A l l t h e s e r e s u l t s may be e x p la in e d i n th e f o l lo w in g
m anner . The i n i t i a l r e a c t i o n i n a l l c a s e s i s n u c l e o p h i l i c
a t t a c k o f th e a ^ c a r b a n io n i n th e p h o sp h o ra n e on th e ep o x id e t o
g iv e th e b e t a i n e ( 5 4 ) . When = a l k y l th e e l e c t r o p h i l i c
c h a r a c t e r o f th e p h o sp h o ru s i n th e b e t a i n e i s d e c r e a s e d , th u s
h i n d e r i n g a t t a c k o f 0 s u f f i c i e n t l y t o a l lo w a 1 ,3 h y d r id e
s h i f t t o t a k e p l a c e , l e a d in g to t h e k e to n e ( 5 5 ) and th e
p h o sp h in e R^gP.
■ " - U\ +
R=^3:P = CHE®- + R®CE — CHE* E ^ g P y CHE* - CHE®
R'
(5 4 )
E^3 P + E ® C % .CÏÏR3 .COE*.
(55)
—29—
85A s i m i l a r r e a c t i o n h a s b e e n r e p o r t e d by W i t t i g and B o l l .
B u ty ra ld é h y d e r e a c t s w i th b u to x y m e th y le n e t r ip h e n y lp h o s p h o ra n e
t o g iv e th e b e t a i n e ( 5 6 ) w hich u n d e rg o e s a 1 ,2 h y d r id e s h i f t
t o g iv e th e k e to n e ( 5 7 ) and t r ip h e n y lp h o s p h in e .
PhaP= CH - OBu
+
G3H7 - GHG
PhgPyGH i-G Bu
IGg H7
( 56 )
PhgP+
GHg, - 0 - B u
0 = 0
Cg Ht>(5 7 )
I n a l l o t h e r o a s e s c y c l i s a t i o n o c c u r s t o g iv e (58 ) w h ich can
th e n u n d e rg o e i t h e r P —C o r 0 —G f i s s i o n .
0GHR-
R% P
(5 8 ) GHR'
GHR® /
(B)
GHR® ^
•QR^.,P
CHR*
GHR® (5 9 )
r /“ g h e ®
\ CHE*E%,PO + / \ ^
E®GH-— >CHE®
E^aPO + GHR® = CE®-GHgE*
( 60)
-3 0 -
When s t a b l e p h o sp h o ra n e s a r e i ised w i l l be a n e l e c t r o n
w ith d ra w in g g roup and w i l l be a b l e t o s t a b l i s e th e c a r b a n io n
( 5 9 ) , th u s i n th e c a s e o f s t a b l e p h o sp h o ra n e s p a th (A) to g iv e
th e c y c lo p ro p a n e w ould be e x p e c te d . I n o t h e r c a s e s p a th (Bl)
w i l l be f o l lo w e d p ro d u c in g th e o l e f i n ( 6 0 ) , e x c e p t where R^
and R® a r e h e l d i n a f i x e d c o n fo r m a t io n such t h a t R® i s t r a n s
to th e 0 — C bond . T h is i s th e c a s e i n th e i n t e r m e d i a t e ( 6 l )
from c y c lo h e x e n e o x id e , and th e r e a r r a n g e m e n t shown can ta k e
p l a c e l e a d in g t o th e o l e f i n (62 )
R
CH
(61) R -G H = CH
(62)C e r t a i n p h o sp h o ra n e s c an th e m s e lv e s e x i s t i n a b e t a i n e fo rm .
T h is i s th e b a s i s o f th e a c e ty l e n e s y n t h e s i s o f T r i p p e t t and , 8
Gough. One c o n t r i b u t i n g s t r u c t u r e i n p -k e to p h o s p h o ra n e s c an
be c o n s id e r e d t o be th e p h o s p h o b e ta in e form (6 3 ) ( s e e p . 3 )
and an h e a t i n g to ^ 200®G t h e s e compounds e l i m i n a t e p h o sp h in e
o x id e to g iv e th e c o r r e s p o n d in g a c e t y l e n e .
-3 1 -
/ R "
l \ ^ l l ■ - — Ra. PO + IIV C C
■O V A:
(6 3 )
F o r th e y i e l d s t o be good i n t h e s e r e a c t i o n s o r R®
m ust be a b l e t o c o n ju g a te w i th th e d o u b le bond i n th e
b e t a i n e (Ri o r Rg = -P h , -COR, -GOOR, -C N ), t h i s i s
p r o b a b ly b e c a u s e th e a c e t y l e n e fo rm ed r e q u i r e s t o be
s t a b l i s e d somewhat to s u r v i v e th e r e a c t i o n c o n d i t i o n s .86
Zimmerman h a s p y r o ly s e d t h e p h o sp h o ra n e (64 )
a t 220-260®C t o g iv e th e e x p e c te d a c e t y l e n e ( 6 5 ) and th e
m uconic e s t e r ( 6 6 ) .
Pho 5 COOMe MeOOC - C = C - ( CHg ) — COOMe^ (6 5 )
II 220°C +G C%
“ 0 CHa COOMe Me03C-CH = CH-CH = CH-COOMe
( 6 4 ) (6 6 )
The r e a c t i o n o f p h o s p h in e s w i th £ -b e n z o q u in o n e s l e a d s t o
b e t a i n e ( 6 7 ) a n a lo g o u s t o ( 6 3 ) . T hese a r e e x t r e m e ly
-3 2 -
t h e r m a l ly s t a b l e and w i l l n o t e l i m i n a t e p h o sp h in e ox ide
even a t t e m p e r a tu r e s >280°G .
(67);
The r e a c t i o n o f p h o s p h o ra n e s w i th p h e n y l i s o c y a n a te was
f i r s t r e p o r t e d by S t a u d i n g e r , and h a s s i n c e b e en f u l l y89
i n v e s t i g a t e d by T r i p p e t t . The g e n e r a l r e a c t i o n may be
f o r m u la te d a s a t y p i c a l W i t t i g r e a c t i o n p ro c e e d in g v i a th e
b e t a i n e ( 6 8 ) . When and R^ a r e p h e n y l , th e b e t a i n e (6 8 )
e l i m i n a t e s p h o sp h in e o x id e to g iv e 1 , 1 - d i p h e n y l - 2 - p h e n y l -
im id o e th y le n e (6 9 ; R = R® = P h ) .
l^R^
PHqP
R^R^G C II + II
NPh
, R"^R®C-7-C^ ' - V I
• / 0P h g P + ^ J
H
Ei^O -C -H H Ph
;HPh
(68)
R^R^C= C = NPli
(6 9 )Phg P 0
(70)
-3 3 -
However i f o r R® a r e h y d ro g en a p r o t o n t r a n s f e r t o
n i t r o g e n o c c u r s , t o g iv e th e more s t a b l e p h o sp h o ra n e ( 7 0 ) .
N i t ro s o b e n z e n e a l s o r e a c t s w i th p h o s p h o ra n e s v i a
a n i n t e r m e d i a t e b e t a i n e (71 ) to g iv e p h o sp h in e o x id e and90
S c h i f f * s b a s e .
Phg^P = GHR Pho P . Pho PO
j - r -
^ ^ N P h4 +
CURIINPh
0 = N - P h 0
(71 )
T h is r e a c t i o n a p p e a r s t o be g e n e r a l f o r s t a b l e and
u n s t a b l e p h o s p h o r a n e s , how ever p -d im e th y la m in o n i t r o s o b e n z e n e
h a s been shown t o g iv e p h o s p h in e , and w hat i s th o u g h t t o be91
th e n i t r o n e ( 7 2 ) , w i th p h o sp h o ru s y l i d s . T h is i s
p re su m a b ly due t o t h e + M e f f e c t o f th e £ - d im e th y la m in o
g roup f a c i l i t a t i n g th e e l e c t r o n s h i f t s shown i n ( 7 3 ) .
. / = \ I ■ / = v ?■(C H 3 )2 N -^ ^ ^ N - j -CHR -♦ PhaP + (C H 3 )a N -^ ^ ^ H = C H R
(7 3 ) (7 2 )
Garbon d i s u l p h i d e r e a c t s w i t h p h o sp h o ra n e s t o g iv e
t r i p h e n y lp h o s p h i n e s u l p h i d e and t h i o k e t e n e s , * p re s u m a b ly
-3 4 -
v i a th e b e t a i n e (.74) •
Pho P = GRg + GSja -> Pho;P,TT“ CRg Rg C = C = S_ +
8 — 0 = 8 PhoPS
(74)
92Bestm ann and Seng h av e shown t h a t p h o sp h o ra n e s r e a c t
w i th S c h i f f ’ s b a s e s by two d i f f e r e n t r o u t e s d e p en d in g on
th e p h o sp h o ra n e . When p h o sp h o ra n e s o f th e ty p e ( 7 3 ) , w i th
a — CHg — g ro u p i n th e p - p o s i t i o n o f t h e s i d e c h a i n , were
r e a c t e d w i th b e n z y l i d e n e a n i l i n e th e p r o d u c t s w ere p h o s p h in e ,
a n i l i n e and a l i é n é s o f th e ty p e ( 7 6 ) .
P h o P = GH-GHg - R + P h “ C H =N P h P hgP + PhNHg+PhCH = G = GHR
(7 5 ) (7 5 )
As y e t no m echanism h a s b e e n p o s t u l a t e d f o r t h i s r e a c t i o n .
When th e p h o sp h o ra n e i s o f t h e ty p e ( 7 7 ) , w i th
no p — GHg — g r o u p , t h e e l i m i n a t i o n p r o c e e d s v i a th e b e t a i n e
(7 8 ) to g iv e th e im in o p h o sp h o ra n e (7 9 ) and th e o l e f i n (8 0 ) ,
-3 5 -
PhgPs.P h a P = C H - R + H^CH = NPH -* + T^CH
(77 )(78)
CHPh '^R^
Pha,P = NPh ( 7 9 ) +
RCH = CHRi
(80)
Bestm ann h a s a l s o s t u d i e d th e a u t o x i d a t i o n o f p h o s p h o ru s9 4, 9 6, 96
y l i d s . B e n z y l id e n e t r ip h e n y lp h o s p h o r a n e (8 1 ; R = P h )
r e a c t s w i th oxygen to g iv e t r i p h e n y lp h o s p h i n e o x id e ( 8 0 ^ ) ,
c i s - s t i l h e n e (2 0 ^ ) and t r a n s - s t i l b e n e (35% ).
The i n i t i a l s t e p i s p o s s i b l y th e f o r m a t io n o f th e b e t a i n e
( 8 2 ) , d e c o m p o s i t io n o f which l e a d s t o p h o sp h in e o x id e and
b e n z a ld e h y d e w hich c a n th e n r e a c t w i t h th e o r i g i n a l p h o s
p h o r a n e , by a n o rm al W i t t i g r e a c t i o n , t o g iv e s t i l b e n e
(8 3 ; R = P h ) .
P hgP = CHR ____ . P h g V PhgPO
+ (8 1 ) . Vy(8 2 )
R— CHO
PhgP= CHR
Phg.PO + RCH - CHR
(83)
-3 6 -
S ty r y lm e th y le n e t r ip h e n y lp h o s p h o r a n e (8 1 ; R = P h —CH = CH— )
s i m i l a r l y gave 1 ,6 - d i p h e n y l h e x a t r i e n e (83 ; R = P h —GE= GH—) .
T h is r e a c t i o n h a s c o n s i d e r a b l e a p p l i c a t i o n s i n p o ly e n e96
s y n t h e s i s and Bestm ann h a s c o n v e r t e d v i t a m in A i n t o
g_-ca ro ten e i n 35^ y i e l d by th e f o l lo w in g m ethod .
GHjjOH>
HX
CHsPPhg
1 . B ase
R# Og
C y c l i c o l e f i n s , i n c l u d i n g a c e n a p h th y le n e (8 U ), h av e b e e n96
p r e p a r e d by a u t o x i d a t i o n o f b i s - p h o s p h o r a n e s .
-3 7 -
CH = PPh.
(8 4 )
The a n a lo g o u s r e a c t i o n o f p h o s p h o ra n e s w i th s u lp h u r l e a d s
to p h o sp h in e s u l p h i d e s and t h i o k e t o n e s .
S t a b l e p h o s p h o ra n e s (8 5 ) have a l s o been o x i d i s e d97
w ith p e r a c e t i c a c i d t o g iv e o l e f i n s , p r o v id in g = H.
wCHaCOaH
PhoE = CR^E® ---------------^I n
CaJaCOOH
PhaPO + R^R®G = CRiR®
(8 5 )
Thus e th o x y c a r b o n y I m e th y le n e t r ip h e n y Ip h o s p h o r a n e
(8 5 ; = H, R® = —COOEt) gave d i e t h y l f u m a r a t e ( 4 3 ^ ) , b u t
a - e t h o x y c a r b o n y le t h y l i d e n e t r ip h e n y lp h o s p h o r a n e (8 5 ; R ^ = Me ,
R® = — COOEt); gave o n ly 1% o f th e e x p e c te d o l e f i n . When l e s s
s t a b l e , more b a s i c , p h o sp h o ra n e s were u s e d i n t h i s r e a c t i o n
phosphonium a c e t a t e s w ere fo rm ed , w h ich u n d e rw en t h y d r o l y s i s
to th e p h o sp h in e o x id e .
When b e n z o y lp e ro x id e was u s e d a s th e o x i d i s i n g
a g e n t , a c i d a n h y d r id e s o f th e ty p e (8 6 ) were fo rm ed .
-3 8 -
0 0I I
PhoP= C H - C O - P h + 2 P h - G - O - O - G - P h
-» PhgPO + CPhCO)a.O + PhGO - 0 - GO - GHPh
0 - GO- Ph( 86)
A p o s s i b l e m echanism f o r t h i s r e a c t i o n i n v o lv e s th e
i n i t i a l p r o d u c t i o n o f th e phosphonium s a l t ( 8 7 ) , a t t a c k
o f b e n z o a te on t h i s to g iv e th e b e t a i n e (88 ) and e l i m i n a t i o n
o f p h o sp h in e l e a d i n g t p (8g)^ which r e a r r a n g e s t o t h e p r o d u c t
( 86).
PhGOO"
Phg P = GH-GO - Ph + (PhGOO)a -*■ Ph - GO - GH— PPhg
0 -G -P h (87 )
n► P h — G — GH-T-PPhQ
/ \ ^ Ph-CO—-0 0 — C — Ph
n0
( 88)
Ph—GO—0
A+ PhaP
0 - GO - Ph
(8 9 )
P h - G B - GO - 0 - GO - Ph P h - G O - 0
( 86)
The t r i p h e n y lp h o s p h in e i s o x i d i s e d by th e s e c o n d m o le cu le
-3 9 -
o f p e ro x id e and i s o l a t e d a s t h e o x id e . An a l t e r n a t i v e
e x p l a n a t i o n i s t h a t th e b e t a i n e (8 8 ) e l i m i n a t e s p h o sp h in e
o x ide to g iv e an o l e f i n , w h i c h i s e p o x id i s e d by th e se c o n d
m o le c u le o f p e ro x id e to ( 8 9 ) .99
Z b i r a l h a s o x i d i s e d p h o sp h o ra n e s w i th l e a d
t e t r a a c e t a t e t o g iv e p h o s p h in e o x id e s and c a r b o n y l com pounds.
Pb(OAc)*P h a = C - G O - R > RCO'COOMe + PhoPO
OMe
O z o n o ly s is o f ^ - k e t o a l k y l id e n e p h o s p h o r a n e s l e a d s 100
t o a - d i k e t o n e s . When t r e a t e d w i th ozone a t -70® i n
m e th y len e c h l o r i d e , p h e n a c y l i d e n e - t r ip h e n y lp h o s p h o r a n e gave
96^ o f t r i p h e n y lp h o s p h in e o x id e and 88^ o f p h e n y lg ly o x a l ( 9 0 ) .
O3Pho P = CH - CO - P h ------------- > Pha PO + FhCO • CHO
CHgClg-70® C ( 9 0 )
10a.M ark l h a s c a r r i e d o u t t h e r e a c t i o n o f b e n z y l id e n e -
t r ip h e n y lp h o s p h o r a n e w i th a l i p h a t i c d iazocom pounds. The
b e t a i n e (9 2 ) was i n i t i a l l y fo rm ed , e l i m i n a t i o n o f t r i p h e n y l
p h o sp h in e t h e n gave th e a z i n e ( 9 3 ) . The t r i p h e n y lp h o s p h i n e
e l i m i n a t e d was a b le to r e a c t w i th a n o th e r m ole o f d i a z o
compound t o g iv e th e p h o s p h in e a z in e ( 9 4 ) »
-4 0 -
+ +Pha p = c m + R2 C 0 « C E - f = I l -» Pha P jC H R
(9 1 ) A - H = GREGOR®
I (9 2 )
, , R®COCEl=K * ,Pha = R - H = CR^COR® *------------------- Pha.P + RCH = N - K = CR GOR®
(9 4 ) (9 3 )
M ark l c la im e d t h a t th e more s t a b l e p h o sp h o ra n e s (9 1 ;
R= — GOOGHs, — CO —P h, —GO—CHa) d id n o t r e a c t w i th
a l i p h a t i c d ia z o compoimds. S t r y e l e c k a , S i e m i a t y c k i , and 102
P r é v o s t h a v e , h ow ever, r e p o r t e d t h a t h e n z o y l d i a z o -
m ethane and p h e n a c y l id e n e t r ip h e n y lp h o s p h o r a n e (91 ; R = — COPh)
r e a c t to g iv e 4 - h e n z y l id e n e - 2 ,6 - d i p h e n y l p y r a n (95 ) and
t r ip h e n y lp h o s p h in e o x id e . GHPh
2Ph3? = CHCO- Ph 4f PhCO-CHNa
PhPh
4r PhoPO
(9 5 )
P y r i l i i m s a l t s (96 ) have b e e n shown to r e a c t w i th p h o sp h o ru s1 03
y l i d s t o g iv e s u b s t i t u t e d benzene d e r i v a t i v e s by a
m echanism in v o lv in g a W i t t i g ty p e e l i m i n a t i o n .
-4 1 -
+ 2 P h s P s CHR
+
BF%
(9 6 )
^ r3 P h o P -C H g R B P ^
R3
PhaPO
R3
104D im ro th , W olf and Wache have e x te n d e d t h i s r e a c t i o n
to th e p r e p a r a t i o n o f a z n le n e d e r i v a t i v e s by u s in g o n ly
h a l f a mole eg_u iva len t o f p h o sp h o ra n e .
"42-
R2
R2fj %PhoP=CH« p Q
" ^ 0 ^ ^ j ' ^+
b p : R"
B f ' (97 )
0 R3
PPho
p i + PhgP
<R0 — \ R " ' " C
ii r p p h o
R2-VI.
b c
P P h ,
( 98)
-4 3 -
The a u th o r s s u g g e s t t h a t th e I n t e r m e d i a t e (97 ) i s
i n i t i a l l y fo rm ed , w h ich , on r i n g o p e n in g , a l d o l c o n d e n s a t io n ,
t r a n s a n n u l a r r e a r r a n g e m e n t and l o s s of w a te r l e a d s to th e
a z u le n e ( 9 8 ) .
P h o sp h o ra n e s a l s o g iv e a d d u c t s w i th e l e c t r o n 106 ,1.06
d e f i c i e n t compounds, e . g . d ib o ra n e r e a c t s w i th+ —
m e th y le n e t r ip h e n y lp h o s p h o r a n e to g iv e PhgP — CHg — BH3 .
T hese a d d u c t s a r e s t a b l e t o w a te r , b u t l i b e r a t e h y d ro g e n
on t r e a t m e n t w i th d i l u t e a c i d . D ecaborane and b o ro n
t r i f l u o r i d e g iv e s i m i l a r s a l t s .
(c ) R e a c t i o n s o f P h o sp h o ru s Y l id s n o t P ro c e e d in g
v i a I n t e r m e d i a t e B e t a i n e s .
R e a c t io n s o f t h i s ty p e may be r e p r e s e n t e d b y : -
R a P = C H E * X - Y -+ E a f - C H R - X + Y "
A l l p h o sp h o ru s y l i d s a r e L ew is b a s e s and a s su ch w i l l r e a c t
w i th i n o r g a n i c a c i d s to g iv e t h e c o r r e s p o n d in g phosphonium
s a l t .
P h g P s CHa + HCl PhoP-CHa. C l”1 07
B estm ann h a s s t u d i e d th e s t a b i l i t y o f p h o sp h o ra n e s an d
shown t h a t an e q ^ u i l l ib r iu m i s e s t a b l i s h e d b e tw een a
p h o sp h o ra n e and a phosphonium s a l t :
-4 4 -
Pha P - CHg - R X" + Pha;P = CHR^ # Phg P = CHR + PI13 P - CHg-R^^ X"
T h is r e a c t i o n i s known a s t r a n s y l i d a t i o n ( s e e p . 6 )
and th e e g u i l l i h r i u m l i e s to w a rd s th e m ost s t a b l e , l e a s t
b a s i c , p h o sp h o ra n e .
P h o sp h o ru s y l i d s u n d e rg o h y d r o l y s i s , t h e l e a s t
s t a b l e i n c o ld w a te r , th e more s t a b l e i n b o i l i n g w a te r o r
a l k a l i , t o g iv e th e c o r r e s p o n d in g h y d ro c a rb o n o f t h a t
g roup a t t a c h e d to th e p h o sp h o ru s which i s m ost s t a b l e a s
an a n io n , and a p h o sp h in e ox ide*
Ph3;P = CHR + HgO P h o P - C H g - R OH”
0 iIIPhgPCHgR + PhH
Only c y c lo p e n t a d i e n y l i d e n e t r i p h e n y l p h o s p h o r a n e i s
u n e f f e c t e d by t r e a tm e n t w i th h o t a l k a l i .
The a l k y l a t i o n o f p h o sp h o ra n e s h a s a l r e a d y b e e n
d i s c u s s e d (p* é ) • Work h a s a l s o b e e n c a r r i e d o u t on sy s te m s
where a l k y l a t i o n and W i t t i g e l i m i n a t i o n s h o u ld be c o m p e tin g
r e a c t i o n s . I n m ost c a s e s th e W i t t i g r e a c t i o n i s more
f a v o u r a b l e . When 4 -h a lo m e th y lb e n z a ld e h y d e i s r e a c t e d w i th
s u b s t i t u t e d b e n z y l id e n e t r i p h e n y l p h o s p h o r a n e s , s u b s t i t u t e d1 08
s t i l b e n e s a r e fo rm ed .
-4 5 -
CHO
+ P h g P = C a - G g H t - R -+ X - C H g - Z ~ ^ - C H = C E - C e H * -R
CHaX
S i m i l a r l y a -b ro m o p ro p io n a ld e h y d e r e a c t s w i th e th o x y c a r b o n y l -
m e th y le n e t r ip h e n y lp h o s p h o r a n e to g iv e th e a , p - u n s a t u r a t e d^ 109
e s t e r (,99) i n GLj y i e l d .
CHa.CHBr.CHO + Phg^P = CH.COOEt CHa. CHBr. CH = CH. COOEt +PhaPO
(9 9 )
110B estm ann h a s c a r r i e d o u t a s e r i e s o f r e a c t i o n s w i th
a -b ro m o k e to n e s and m e th o x y c a r b o n y lm e th y le n e t r ip h e n y lp h o s -
p h o r a n e . K e to n es w i l l n o t underg o W i t t i g r e a c t i o n s w i th
s t a b l e p h o sp h o ra n e s u n d e r th e c o n d i t i o n s o f th e r e a c t i o n and
so t h e f i r s t s t a g e i s a l k y l a t i o n o f th e p h o sp h o ra n e to g iv e
th e phosphonium s a l t ( lO O ) . A se c o n d mole o f p h o sp h o ra n e
th e n rem oves a p - p r o t o n t o g iv e th e b e t a i n e ( l O l ) ,w h i c h
e l i m i n a t e s t r ip h e n y lp h o s p h in e t o g iv e th e o l e f i n (1 02 ) i n
60 -8 0 ^ y i e l d .
E - C O - CHgBr + Phg P = CH- COOCHa Phg P - C H - COOCH3
B r” GHg — C 0 — R
I (100)PhaP + RCOCH= CHCOOCH3 -f P h o ^ C H — COOCH3
-46 -
111S ie m ia ty c k î and S t r y e l e c k a have c a r r i e d ou t th e
a n a lo g o u s r e a c t i o n b e tw ee n p h e n ac y lb ro m id e and ph en a-
c y l i d e n e t r i p h e n y lp h o s p h o r a n e . They fo u n d t h a t a s w e l l
a s th e e x p e c te d o l e f i n ( 1 , 2- d i b e n z o y le t h y le n e ) and
p h e n a c y l t r ip h e n y lp h o s p h o n iu m b ro m id e , a 1% y i e l d o f th e
c y c lo p ro p a n e ( 103) was fo rm ed .
PhQP= GHCOPh + PhCOCHgBr -> PhCO.GBI= GH.COPhCOPh
COPh\Pha,P - CHa - COPh +
(103 )
A p o s s i b l e e x p l a n a t i o n o f th e f o r m a t io n o f th e c y c lo p r a n e
d e r i v a t i v e i s t h a t t h e 1 ,2 d ib e n z o y le th y le n e f i r s t fo rm ed
r e a c t s w i th th e o r i g i n a l p h o sp h o ra n e t o g iv e th e b e t a i n e
( 1 0 4 ) . E l e c t r o n s h i f t s a s shown w i l l g iv e th e c y c lo p ro p a n e
and t r i p h e n y l p h o s p h i n e , w hich would be e x p e c te d t o form
th e p henacy lph osp hon ium s a l t w i th th e p h e n a c y lb ro m id e
p r e s e n t i n th e r e a c t i o n m ix tu r e .
Phg P = GHGOPh + PhCO.CH= CE.COPh
— > P h ^ P j GHCOPh ----------> PhgP + GHCOPh
GHCOPh PhCOCH----- — CHCOPh
- CHCOPh
(1 0 4 )
■-47—
The no rm al r e a c t i o n p a t h f o r b e t a i n e s o f th e
ty p e ( 10 4 ) i s a 1 ,3 p r o t o n t r a n s f e r to g iv e th e s t a b l e
p h o sp h o ra n e (105 ) (S ee p . 54 ) how ever th e c y c lo p ro p a n e
i s o n ly p ro d u c e d i n v e r y low y i e l d .
Ph3;P= C R -G H R -C H gR R = - C O - P h
An a l t e r n a t i v e e x p l a n a t i o n i n v o lv e s t h e p r o d u c t i o n o f t h e
c a rb e n e PhCO— CH, p o s s i b l y b y th e a c t i o n o f th e p h o sp h o ra n e
on p h e n a c y l b ro m id e , a n d a t t a c k o f t h i s on th e 1 , 2- d ib e n z o y l -112
e t h y l e n e . B estm ann h a s shown t h a t w h i l e b r o m o a c e ta te s
g iv e o l e f i n and p h o s p h in e , a s a b o v e , c h l o r o a c e t a t e s g iv e
th e c y c lo p ro p a n e d e r i v a t i v e s c o r r e s p o n d in g t o ( 103 ) , w i th
p h o s p h o ra n e s .69
T r i p p e t t h a s shown t h a t 2 -b ro m ocyc lo hexanon e
r e a c t s w i th th e p h o sp h o ra n e ( 106 ) t o g iv e th e t r i e n e ( 107 ) .
-I- P h sP = CH-CHcc(106)
(107)
-4 8 -
As y e t no m echanism h a s b e en s u g g e s te d f o r t h i s
r e a c t i o n , b u t i t i s p o s s i b l e t h a t th e d ie n e (10 8 ) i s f i r s t
fo rm ed by a n o rm a l W i t t i g r e a c t i o n and t h i s i s t h e n
d e h y d ro h a lo g e n a te d by th e p h o sp h o ra n e ( 106 ) .
+ PhQP= O S - CE
( 106)Br
(108)
(107);
+ BH B r
113M arkl h a s r e a c t e d p h o sp h o ra n e s w i th c h lo ro a m in e s o f
th e ty p e ( 1 0 9 ) . The phosphonium s a l t ( l l O ) i s i n i t i a l l y
fo rm ed , and u n d e rg o e s d e h y d ro h a lo g e n a t io n by th e o r i g i n a l
p h o sp h o ra n e to g iv e th e enam ine phosphonium s a l t ( i l l ) .
PhoP=CHR + CHCla-NMes
(1 0 9 )
GHCl- meg; PhsP-CHH(110) Gi
( 110)
PhgP = CHE
CN "FMe*+ II
PhgP - CE G1 + P l ^ P - C H g - E
( 111)
These compounds c an be u s e d t o p ro d u ce a w ide ra n g e o f
-49—
phosphonium s a l t s .114
S e y f e r t h ^ hav e shown t h a t p h o sp h o ra n e s
w i l l r e a c t w i th m e t a l l i c , a n d o r g a n o m e t a l l i c , h a l i d e s to g iv e
s u b s t i t u t e d phosphonium s a l t s o f th e ty p e ( 112 ) .
PheP = CR^R2 + M - B r P h a P -C R ^ R ^ -M Br
( 112)
114 115 , . 114T h is o c c u r s when M= (CH3 ) a 8 i " , Ph@P-, ( CH3 )g 8n - ,
114and PhgGe.
V/hen d i h a l i d e s a r e u se d th e r e a c t i o n g i v e s th e
d i phosphonium s a l t s (1 13 ) f o r M =Zn’*’**’, Hg’*”*',116 , . 114
PhP and ( CH3 ) g 8n .
+ +PhaP= CR^R^ + B r - M - B r PhgP- CR^R^ - M- CR^R^ - PPhg
2Br~
(1 1 3 )
S t a b l e p h o sp h o ra n e s r e a c t w i th h a lo g e n s to g i v e ,
i n i t i a l l y , th e phosphonium s a l t ( l l 4 ) , w h ich t h e n u n d e rg o e s25 , 1 1 7 ,118
t r a n s y l i d a t i o n to g iv e th e p h o sp h o ra n e ( 115 ) .
+ «
PhQ P = CH - COOCH3 + Xg -► Phg P - CHX - COOCH3 XiPhaP= C X - COOCH3
( 115 )
-5 0 -
H a lo g e n a te d p h o sp h o ra n e s a r e u s e f u l f o r the
p r e p a r a t i o n o f v i n y l h a l i d e s by a W i t t i g r e a c t i o n . I f
e x c e s s h a lo g e n i s u s e d th e p h o sp h o ra n e ( 115 ) r e a c t s
f u r t h e r to g iv e t h e phosphonium s a l t
Pha P - CXg - COOGH3 X”
D iazonium s a l t s w i l l r e a c t w i th s t a b l e p h o sp h o ra n e s
to g iv e s a l t s ( I I 6 ) , w h ich may be c o n v e r t e d t o h i g h l y
c o lo u r e d p h o sp h o ra n e s (1 1 7 ) by t r e a tm e n t w i th aqueous119
sodium h y d r o x id e .
PhoPr: CHR + -N .= N X” P h g P - C H R - R = N-R=^x“ (116)
0H~PhaP= C R -N = H - R i
(1 1 7 )
How ever, when b e n z y l id e n e t r ip h e n y lp h o s p h o r a n e v/as r e a c t e d
w i th d iazon iu m s a l t s th e s a l t (118 ) was p ro d u c e d .
P h 3 P - C - K = N - P h X ^ N = N - P l t
( 118)
C y c lo p e n ta d i e n y l id e n e t r ip h e n y lp h o s p h o r a n e a l s o
b e h av e s d i f f e r e n t l y i n t h a t s u b s t i t u t i o n t a k e s p l a c e a t th e
P p o s i t i o n to g iv e the azo dye ( I I 9 ) , w i th b en zen e d iazon iu m
-5 1 -
120c h l o r i d e i n a sodium a c e t a t e b u f f e r .
PhaP — L > PhgP X“ PhaP
N = H - P h N = K - P h
(119)
121A c c o rd in g to S a u n d e rs and Burchmann, p h o sp h o ru s y l i d s
can be re d u c e d w i t h l i t h i u m alum in ium h y d r id e t o p h o s p h in e s .
PhaP= CHR + LiAlH* -* > PhaPCHgR
+ PhH
Even p - k e to p h o s p h o ra n e s can be r e d u c e d i n t h i s
way v ; i th o u t r e d u c t i o n o f t h e c a r b o n y l g ro u p .
Z inc and a c e t i c a c i d a p p e a rs t o work d i f f e r e n t l y ,
r e d u c in g p - k e to p h o s p h o ra n e s to t r i p h e n y lp h o s p h i n e and a122 ,123
k e to n e . The r e a c t i o n i s th o u g h t t o p ro c e e d by
a t t a c k o f z in c on the c a r b o n y l g roup o f th e i n i t i a l l y
fo rm ed , t r a n s i e n t , phosphonium a c e t a t e .
CHa COOH +Phg P = CH*CO*R ---------------> Phg CHg CHq COO
C aZn‘-1 0 I R
HgO ■TRGOGHa ------- ( GHaGOO)Zn(0 - GR = GHg ) + PhaP
—52—
A tte m p ts to e x te n d t h i s r e a c t i o n to th e p r e p a r a t i o n o f1 2 4
P -k e to e s t e r s have f a i l e d .
-5 3 -
The R e a c t i o n s o f P h o sp h o ra n e s
w i th A c t i v a t e d T r i p l e Bonds
A c t i v a t e d m u l t i p l e bonds a r e h i g h l y s u s c e p t i b l e
to n u c l e o p h i l i c a t t a c k . V a r io u s p h o sp h o ru s c o n t a i n i n g
n u c l e o p h i l e s have b e en u se d i n t h i s way, n o t a b l y125
p h o s p h in e s and p h o s p h o ra n e s .126
Jo h n s o n and Tebby have shown t h a t p h o s p h in e s
r e a c t r e a d i l y w i th a v a r i e t y o f u n s a t u r a t e d com pounds,w i th
i n i t i a l f o r m a t io n o f th e M ic h a e l a d d i t i o n p r o d u c t s .
T r ip h e n y lp h o s p h in e r e a c t e d w i th th e d i e s t e r o f a c e t y l e n e -
d i c a r b o x y l i c a c i d to g iv e ( 1 2 0 ) , w hich th e n r e a c t e d w i th
a f u r t h e r m o le c u le o f a c e t y l e n e to g iv e th e 1 , 5 - d i p o l e
( 1 2 1 ) , w hich was i s o l a t e d a s i t s h y d r o i o d id e .
.COOR PhaP .COOR
PbgP + '
COOR
COOR
COOR
COOR
COOR ^COOR ^C O O R
( 120) ( 121)
27 28Oda and Hoffm ann hav e shown t h a t p h o s p h in e s
r e a c t r e a d i l y w i th a c t i v a t e d do u b le b o n d s , a g a i n i n i t i a l l y
fo rm in g th e M ic h ae l a d d i t i o n p r e c u r s o r , a n a l o g o u s to ( 1 2 0 . )
-5 4 -
(See p . 7 ) •
I n th e r e a c t i o n s o f p h o sp h o ra n e s w i th a c t i v a t e d o l e f i n s ,127 ,128
t h r e e p o s s i b l e p a th s h av e b e en s u g g e s t e d , a l l o f
which i n i t i a l l y in v o lv e M ic h a e l a d d i t i o n o f th e p h o sp h o ran e
c a r b a n io n to th e d o u b le bond to g iv e ( 1 2 2 ) .
Ra P = CHR + R®R®G = GR^R® -* RaP - GHR" - GR^R® - GR*R®
( 122)
T h is c a n th e n r e a c t f u r t h e r by;
( a ) a p r o to n s h i f t from th e a - c a r b o n to th e ^ - c a r b o n
to g iv e th e p h o sp h o ran e (123)
Ra P = GR^ - GR2R® - GHR*R®
(123)
(b ) r i n g c l o s u r e and e l i m i n a t i o n o f p h o sp h in e t o g iv e
th e c y c lo p ro p a n e ( 1 2 4 ) ,
^ G H R ^RaP'
GR^R® CRSRS
(124)
and ( c ) i f R® c a n form a s t a b l e a n io n , th e l o s s o f ( R^)
and f o r m a t io n o f ( 125 ) w hich l o s e s a p r o t o n to
g iv e th e p h o sp h o ra n e ( 1 2 6 ) .
-5 5 -
+ l ' a . - +p — nw pi — np3 — m
'R2
R 3 P - CHR - CR - CR*R® -> R 3 P - CHR - CR® = GR*R®
' ( 1. 3 )
Rs P = CR^ - CR® = CR*R®+ (126)
R*H
A i l t h e s e p a th s have b e en o b se rv e d .
These t h r e e ty p e s o f r e a c t i o n a l s o a p p ly when
p h o sp h o ra n e s r e a c t w i th a c t i v a t e d a c e t y l e n e s . H ow ever,
i n t h e s e c a s e s t h e r e i s th e p o s s i b i l i t y o f a f u r t h e r ty p e
o f r e a c t i o n i n v o lv i n g th e f o u r membered t r a n s i t i o n s t a t e
( 127 ) and l e a d in g to th e p h o sp h o ra n e (1 2 8 ) .
RaPsCHR^ + X - C = C - X -, RaP-|-CHR^
- J b y i (1 27)
R3P= csc-cx= c h r '
(1 2 8 )
127 129T r i p p e t t and H e n d r ic k s o n h av e b o th
c a r r i e d o u t r e a c t i o n s o f p h o s p h o ra n e s o f th e ty p e (1 29 )
w i th d i m e t h y l a c e t y l e n e d i c a r b o x y l a t e .
R3?= CHR"
( 129 )
—5 ""
H e n d r ic k so n fo und t h a t p h e n a c y l i d e n e t r i p h e n y l -
p h o sp h o ran e (129 ; R = Ph; R = — CO — Ph) gave an a d d u c t , f o r
which he s u g g e s te d th e s t r u c t u r e (1 3 0 ) .
Ph.
PRa
-COOCHa
COOCHa
( 130)
He a l s o showed t h a t on p y r o l y s i s th e a d d u c t gave an
a c e t y l e n e o f s t r u c t u r e ( I 3 l ) .
P h - C = C - C = CH/ \
GHa0 0 0 COOCHa
(1 3 1 )
The a c e t y l e n e s y n t h e s i s o f T r i p p e t t and Gough i n v o lv i n g
p h o s p h o b e ta in e s o f th e ty p e (132) h a s a l r e a d y b e en d i s c u s s e d
(S ee p . 3o ) . A p p l i c a t i o n o f th e s e r e s u l t s to H e n d r i c k s o n 's
( 132)
compound s u g g e s t a s t r u c t u r e (133),® which w ould p re s u m a b ly
-5 7 -
g iv e th e a c e t y l e n e (131) on p y r o l y s i s .
COOMe
COOMePhgP . C = G H - CI
- 0 (133)
T h is a d d u c t would be fo rm ed by a p a th a n a lo g o u s to ( a )127
above . T r i p p e t t o b t a i n e d s i m i l a r a d d u c ts w i th o t h e r
p h o sp h o ra n e s and d i m e t h y l a c e t y l e n e d i c a r b o x y l a t e and
s u g g e s te d a n a lo g o u s s t r u c t u r e s f o r them a l l . I n a l a t e r13 0
p u b l i c a t i o n H e n d r ic k so n a l s o s u g g e s t s t h e s e s t r u c t u r e s .
P a th s ( a ) , (b ) and ( c ) above have a l l b e e n
o b s e rv e d , b u t th e f o u r t h s u g g e s t e d p a t h , w hich can o n ly work
f o r th e a c e ty l e n e c a s e , h ad n o t . However, H uebner andl 3 l 1 3 2 ,133 ,134:
Dorfm ann, and a number o f o t h e r w o rk e rs ,
have shown t h a t t h e a d d i t i o n o f b o th a c t i v a t e d and
n o n - a c t i v a t e d a c e t y l e n e s to en am in es in v o lv e d a c y c lo b u te n e
i n t e r m e d i a t e ( 1 3 4 ) , w hich c o u ld even be i s o l a t e d i n c e r t a i n
c a s e s . T h is c a n be r e a d i l y s e e n to be a n a lo g o u s t o th e
f o u r t h p o s s i b l e r e a c t i o n p a th i n th e p h o sp h o ra n e c a s e .
J COOR COOR‘COOR
-5 8 -
T h is r e a c t i o n h a s b e en u s e d t o expand R ing A134:
o f th e s t e r o i d a l n u c l e u s .
To i n c r e a s e t h e p o s s i b i l i t y o f th e f o u r t h r e a c t i o n
p a th th e o t h e r r e a c t i o n p a t h s w ere made im p o s s ib l e o r , a t
l e a s t , d i f f i c u l t .
The p o s s i b i l i t y o f p a th ( a ) was e a s i l y rem oved by
s u b s t i t u t i o n o f th e a -h y d ro g e n b y a l k y l i n th e p h o sp h o ra n e .
E l i m i n a t i o n o f p a t h (b ) was f a r more d i f f i c u l t , a l th o u g h 128
Bestm ann s u g g e s t s t h a t p a t h (b ) becom es l e s s l i k e l y
i f th e p h o sp h o ran e h a s e l e c t r o n w i th d ra w in g g ro u p s on t h e
a - c a r b o n a tom . F o r t u n a t e l y , p a th ( b ) ,w h i c h would l e a d t o
a c y c lo p ro p a n e d e r i v a t i v e , a p p e a r s u n im p o r ta n t i n th e
a c e t y l e n e c a s e . P a th ( c ) c a n n o t o p e r a t e b e c a u se no g ro u p
v/hich c an form a s t a b l e a n io n i s p r e s e n t .
T h ree p h o sp h o ra n e s were r e a c t e d w i th d im e th y l
a c e t y l e n e d i c a r b o x y l a t e , a —e th o x y c a rb o n y l e t h y l i d e n e t r i p h e n y l -
p h o sp h o ran e ( 1 3 5 ) , a - b e n z o y l e th y l i d e n e t r i p h e n y lp h o s p h o r a n e
( 136 ) and a - c y a n o e th y l id e n e t r ip & e n y lp h o s p h o r a n e (1 3 7 ) .
Me Me MeI I I
PhaP= G-COOEt PhaP= C - CO - Ph P haP = C -C N
( 135 ) ( 1 3 6 ) ( 137 )
I t was o r i g i n a l l y i n te n d e d t h a t th e m e th y l e s t e r
“59-
would be u s e d i n p l a c e o f ( 1 3 5 ) . However, a l th o u g h th e
phosphonium s a l t from m e th y l a -b ro m o p ro p io n a te and
t r ip h e n y lp h o s p h in e was r e a d i l y p r e p a r e d , a l l a t t e m p t s to
form th e p h o sp h o ran e from t h i s l e d to d e c a r b o x y l a t i o n and
th e f o r m a t io n o f th e e th y l t r ip h e n y lp h o s p h o n iu m s a l t . The
phosphonium s a l t o f t h e e t h y l e s t e r , h o w e v e r , r e a d i l y
form ed th e c o r r e s p o n d in g p h o sp h o ra n e on t r e a tm e n t w i th one
e q u i v a l e n t o f aqueous sodium h y d ro x id e a t 0°C . A p o s s i b l e
e x p la n a t i o n o f t h i s i n v o lv e s th e c a s e o f h y d r o l y s i s o f th e1 3 5 ,136 ,137
e s t e r g ro u p s . C o n s id e r a b le p r e v i o u s work h a s
d e m o n s tra te d th e i n s t a b i l i t y o f phosphonium s a l t s c o n t a i n i n g
a n a - c a r b o x y l a t e a n io n . I f t h i s a n io n i s p ro d u c e d , by th e
h y d r o l y s i s o f th e e s t e r g ro up b e in g f a s t e r t h a n th e f o r m a t io n
o f th e p h o sp h o ra n e , d e c a r b o x y l a t i o n w i l l r a p i d l y t a k e p l a c e .
T h is a p p e a r s to be th e c a s e w i th th e m e th y l e s t e r , w h i le th e
e t h y l e s t e r p re su m ab ly l o s e s an a - p r o t o n more r a p i d l y . These
r e s u l t s a r e i n ag reem en t w i th th e g e n e r a l r e a c t i v i t y o f e s t e r s
to w ard s h y d r o l y s i s .
The p h o sp h o ra n e s ( 1 3 5 ) , (1 3 6 ) and (137) a l l r e a c t e d
w i th d i m e t h y l a c e t y l e n e d i c a r b o x y l a t e t o g i v e , a f t e r c h ro m a to
g ra p h y , p a l e y e l lo w , c r y s t a l l i n e a d d u c t s .
The N.M.R. s p e c t r a o f t h e s e a d d u c t s were t a k e n .
—60*“
The compound from a - h e n z o 'y l e t h y l i d e n e t r i p h e n y l p h o s p h o r a n e
and th e a c e t y l e n e gave a sp e c tru m w hich c o u ld be e x p la in e d
on th e b a s i s o f compound (1 3 8 ; R= — CO —P h ) , w hich would
be th e e x p e c te d p ro d u c t from a r e a r r a n g e m e n t a n a lo g o u s t o
( 1 2 7 ) . A d o u b le t a t 7.^8'!^( J p = 3 c . p . s . ) due to th e
t e r m in a l m e th y l , a s i n g l e t a t 7 . 2 ^ due to one e s t e r m e th y l ,
and th e o t h e r e s t e r m e th y l a t 6 , 5 ^ ( a d i f f u s e s i n g l e t ) ,
c o u ld be d i s t i n g u i s h e d .
COOMe
PhaPI= c— - c = c
/COOMe ^
( 138)
However, when th e sp ec tru m o f th e a d d u c t from
a - c y a n o e th y l id e n e t r ip h e n y lp h o s p h o r a n e was s t u d i e d ^ i t
a p p e a re d t h a t a m ix tu r e o f two compounds v/as p r e s e n t . The
f i r s t , p r e s e n t i n 60 ^ , h ad a d o u b le t a t 8 . 0 ^ , J p = 3 c . p . s . ,
and two s i n g l e t s , one a t 6 .6 ^ and th e o t h e r a t 6 . 7 ^ . The
s e c o n d , p r e s e n t i n 3 0 ^ , h a d a s i m i l a r s p e c t ru m , b u t th e
d o u b le t was a t 8 . 3 ^ , J p = 4 c . p . s . , and th e two s i n g l e t s
a t 6 . 3 ^ and 6 .6 3 ^ r e s p e c t i v e l y . T h is c o u ld p o s s i b l y be
e x p la in e d by g e o m e t r i c a l i s o m e r i s o n . a c r o s s th e C —C d o u b le
bond i n (13 8 ; R = — CH), t h e d o u b le t s a t 8 . 0 ^ and 8 . 3 ^
—6 l—
b e in g due t o th e t e r m i n a l m e th y ls i n th e tv/o i so m e rs and
th e s i n g l e t s a t 6 , 6 ^ and 6 . 7 ^ , and 6 . 5 ^ and 6 . 65^ , t o
th e e s t e r m e th y l g ro u p s .
The c a s e o f th e a d d u c t from a - e t h o x y c a r b o n y l -
e t h y l i d e n e t r ip h e n y lp h o s p h o r a n e (1 3 8 ; R= — COOEt) a m ix tu r e
o f compounds a g a i n a p p e a re d to be p r e s e n t , a l t h o u g h one
p re d o m in a te d ( ^ 9 0 % ) . One iso m e r h ad a s i n g l e t a t 6 . 3T
due to th e two e s t e r m e th y l g r o u p s , w h i le t h i s was a t 6 . 6 T
i n th e o th e r i s o m e r . The t e r m i n a l m e th y l shov/ed a s a
d o u b l e t , a t 8 . l 0 ^ ( J p = ij. c . p . s . ) i n one i s o m e r , and a t
8 . 2 ^ ( J p = i+ c . p . s . ) i n th e o t h e r .
The p r o p o r t i o n s o f th e iso m e rs p r e s e n t i n each
c a se i s f u r t h e r e v id e n c e f o r g e o m e t r i c a l fo rm s b e in g
p r e s e n t . The p h e n a c y l c a s e (138 ; R = — COPh) was a p u re
compound, and w h i le t h e e s t e r p h o sp h o ran e a d d u c t (138 ;
R= — COOEt) was a 9 :1 m i x t u r e , th e n i t r i l e p h o sp h o ra n e a d d u c t
( 138 ; R = — CN) was a 3 : 2 m ix tu r e . As th e s i z e o f R d e c r e a s e s
i n t h i s o r d e r th e e f f e c t a p p e a r s t o be s t e r i c , and may be
due t o th e l a r g e p h o s p h o r u s - c o n ta in in g s u b s t i t u e n t a t th e
d o u b le bond a l lo w in g th e R g roup t o become c i s to i t i n th e
c a s e o f R = — CN, and t o a l e s s e r e x t e n t when R = — COOEt.
By r e p e a t e d r e c r y s t a l l i s a t i o n p u re sam p le s o f th e m a jo r
i so m er o f each a d d u c t were p r e p a r e d . However, when t h e s e
-62-
8am ples were t r e a t e d w i th p e r c h l o r i c a c i d , t h e N.M.R. s p e c t r a
o f th e s a l t s p ro d u ce d showed them a l s o to he m ix t u r e s .
Assum ing t h a t the a d d u c t s a r e of the form ( 1 3 8 ) , p r o t o n a t i o n
c o u ld t a k e p l a c e i n two w ays, a t th e a - c a r b o n , t o g iv e th e
p e r c h l o r a t e ( 1 3 9 ) , o r a t t h e ^ - c a r b o n , t o g iv e ( l 4 0 ) .COOMe
a p r o t o n a t i o n + | ^ 0 %
:OOMe 1 ' 'Rr + I /^ P h g P - C H - G :
PhaP= G - G = Q/ G i o r COOMe (13 9 )
^ , P h a ' t - G = G - C i r ^ ° X - p r o t o n a t i o n I
C lO r GOOMle (140)
T h ere a r e s e v e r a l r e c o r d e d exam ples o f e l e c t r o p h i l i c a t t a c k
a t th e ^ —c a rb o n i n a l l y ^ i c p h o s p h o ra n e s . Bestm ann h a s shown
t h a t t r e a tm e n t o f th e a l l y l i c p h o sp h o ran e ( l 4 l ) w i th23
c h lo r o c a rb a m a te s l e a d s to aQ - s u b s t i t u t e d p r o d u c t , a s d o es26
t r e a tm e n t w i th t r i t i a t e d w a te r .
TP h 3 P = C H - C H = CHg
(141) Cl-COOMe
G H = G H - G H o T
Phg f - GH = GH - GHg - GOOMa G1
T rea tm en t o f th e p e r c h l o r a t e m ix tu r e s w i th
aq u eo u s sodium h y d ro x id e gave back th e o r i g i n a l a d d u c t s .
—63-
h o w ev er , th e y a g a i n a p p e a re d t o he m ix tu r e s o f g e o m e t r i c a l
i s o m e r s , even th ough p u re sam p les were u se d i n th e p r e p a r a t i o n
o f th e s a l t s .
I n th e hope o f o b t a i n i n g f u r t h e r i n f o r m a t i o n from
N.M.R. s p e c t r a a t t e m p t s were made to h y d ro g e n a te th e
p e r c h l o r a t e s o f th e a d d u c t s . Adam 's c a t a l y s t , p a l l a d iu m on
c h a r c o a l , p la t in u m on c h a r c o a l , and Raney N ic k e l were a l l
t r i e d u n d e r v a r i o u s c o n d i t i o n s w i th a s i n g u l a r l a c k o f
s u c c e s s . A c o n t r o l e x p e r im e n t showed t h a t i t v/as im p o s s ib le
t o h y d ro g e n a te c in n a m ic a c i d i n th e p r e s e n c e o f phosphonium
s a l t , p re su m ab ly b e c a u s e th e s a l t p o i s o n e d th e c a t a l y s t i nL3 8
some way. S in c e o u r w ork , H e n d r ic k so n h a s su c c e e d e d i n
h y d r o g e n a t in g th e a d d u c t s th e m s e lv e s .
A t te m p ts to m e th y la te th e a d d u c t s u s in g m e th y l
io d id e were u n s u c c e s s f u l , th e a d d u c t b e in g r e o b t a i n e d i n
h ig h y i e l d .
A lth o u g h th e a d d u c ts were o n ly r e o b t a i n e d i n lov/
y i e l d from a t t e m p te d a c i d h y d r o l y s i s r e a c t i o n s u s in g
c o n c e n t r a t e d h y d r o c h l o r i c a c i d , no o t h e r c r y s t a l l i n e p r o d u c t
was i s o l a t e d . However, t r e a tm e n t o f the m o th e r l i q u o r s o f
t h e s e r e a c t i o n s w i th d i l u t e a l k a l i gave a f u r t h e r s m a l l
amount o f a d d u c t , show ing t h a t some c o n v e r s io n o f t h e a d d u c t
t o i t s s a l t had t a k e n p l a c e .
-6 4 -
The a d d u c ts r e a c t e d r e a d i l y w i th brom ine to g iv e
compounds which c o u ld n o t be s a t i s f a c t o r i l y p u r i f i e d .
D e g r a d a t io n o f t h e a d d u c t s was fo u n d to be d i f f i c u l t ,
p ro lo n g e d r e f l u x i n g w i th c o n c e n t r a t e d a l k a l i b e in g n e c e s s a r y .
The a d d u c t from a - b e n z o y le t h y l i d e n e t r ip h e n y lp h o s p h o r a n e
( 138 ; R= — COPh) was d e g ra d e d b o th b e c a u se i t was e a s i e s t
to p u r i f y and c o n ta in e d a p h e n a c y l g ro u p , w hich i s s t a b l e
to h y d r o l y s i s . The p r o d u c t s were t r ip h e n y lp h o s p h in e o x id e ,
i n h ig h y i e l d , a c r y s t a l l i n e a c i d i n v e r y low y i e l d and
t r a c e s o f p ro p io p h en o n e and a compound w hich h a d an
i n f r a r e d sp e c tru m s i m i l a r t o t h a t o f fu m a r ic a c i d .
The u l t r a v i o l e t sp e c tru m o f th e c r y s t a l l i n e a c i d
showed a d e f i n i t e s i m i l a r i t y to t h a t o f p - b e n z o y l a c r y l i c
a c i d ( 142 ) .
Ph - CO - CH = CH - GOOH
( 142)
The compound a n a ly s e d f o r CigHigOg and showed two
c a r b o n y l g ro u p s (one o f w hich a p p e a re d to be due to a
c a r b o x y l i c a c i d ) , a d o u b le bond and a m o n o - s u b s t i t u t e d
benzene r i n g , i n th e i n f r a r e d . On h y d r o g e n a t io n th e
compound to o k up 1 .7 m o les o f h y d ro g en p e r m ole and
t i t r a t i o n w i th a l k a l i gave an e q u i v a l e n t w e ig h t o f 1 9 4 - 10.
-6 5 -
The m ass sp e c tru m o f th e a c i d showed what
a p p e a re d to be a m ass p e a k a t m/e = 193>, and s t r o n g p e a k s
a t m /e = 77 (p h e n y l ) and m/e = 105 (B e n z o y l ) ,
T h is e v id e n c e p o i n t s t o two p o s s i b l e s t r u c t u r e s
f o r th e a c i d , (143) and ( l 4 4 ) , one o f w h i c h , ( 1 4 4 ) , c o u ld
HOOC-CHg GO - Ph HOGG G Q -P h
>K ><H CHs CHa CHg
(143) (144)
have b e en fo rm ed by d e c a r b o x y l a t i o n o f th e o r i g i n a l
h y d r o l y s i s p r o d u c t o f th e a d d u c t .
A t te m p ts to c a r r y o u t th e N.M.R. sp ec tru m o f
th e sodium s a l t o f t h i s a c i d i n d e u te r iu m ox id e l e d to
d e u te r iu m e x c h a n g e , a l t h o u g h th e i n d i v i d u a l o r t h o , m eta
and p a r a p r o t o n s o f t h e m o n o s u b s t i t u t e d benzene r i n g
c o u ld be p ic k e d o u t . The a c i d was n o t v e r y s o l u b l e i n
d e u te r o c h lo r o f o r m , b u t s p e c t r a were o b ta in e d a t 50°G.
The q u a l i t y was p o o r , b u t a d o u b l e t , due to a m e th y l g ro u p ,
a t 8 . 3 ^ ( j ^ = 7 c . p . s . ) and a m u l t i p l e t , p r o b a b ly due t o a
— GHg —, a t 6 . l Y c o u ld be d i s t i n g u i s h e d . The p e ak a t 6 . . l O ^ i n t e g r a t i n g f o r two h y d ro g en s and th e s p l i t t i n g o f 7 c . p . s .
o f th e m e th y l g ro u p s u g g e s t t h a t s t r u c t u r e ( l 4 3 ) i s th e
-66—
c o r r e c t o n e .
S in c e t h i s work h a s b e en c a r r i e d ou t a
c o n s i d e r a b l e amount h a s b e en p u b l i s h e d on a d d u c ts o f1 3 8 ,139
t h i s t y p e , a d d u c t s o f im in o p h o sp h o ra n e s w i th
a c e t y l e n e d i c a r b o x y l a t e (w hich a p p e a r t o be a n a lo g o u s )1 4 1
and a d d u c t s o f p h o sp h o ra n e s w i th b e n zy n e . The e v id e n c e
from t h i s work i s t h a t p h o sp h o ra n e s w i th o u t a - h y d r o g e n s ,
and p h o s p h o im in e s , r e a c t w i th d i m e t h y l a c e t y l e n e d i c a r b o x y l a t e
v i a a f o u r membered t r a n s i t i o n s t a t e l e a d i n g to p h o sp h o ra n e s
o f th e ty p e ( l4 3 ) *
PhgPz: C,\ j j 3
•COOMe
COOMePhoP
COOMe
COOMe'4
Pha,P= C - C = CR^R*
COOMe
(145 )
Z b i r a l s u g g e s t s t h a t th e f i r s t s t a g e i n th e r e a c t i o n o f
p h o s p h o ra n e s w i th benzyne i s i d e n t i c a l w i th t h a t a b o v e ,
a t t a c k o f th e y l i d c a r b a n io n a t one end o f t h e benzyne
-6 7 -
**t r i p l e " bond to g iv e th e b e t a i n e (1 4 6 ) . T h is c a r b a n io n
th e n a t t a c k s one of th e p h e n y l g ro u p s on th e p h o sp h o ru s
t o g iv e t h e p h o sp h in e ( 1 4 7 ) .
P h a P = C H - P h +- II P h a l CH Ph
PhcP — GH Ph
( 146)
(147)
T h is r e a r r a n g e m e n t i s a n a lo g o u s to t h a t i n th e r e a c t i o n o f
t r i p h e n y lp h o s p h in e w i t h d im e th y l a c e t y l e n e d i c a r b o x y l a t e
(See p . 5 3 ) , where th e i n i t i a l l y fo rm ed 1 , 5 - d i p o l e c a n
r e a r r a n g e to g iv e t l 4 8 ) by th e a t t a c k o f th e c a r b a n i o n a s
a p h e n y l g ro u p .
-68-
PhgP +
'GOOMe
‘COOMe
COOMe^GOOMe
GOOMeGCOMe
GOOMe
G ^m eGOOMe
GOOMe
GOOMe
OOMe
GOOMeGOOMe
( 148)
McEwen h a s s t u d i e d th e r e a c t i o n o f b e n z o n i t r i l e w i th
p h o s p h o ra n e s . I n th e c a s e o f b e n z y l id e n e t r i p h e n y lp h o s p h o r a n e
th e p r o d u c t s . C a f t e r a l k a l i n e h y d r o l y s i s ) were d e o x y b e n z o in
and p h o sp h in e o x id e . The f o l lo w in g r e a c t i o n p a t h h a s b e en
s u g g e s t e d .
-6 9 -
Ph3P = C H -P h + PhCN
D i l u t ePhaPO
[ P h - CH= G - PlQ NaOH' HHgI
P h - C H a - C - P h
Ph —r
PhaP CH
: IH T Z Z C
Ph —J
PhaP:
HN-
I t seemed p o s s i b l e t h a t by r e p l a c i n g th e a -h y d ro g e n atom
i n th e o r i g i n a l p h o sp h o ra n e by an a l k y l g ro u p , W iich
c a n n o t e a s i l y m i g r a t e , a r e a r r a n g e m e n t a n a lo g o u s t o t h a t
above m ig h t be f o r c e d to ta k e p l a c e to g iv e ( 150 ) .
PhaP=C R a + PhCH
PhaP = H - G = a\
(150)
phoP— c;"
TPhR
R
( 149)
—70—
However, when i s o p r o p y l id e n e t r i p h e n y l p h o s p h o r a n e was
r e a c t e d w i th h e n z o n i t r i l e , a l th o u g h a v ig o r o u s r e a c t i o n
to o k p l a c e , no c r y s t a l l i n e compounds c o u ld be i s o l a t e d .
A l k a l i n e h y d r o l y s i s o f th e r e a c t i o n m ix tu re gave
t r ip h e n y lp h o s p h in e ox id e and i s o p r o p y lp h e n y l k e to n e .
T h is k e to n e c o u ld have b e e n fo rm ed by h y d r o l y s i s o f e i t h e r
th e i n t e r m e d i a t e ( l4 9 ) o r th e r e a r r a n g e d p r o d u c t ( 150 ) .
-7 1 -
E x p e r im e n ta l
A l l e x p e r im e n ts u s in g p h o s p h o ra n e s , and s i m i l a r
u n s t a b l e compounds, were c a r r i e d o u t u n d e r an o x y g e n - f r e e
n i t r o g e n a tm o s p h e re . A l l s o l v e n t s were d r i e d b e f o r e u s e .
M e l t in g p o i n t s were c o r r e c t e d .
A t te m p te d p r e p a r a t i o n o f g - M e th o x y c a rb o n y le th y l id e n e -
t r i p h e n y lp h o s p h o r a n e . - a - M e t h o x y c a r b o n y l e t h y l t r i p h e n y l -143
phosphonium i o d i d e ( 9 .5 g . ) was d i s s o l v e d i n e t h a n o l -
w a te r ( 1 :1 ) (80 m l . ) and one e q u i v a l e n t o f sodium h y d ro x id e
( IE ; 20 m l . ) added s lo w ly w i th s t i r r i n g . The s o l u t i o n
rem ained c l e a r and v/as e x t r a c t e d w i th c h lo r o fo r m . The
c h lo ro fo rm s o l u t i o n was d r i e d and e v a p o r a te d to g iv e
e th y l t r ip h e n y lp h o s p h o n iu m io d id e (5*8 g . ) , m .p . and m ixed
m .p . (from c h lo r o f o r m - e t h y l a c e t a t e ) l 6 6 - l 6 7 ° .
89P r e p a r a t i o n o f C y a n o m e th y le n e t r ip h e n y lp h o s p h o ra n e . - The
89phosphonium s a l t (15»7 g . ) v/as d i s s o l v e d i n w a te r (300 m l . )
and one e q u i v a l e n t o f aqueous sodium h y d ro x id e (IN ; 47 m l . )
v/as added s lo w ly a t 0° w i th s t i r r i n g . The s o l i d p r e c i p i t a t e
was f i l t e r e d and w ashed w i th w a te r u n t i l th e w a sh in g s were
n e u t r a l . Thorough d r y in g and r e c r y s t a l l i s a t i o n from e t h y l
-7 2 -
a c e t a t e gave th e p h o sp h o ra n e ( 1 0 .4 g . ) , m .p . (from89
e t h y l a c e t a t e ) 195-196° ( l i t . 1 9 5 -1 9 6 ° ) .
P r e p a r a t i o n o f a -C y a n o e th y l t r ip h e n y lp h o s p h o n iu m I o d i d e . -
C y a n o m e th y le n e t r ip h e n y lp h o s p h o ra n e ( 1 2 g . ) and m e th y l
i o d i d e (25 g . ) were h e a t e d t o g e t h e r , w i th o u t s o l v e n t , a t
1 0 0 ° f o r l6 h o u r s . The r e a c t i o n m ix tu r e was t r i t u r a t e d
w i th benzen e (5 x 50 m l . ) . The b e n z e n e - i n s o l u b l e o i l
c r y s t a l l i s e d from e t h a n o l - w a t e r (1 2 g . ) , m .p . (from
e t h a n o l - w a t e r ) 1 2 0 - 1 2 2 ° . [Pound: G, 5 4 .5 ; H , 4 . 3 ; G a le ,
f o r Ggj^HigNPI: C, 5 6 .8 0 ; H , 4 . 3 , G a le , f o r G g iH ig N P I . HgO:
G, 5 4 .6 ; H, 4 . 5 ^ ] .
P r e p a r a t i o n o f a - G y a n o e th y l id e n e t r ip h e n y lp h o s p h o r a n e . - The
phosphonium i o d i d e (7 g . ) was d i s s o l v e d i n c h lo ro fo rm (60 m l . )
and c o o le d to 0 ° . T h is s o l u t i o n was sh ak en i n a s e p a r a t o r y
f u n n e l w i th an i c e - c o l d s o l u t i o n o f sodium h y d ro x id e ( 0 . 2 5 g . )
i n w q te r (50 m l . ) f o r one m in u te . The c h lo ro fo rm l a y e r was
s e p a r a t e d , w ashed w i th w a te r ( 4 x 3 0 m l . ) , d r i e d and
e v a p o r a t e d t o g i v e th e p h o sp h o ra n e ( 4 . 1 g . ) , m .p . ( f ro m
e t h y l a c e t a t e - p e t r o l ) 173-174® [P ound : G, 7 6 . 6 , H, 5 .7 ;
N , 3 . 5 ^ , G a le , f o r GgiHigNP: C, 8 0 .0 ; H, 5 .7 6 ; N, 4 .45 /S ].
-7 3 -
P r e p a r a t i o n o f a -E th o x y c a r 'b o n y le th y l t r lp h e n y lp h o sp h .o n i 'u m69
Brom ide . - E t h y l a -h r o m o p r o p i o n a t e (5 2 g , ) and t r i p h e n y l
p h o sp h in e (75 g . ) were d i s s o l v e d i n benze n e (400 m l . ) and
r e f l u x e d t o g e t h e r f o r 7 h o u r s . The o i l which s e p a r a t e d
was d e c a n t e d o f f and t r i t u r a t e d w i t h e t h y l a c e t a t e t o g i v e
t h e phosphonium s a l t (89 g . ) m .p . ( f rom c h l o r o f o r m - e t h y l
a c e t a t e ) 199-201° ( l i t . 1 9 9 - 2 0 0 ° ) .
P r e p a r a t i o n o f a - E t h o x y c a r b o n y l e t h y l i d e n e t r i p h e n y l p h o s -69
p h o r a n e . — The phosphonium s a l t (22 g . ) was d i s s o l v e d i n
e t h a n o l - w a t e r ( 1 :1 , . 200 m l . ) and c o o l e d t o 0 ° . One
e q u i v a l e n t o f aqueous sodium h y d r o x id e ( IN ; 50 m l . ) v/as
s l o w l y added w i th s t i r r i n g . The o i l w h ich s e p a r a t e d
c r y s t a l l i s e d on t r i t u r a t i o n (13 g . ) , m .p . ( f ro m e t h y l
a c e t a t e ) 157-159° ( l i t . 1 5 6 - 1 5 7 ° ) .
P r e p a r a t i o n o f a - M e t h y l p h e n a c y l t r i p h e n y lp h o s p h o n i u m43
Brom ide . - a -B rom oprop iophenone (32 g . ) and t r i p h e n y l
p h o s p h in e (40 g . ) were r e f l u x e d t o g e t h e r i n b en zen e (200 m l . )
f o r l 6 h o u r s . The o i l which s e p a r a t e d c r y s t a l l i s e d (6 2 g . )
on t r i t u r a t i o n w i t h e t h y l a c e t a t e , m .p . and m ixed m .p .
( f rom c h l o r o f o r m - e t h y l a c e t a t e ) 2 4 2 -2 4 3 ° .
-7 4 -
43P r e p a r a t i o n of g - M e t h y l p h e n a c y l i d e n e t r i p h e n y l p h o s p h o r a n e . -
The phosphonium s a l t (25 g . ) was d i s s o l v e d i n e t h a n o l - w a t e r
( 1 : 1 ; 300 m l . ) . One e q u i v a l e n t o f aqueous sodium h y d r o x id e
( IN ; 53 m l . ) was ad ded s l o w l y w i t h s t i r r i n g . The p r e c i p i t a t e
v/as f i l t e r e d , washed w i t h w a te r and d r i e d (20 g . ) , m .p . and
m ixed m .p . ( f rom e t h y l a c e t a t e ) l 6 l - l 6 3 ° .
R e a c t i o n o f D i m e t h y l A c e t y l e n e d i c a r b o x y l a t e w i t h
< x - E t h o x y c a r b o n y l e t h y l i d e n e t r i p h e n y l p h o s p h o r a n e . - T h e
pho sp h o ran e (12 g . ) , i n e t h y l a c e t a t e (150 m l . ) , was added
t o a s o l u t i o n of t h e d i e s t e r (5 g . ) i n e t h y l a c e t a t e (50 m l . ) .
The deep r e d r e a c t i o n m ix t u r e was r e f l u x e d f o r 3 h o u r s .
E v a p o r a t i o n and c h ro m a to g ra p h y on Woelmu n e u t r a l a lu m in a
u s i n g benzene a s t h e e l u e n t , gave y e l l o w c r y s t a l s (5 g . )
m .p . [ f rom l i g h t p e t r o l e u m ( b . p . 1 0 0 -1 2 0 ° ) ] 137-138° (Pound:
G, 6 8 .9 0 ; H, 5*90; P , 6 . 3 0 ; C a l c , f o r a 1 : 1 a d d u c t
GggHsgPOg: G, 6 9 .0 ; H, 5*75; P , 6 . 1 5 ^ ) .
P r e p a r a t i o n o f th e P e r c h l o r a t e o f t h i s A d d u c t . - The a d d u c t
( 1 . 2 g . ) was d i s s o l v e d i n m e th a n o l (10 m l . ) and an aqueous
s o l u t i o n of p e r c h l o r i c a c i d {lOfo) added d ro p w ise u n t i l t h e
o r i g i n a l y e l lo w c o l o u r o f th e s o l u t i o n was d i s c h a r g e d .
-7 5 -
A d d i t i o n of w a t e r t o t u r b i d i t y gave c r y s t a l s ( 0 . 9 g # ) ,
m .p . ( m e th a n e 1 -w a te r ) 179-181° (Pound: 0 , 5 6 .0 ; H, 5*00; P ,
5 . 5 9 ; C a lc , f o r OggHgoClPOio: 0 , 57*60; H, 4*97; P , 5 * 1 5 ^ ) .
R e a c t i o n o f a - C y a n o e t h y l i d e n e t r i p h e n y l p h o s p h o r a n e w i t h
D im e th y l A c e t y l e n e d i c a r b o x y l a t e . - The p h o sp h o ra n e ( l l g . ) , i n
c h lo r o f o r m (120 m l . ) , was added t o a s o l u t i o n of t h e d i e s t e r
(5 g . ) i n c h lo r o f o r m (20 m l . ) . The r e a c t i o n m i x t u r e was
r e f l u x e d f o r 3 h o u r s . E v a p o r a t i o n and c h ro m a to g ra p h y on
V/oelm n e u t r a l a lu m i n a , u s i n g benzen e a s t h e e l u e n t , gave
y e l lo w c r y s t a l s (4 g . ) m .p . [ f rom c a r b o n t e t r a c h l o r i d e - l i g h t
p e t r o l e u m ( b . p . 6 0 - 8 0 ° ) ] 149-151° (Pound: C, 7 0 .8 0 ; H, 5*22;
P , 7 . 0 1 ; C a lc , f o r a 1 : 1 a d d u c t G27H24PNO4 : C, 7 0 . 9 ;
H, 5 .2 5 ; P , 6 . 7 8 ^ ) .
P r e p a r a t i o n o f th e P e r c h l o r a t e o f t h i s A d d u c t . - The a d d u c t
(2 g . ) was d i s s o l v e d i n m e th a n o l (10 m l . ) and an aqu eo us
s o l u t i o n o f p e r c h l o r i c a c i d (70^) was ad d ed dropv/ise u n t i l
t h e o r i g i n a l y e l lo w c o l o u r o f th e s o l u t i o n v/as d i s c h a r g e d .
A d d i t i o n o f w a te r t o t u r b i d i t y gave c r y s t a l s (,1.7 g . ) , m .p .
( f rom m e t h a n o l - w a t e r ) 184—185° (Pound: C, 5 7 .5 ; H, 4*39;
P , 5 *5 6 ; C a lc , f o r C2.7H25 CINPO8 : C, 58.1;: H, 4 . 4 8 ; P , 5 * 5 5 ^ ) .
R e a c t i o n o f a ’-^ M eth y lp h en a cy l ldene t r lph e n y lph o sp ho rane w i t h
D im e th y l A c e t y l e n e d i c a r b o x y l a t e . - The p h o sp h o ra n e (8 g . ) ,
i n e t h y l a c e t a t e (100 m l . ) , was a d d ed t o a s o l u t i o n of th e
d i e s t e r (3 g . ) i n e t h y l a c e t a t e (30 m l . ) . The r e a c t i o n
m i x t u r e was r e f l u x e d f o r 3 h o u r s . E v a p o r a t i o n and
ch ro m a to g ra p h y on Y/oelm n e u t r a l a lu m i n a , u s i n g benzene
a s t h e e l u e n t , gave y e l lo w c r y s t a l s ( 8 . 4 g . ) m .p .
(f rom c a r b o n t e t r a c h l o r i d e - p e t r o l ) 191-192° (Pound: G, 7 3 .7 9 ;
H, 5 . 0 8 ; C a lc , f o r a 1 : 1 a d d u c t CasHggOgP: C, 7 3 .8 0 ; H, 5 .4 0 /0*
P r e p a r a t i o n o f t h e P e r c h l o r a t e of t h i s A d d u c t . — The a d d u c t
(1 g . ) was d i s s o l v e d i n m e t h a n o l (8 m l . ) and an aqueous
s o l u t i o n o f p e r c h l o r i c a c i d (70^) was added d ro p w ise u n t i l
th e s o l u t i o n became c o l o u r l e s s . A d d i t i o n o f w a t e r gave
c r y s t a l s ( 0 . 6 g . ) m .p . ( f rom m e t h a n o l —w a t e r ) 2 0 2 -2 0 4 ° .
A t te m p te d M é t h y l a t i o n o f t h e A dduc t from a - C y a n o e t h y l i d e n e -
t r l p h e n y l p h o s p h o r a n e and D im e th y l A c e t y l e n e d i c a r b o x y l a t e . -
( a ) The a d d u c t ( 0 . 8 g . ) , i n b e n ze n e (10 m l . ) , an d m e t h y l
i o d i d e (5 m l . ) were r e f l u x e d t o g e t h e r f o r 20 h o u r s .
E v a p o r a t i o n gave th e a d d u c t ( 0 . 6 g . ) . (b ) The a d d u c t ( 0 . 5 g . ) ,
and m e th y l i o d i d e (4 m l . ) , were h e a t e d t o g e t h e r on a s team
b a t h f o r 2 d a y s . E v a p o r a t i o n gave th e a d d u c t ( 0 . 3 g . )
-7 7 -
S i m i l a r r e s u l t s w e r e o b t a i n e d f r o m a n a l o g o u s
e x p e r i m e n t s w i t h t h e a d d u c t s f r o m a - m e t h y l p h e n a c y l i d e n e -
t r i p h e n y l p h o s p h o r a n e a n d a - e t h o x y c a r b o n y l e t h y l i d e n e -
t r i p h e n y l p h o s p h o r a n e .
R e a c t i o n o f t h e A d d u c t f r o m a - M e t h y l p h e n a c y l i d e n e t r i p h e n y l -
p h o s p h o r a n e a n d D i n s t h y l A c e t y l e n e d i c a r b o x y l a t e w i t h
H y d r o c h l o r i c A c i d . - T h e a d d u c t ( 1 g . . ) a n d c o n c e n t r a t e d
h y d r o c h l o r i c a c i d ( 2 m l . ) w e r e h e a t e d i n a s t e a m b a t h f o r
12 h o u r s . W a t e r ( 5 m l . ) w a s a d d e d a n d t h e s o l u t i o n f i l t e r e d .
E x t r a c t i o n o f t h i s s o l u t i o n w i t h e t h y l a c e t a t e g a v e a s m a l l
a m o u n t o f o i l . A d d i t i o n o f a q u e o u s s o d i u m h y d r o x i d e s o l u t i o n
( ^ . ) t o t h e a q u e o u s e x t r a c t u n t i l a l k a l i n e g a v e t h e o r i g i n a l
a d d u c t ( O . l g . ) , m . p . a n d m i x e d m . p . 1 9 1 - 1 9 2 °
S i m i l a r e x p e r i m e n t s v / i t h o t h e r a d d u c t s g a v e
a n a l o g o u s r e s u l t s .
R e a c t i o n s o f t h e A d d u c t s w i t h B r o m i n e . — A l l t h e a d d u c t s
r e a c t e d w i t h b r o m i n e . A t y p i c a l e x p e r i m e n t w a s :
t h e a d d u c t ( 0 . 8 g . . ) , i n b e n z e n e ( 1 0 m l . ) , w a s s l o w l y a d d e d
t o a s o l u t i o n o f b r o m i n e ( 0 . 2 8 g . ) i n b e n z e n e ( 5 m l . ) a n d
t h e m i x t u r e w a r m e d f o r 5 m i n u t e s . T h e o i l w h i c h s e p a r a t e d
-7 8 -
v/as t r i t u r a t e d w i t h e t h y l a c e t a t e t o g iv e a s o l i d v/hich
c o u l d n o t he s a t i s f a c t o r i l y p u r i f i e d .
A l k a l i n e H y d r o l y s i s o f t h e A dduc t from a - M e t h y l p h e n a c y l i d e n e -
t r i p h e n y l p h o s p h o r a n e and D im e th y l A c e t y l e n e d i c a r b o x y l a t e . - The
a d d u c t (2 g . ) , i n m e th a n o l (25 m l . ) , v/as ad ded t o a s o l u t i o n
o f sodium h y d r o x i d e (2 g . ) i n w a t e r (10 m l . ) . The s o l u t i o n
was r e f l u x e d f o r 60 h o u r s , c o o l e d and w a te r (30 m l . ) add ed .
The s o l i d v/as f i l t e r e d o f f ( 0 . 8 g . ) m .p . and mixed m .p .
157- 158° , w i t h an i n f r a r e d sp ec t ru m i d e n t i c a l w i t h t h a t o f
t r i p h e n y l p h o s p h i n e o x i d e . The f i l t r a t e v/as e x t r a c t e d w i t h
e t h e r (3 x 20 m l . ) , and t h e e t h e r e x t r a c t on g . l . c . (6 m. a p ie z o n L column a t 220°) showed p ro p io p h e n o n e (H^o).
E v a p o r a t i o n of th e e t h e r e x t r a c t gave a s m a l l q u a n t i t y o f
o i l (10 mg.) which h a d A 5 * 9 8 ^ . The a l k a l i n e e x t r a c t
was t h e n made a c i d t o Congo Red and th e r e s u l t i n g s u s p e n s i o n
e x t r a c t e d w i t h e t h e r ( 4 x 30 m l . ) . The e t h e r s o l u t i o n was
d r i e d (MgSO*) and e v a p o r a t e d t o g iv e a n o i l . The o i l
c r y s t a l l i s e d from m e t h a n o l - w a t e r (38 mg.) m .p . I 4 l - 1 4 2 ° ,
Xfflax 5 . 8 8 , 5 . 9 8 , 8 . 0 , 8 . 2 5 , 13 . 2 5 , 14 . 6/ 1 . (Found : C, 7 0 .5 1 ;
H, 6 .0 2 ; C a lc , f o r CisHigOg: C, 7 0 .6 0 ; H, 5 . 8 8 ^ ) .
-7 9 -
H y d r o g e n a t io n o f A c id from H y d r o l y s i s o f P h e n a c y l A d d u c t . -
The a c i d (7 m g . ) , i n e t h a n o l (,3 m l . ) was h y d r o g e n a t e d u s i n g
p a l l a d i u m on c h a r c o a l (3 mg.) a s c a t a l y s t . The u p ta k e
a f t e r 10 m i n u t e s was 1 . 2 m l . o f h y d ro g en . T h e o r e t i c a l
u p t a k e f o r one mole o f h y d ro g e n p e r m ole , 0 . 7 0 ml.
D e t e r m i n a t i o n o f t h e E q u i v a l e n t W eight o f th e A c i d i c
H y d r o l y s i s P r o d u c t by A l k a l i T i t r a t i o n . - The a c i d ( 5 . 9 mg.)
was d i s s o l v e d i n w a t e r (5 m l . ) and th e r e s u l t i n g s o l u t i o n
t i t r a t e d w i t h aqueous sodium h y d r o x i d e s o l u t i o n (N/lOO)
u s i n g p h e n o l p h t h a l e i n a s t h e i n d i c a t o r .
5 . 9 mg. of a c i d was e q u i v a l e n t t o 3 . 0 5 ml. o f
N / 100 sodium h y d r o x id e s o l u t i o n , g i v i n g an e q u i v a l e n t
w e ig h t o f 194. T h i s t i t r a t i o n was r e p e a t e d u s i n g s i m i l a r
c o n d i t i o n s and t a b u l a t i n g th e p .H . o f th e s o l u t io n (See
T ab le l ) .
-8 0 -
T a b l e I
t r e ( m l . ) p . H . T i t r e ( m l . ) p . H .
0 .0 7 5 . 9 8 3 .1 0 7 .4 0
0 .5 0 3 . 8 8 3 .2 0 8 .4 0
1 .0 0 4 . 3 0 3 .5 0 9 .0 0
1 .50 4 .6 0 4 . 0 0 9 .5 0
2 .0 0 4 .8 6 4 .5 0 9 .6 0
2 .5 0 5 .3 0 5 .0 0 9 .8 0
2 .90 6 .5 0 5 .5 0 9 .9 0
3 . 0 0 6 .7 0 6 .0 0 1 0 .0 5
R e a c t i o n o f I s o p r o p y l l d e n e t r i p h e n y l p h o s p h o r a n e w i t h
B e n z o n i t r l l e . - ( a ) I s o p r o p y l t r i p h e n y l p h o s p h o n i u m i o d i d e
( 15 g . ) , su sp en d e d i n e t h e r (200 m l . ) , v/as s t i r r e d and
LiBu i n e t h e r ( IN ; 35 m l . ) was a d d e d . The s o l u t i o n v/as
s t i r r e d f o r 1 h o u r a t room t e m p e r a t u r e . To t h i s s o l u t i o n
h e n z o n i t r i l e (10 m l . ) , i n e t h e r (20 m l . ) , was s l o w l y ad d ed ,
th e s o l u t i o n t u r n i n g from deep r e d t o b l a c k , and s t i r r i n g
c o n t i n u e d a t room t e m p e r a t u r e f o r I 6 h o u r s . The s o l u t i o n
v/as e v a p o r a t e d , d i s s o l v e d i n c h lo r o f o r m ( 15O m l . ) , washed
w i t h w a t e r (3 x 60 m l . ) and d r i e d . E v a p o r a t i o n gave an
o i l which c r y s t a l l i s e d on t r i t u r a t i o n w i th l i g h t p e t r o l e u m
—8 l—
( b . p . 40 - 60 °) t o g iv e t r i p h e n y l p h o s p h i n e o x ide ( 1 . 3 g . )
m .p . and mixed m .p . 1 5 7 -1 3 8 ° .
(b ) To a s o l u t i o n o f i s o p r o p y l i d e n e t r i p h e n y l p h o s p h o r a n e ,
from t h e phosphonium i o d i d e (15 g . ) and BuLi (IN; 35 m l ) ,
was s l o w l y added a s o l u t i o n o f h e n z o n i t r i l e (10 m l . ) i n
e t h e r (20 m l . ) . The r e s u l t i n g s o l u t i o n was s t i r r e d f o r
20 h o u r s a t room t e m p e r a t u r e . To t h i s s o l u t i o n m e th y l
i o d i d e (2 m l . ) , i n e t h e r (10 m l . ) , was added and th e
r e a c t i o n m i x t u r e r e f l u x e d f o r 4 h o u r s . The s o l u t i o n was
e v a p o r a t e d , d i s s o l v e d i n c h lo r o f o r m (200 m l . ) and washed
w i t h w a t e r (3 x 70 m l . ) . D ry ing (MgSO^) and e v a p o r a t i o n
gave an o i l v/hich c r y s t a l l i s e d on t r i t u r a t i o n w i t h e t h y l
a c e t a t e t o g i v e j fc -b u ty l t r ip h en y lp h o sp h o n iu m i o d i d e ( 2 . 3 g . )
m .p. and mixed m .p . ( f rom c h l o r o f o r m - e t h y l a c e t a t e )
204- 206° ( d ) .
( c ) To a s o l u t i o n of i s o p r o p y l i d e n e t r i p h e n y l p h o s p h o r a n e ,
from t h e phosphonium i o d i d e ( 8 . 6 g . ) and BuLi (IN; 20 m l . ) ,
was s l o w l y added a s o l u t i o n o f h e n z o n i t r i l e (8 m l . ) i n
e t h e r (20 m l . ) and th e r e s u l t i n g s o l u t i o n r e f l u x e d f o r
5 h o u r s . The e t h e r v/qs d i s t i l l e d o f f and sodium h y d r o x i d e
(10 g . ) i n m e t h a n o l - w a t e r ( 9 : 1 ; 100 m l . ) a d d ed . The s o l u t i o n
v/as r e f l u x e d f o r 1 h o u r , c o o l e d and e v a p o r a t e d . The
-82 -
r e s i d u e was e x t r a c t e d w i t h l i g h t p e t r o l e u m (4 0 -6 0 ° b . p . )
(5 X 50 m l . ) . The p e t r o l e x t r a c t was d r i e d (MgSO*) and
d i s t i l l e d t o g iv e t h r e e f r a c t i o n s ( a ) b . p . 1 0 0 - 1 2 0 ° ,
( b ) 122-144° and ( c ) 1 4 4 -1 8 0° . These f r a c t i o n s were
c h ro m a to g ra p h e d on p r e p a r a t i v e g . l . c . (20 f t . S i l i c o n
o i l column a t 1 8 0 ° ) . Three p u r e compounds were i s o l a t e d
( a ) d i m e t h y l - n - b u t y l c a r b i n o l ( 0 . 7 g . ) , (b ) i s o p r o p y l
p h e n y l k e to n e ( 0 . 7 g . ) and ( c ) n - b u t y l p h e n y l k e t o n e
( 1 . 4 g . ) a l l h a v in g i n f r a r e d s p e c t r a i d e n t i c a l t o t h a t
o f a u t h e n t i c s a m p le s .
-8 3 -
Some R e a c t i o n s o f P h o s p h o r u s - C o n t a i n i n g
B e t a i n e s i n W i t t i g R e a c t i o n s
T h e M e c h a n i s m o f t h e W i t t i g R e a c t i o n
A lth o u g h th e r e a c t i o n o f p h o s p h o r a n e s w i t h
a ld e h y d e s and k e to n e s v/as d i s c o v e r e d by S t a u d i n g e r and4 5 6
Meyer i n 1919, i t was n o t u n t i l 1953 t h a t W i t t i g
d e v e lo p e d i t i n t o a g e n e r a l method of o l e f i n s y n t h e s i s .
The scope and l i m i t a t i o n s o f th e s y n t h e s i s have43 ,59 ,6 0 ,91
b een d i s c u s s e d i n a l a r g e number o f p a p e r s and r e v i e w s
and r e c e n t l y more a t t e n t i o n h a s b e en d i r e c t e d t o t h e mechanism
of th e r e a c t i o n .
The s u g g e s t i o n t h a t t h e r e a c t i o n p r o c e e d e d v i a
an i n t e r m e d i a t e o f th e ty p e ( I 5 1 ) , o r i t s c o v a l e n t
e q u i v a l e n t ( 1 5 2 ) , was p u t f o r w a r d by W i t t i g i n h i s e a r l i e s t6 5 ,&44
p u b l i c a t i o n s .
PhoP— PhaP CR^r ® PhgP----- CR^R®■r\ ^ > - I or I0 = = C - r3 0 -----CR°R* 0 -----
R-0 CR®R'*
(151) (152)
He s u p p o r t e d t h i s t h e o r y w i t h t h e i s o l a t i o n of
2 - h y d r o x y -2 , 2 - d i p h e n y l e t h y 11 r iphenyIphosphon ium i o d i d e (153)
—84—
from th e r e a c t i o n m i x t u r e o f m e t h y l e n e t r i p h e n y I p h o s p h o r a n e145
and henzophenone a f t e r qu en ch in g w i t h h y d r i o d i c a c i d .
+■ + P h a P - ^ H g PhgP-----CHs PhgP----- GEg
_+ I — 10 = G P h g 0— GPhg HO— GPhg
(153)
The same typ e of b e t a i n e i n t e r m e d i a t e ( I 5 l ) was
a l s o p o s t u l a t e d i n th e r e a c t i o n o f t r i p h e n y l p h o s p h i n e w i t h6 5
s t y r e n e o x id e t o g i v e s t y r e n e and t r i p h e n y l p h o s p h i n e
o x id e .
P h a P / v c H g ^ PhaP--- G% PhaPO9 > o + 1
C H ^ " 0 ---CHPh GHg, = CHPhiPh
(151)
I f th e above f o r m u l a t i o n i s c o r r e c t we have tv/o
p o s s i b i l i t i e s f o r t h e r a t e d e t e r m i n i n g s t e p , b e t a i n e
f o r m a t i o n or b e t a i n e d e c o m p o s i t i o n .
I n b e t a i n e f o r m a t i o n , a ssum ing t h a t t h i s i n v o l v e s
n u c l e o p h i l i c a t t a c k of th e a - c a r b a n i o n o f t h e p h o sp h o ra n e on
th e c a r b o n y l g r o u p , th e r a t e w i l l depend on b o t h t h e
n u c l e o p h i l i c i t y o f th e cc-carbon and t h e r e a c t i v i t y d i s p l a y e d
—85—
to w a rd s n u c l e o p h i l e s by t h e c a r b o n y l g ro u p .
S u b s t i t u e n t s on th e a - c a r b o n which c a n d é l o c a l i s é
th e n e g a t i v e c h a rg e w i l l d e c r e a s e t h e r e a c t i v i t y o f t h e
p h o s p h o r a n e , w h i l e e l e c t r o n - d o n a t i n g s u b s t i t u e n t s on th e
p h o sp h o ru s w i l l i n c r e a s e t h e r e a c t i v i t y o f t h e p h o sp h o ra n e ,
by s t a b l i s i n g t h e d i p o l a r fo rm .
B e t a i n e d e c o m p o s i t i o n i s u s u a l l y assumed t o
p r o c e e d v i a a four-m em bered c y c l i c t r a n s i t i o n s t a t e , a l t h o u g h
t h e r e i s no r e a l e v id e n c e f o r t h i s . Any e l e c t r o n - d o n a t i n g
g ro up on th e p h o s p h o ru s w i l l d e c r e a s e i t s p o s i t i v e c h a r g e
and t h u s h i n d e r th e d e c o m p o s i t i o n , i n f a c t when th e p h o s p h o r u s
h a s t h r e e p -m e th o x y p h e n y l s u b s t i t u e n t s e l i m i n a t i o n w i l l n o t1 46
t a k e p l a c e and th e b e t a i n e i s s t a b l e . On t h e o t h e r hand
any s u b s t i t u e n t s on th e c a r b o n a toms of t h e b e t a i n e which
c an c o n j u g a t e w i t h t h e doub le bond t o be form ed w i l l h e l p t h e
e l i m i n a t i o n s t e p ; t h u s i n t e r m e d i a t e b e t a i n e s have n e v e r b e en
i s o l a t e d when s t a b l e p h o s p h o ra n e s o f t h e ty p e ( 1 5 4 ) have
b e e n u se d .
RgPz: C H - G O - R
(154)
The s t e r e o c h e m i s t r y , o f t h e o l e f i n s r e s u l t i n g from
a W i t t i g r e a c t i o n ^ i s d e te r m in e d by t h e s t e r e o c h e m i s t r y of
-8 6 -
t h e i n t e r m e d i a t e b e t a i n e s . I n t h e r e a c t i o n of t h e
p h o sp h o ra n e (155; H ) and t h e a ld e h y d e (156) v/e
have th e p o s s i b i l i t y o f tv/o s t e r e o i s o m e r i c b e t a i n e s
( 157 ) and ( 158 ) , which l e a d to c i s and t r a n s - o l e f i n s
r e s p e c t i v e l y a f t e r t h e e l i m i n a t i o n s t e p .
EsP= CHR + R GHO
( 155) (1 5 6 )
R3B
( 157)H
( 15 8 )
CIS
> = <
H
H R<t r a n s
I f th e b e t a i n e f o r m a t i o n s t e p i s s lo w , t h e n (158)
i s t h e p re d o m in a n t i so m er and th e o l e f i n fo rm ed i s m a i n l y
t r a n s , w h i l e a f a s t b e t a i n e fo rm in g s t e p p r o d u c e s a more
n e a r l y eq_ual m ix t u r e o f (157) and ( I 58 ) , and c o n s e q u e n t
amounts o f c i s and t r a n s - o l e f i n s .
-8 7 -
Th-us s t a b l e p h o s p h o r a n e s g i v e m a i n l y t r a n s
o l e f i n s when r e a c t e d w i t h a ld e h y d e s , w h i l e
p - n i t r o b e n z a l d e h y d e and p - m e t h o x y b e n z y l i d e n e t r i p h e n y l -
p h o s p h o r a n e , a r e a c t i v e a ld e h y d e and p h o s p h o r a n e , g i v e148
a m i x t u r e o f c i s and t r a n s - s t i l b e n e s . However,
a n i s a l d e h y d e and £ - n i t r o b e n z y l i d e n e t r i p h e n y I p h o s p h o r a n e
where b o t h t h e a ld e h y d e and p ho sp h o ra n e a r e d e a c t i v a t e d
by t h e s u b s t i t u e n t s , r e a c t s l o w ly t o g i v e m a i n l y th e148
t r a n s - s t i l b e n e .
R e a c t i o n s o f I n t e r m e d i a t e B e t a i n e s i n t h e W i t t i g R e a c t i o n
o t h e r t h a n O l e f i n F o r m a t i o n .
S in c e th e s u g g e s t i o n o f a b e t a i n e i n t e r m e d i a t e
l e a d i n g t o o l e f i n s i n th e W i t t i g r e a c t i o n , a number o f
o t h e r r e a c t i o n s o f t h e b e t a i n e h av e been p o s t u l a t e d .
R e s u l t s o b t a i n e d from a v a r i e t y o f W i t t i g r e a c t i o n s
h ad u s u a l l y b e e n r a t i o n a l i s e d by th e a s s u m p t io n t h a t th e
b e t a i n e - f o r m a t i o n s t e p v/as r e v e r s i b l e . However , i t was n o t
u n t i l 1963 t h a t e v id e n c e f o r t h i s was r e p o r t e d . S p e z i a l e 149
and H i s s i n g a l l o w e d e t h y l t r a n s - p h e n y I g l y c i d a t e and
t r i b u t y l p h o s p h i n e t o r e a c t , i n t h e p r e s e n c e o f m - c h l o r o b e n -
z a ld ehy d e , and o b t a i n e d b o t h e t h y l c in n a m a te and e t h y l
-88-
m -ch lo ro c in n a m a te * They assumed t h a t t h e b e t a i n e (159)
was th e i n t e r m e d i a t e , and t h a t i t c o u ld e l i m i n a t e p h o s p h in e
o x ide ( t h e no rm al W i t t i g p a t h ) t o g iv e c i n n a m a t e , o r
d i s s o c i a t e t o b e n z a ld e h y d e and p h o sp h o ran e which c o u ld t h e n
r e a c t w i t h t h e more r e a c t i v e m—chlorobenzaldehy de, B e t a in e
r e v e r s i b i l i t y h a s s i n c e b e en d e m o n s t r a t e d i n t h e c a s e o f15 0
u n s t a b l e p h o s p h o r a n e s .
BUqP 4 P h - C E - C H - C O O E t BUq P - CHGOOEt
(159)
BtioP = CHDOOEt + PhCHO
CHO
'VBUgPO
+
Ph - GH= GH~GOOEt
m - G 1 'G 6 % - GH= GH- GOOEt
+ BUgPO
The c o r r e s p o n d i n g r e a c t i o n s o f c i s and t r a n s -l 5 l
b u t - 2 - e n e e p o x id e s w i t h t r i b u t y l p h o s p h i n e do n o t a p p e a r
t o be c o m p l e t e l y s t e r e o s p e c i f i c , t h e t r a n s - e p o x i d e g i v e s
7 % c i s and 28/^ t r a n s - b u t e n e , and t h e c i s - e p o x i d e g i v e s
-8 9 -
81^ t r a n s and 19^ c i s - b u t e n e . Thus i t seems l i k e l y t h a t
b e t a i n e r e v e r s i b i l i t y i s t a k i n g p a r t t o g iv e t h e u n e x p e c t e d
s t e r e o i s o m e r .
A f u r t h e r example o f b e t a i n e r e v e r s i b i l i t y i s t o
be fo u n d i n t h e r e a c t i o n be tw een d i p h e n y I p h o s p h in e and 162
s t y r e n e o x i d e . The p r o d u c t s from t h i s r e a c t i o n a r e
e x t r e m e l y d e p e n d e n t upon t h e c o n d i t i o n s , b u t a t 140°, w i t h o u t
s o l v e n t , b e n z a ld e h y d e and m e t h y l d ip h e n y lp h o s p h i n e o x id e a r e
formed t o g e t h e r w i th o t h e r p r o d u c t s . P re su m a b ly t h e r e a c t i o n
p r o c e e d s v i a th e b e t a i n e ( l 6 o ) ( f u r t h e r e v id e n c e f o r t h i s
a s s u m p t io n i s g iv e n be low ; p .^^^ ) d i s s o c i a t i o n and
r e a r r a n g e m e n t g i v i n g b e n z a ld e h y d e and m e t h y l d i p h e n y l p h o s p h i n e ,
a- d k i - c iPhgPH + P h -C fH i-C H a -» P h a P jiC H a PhCHO
A HO^GHPhC v A,TTT1_ +
(160) PaaPjr\cHaHI
P h a P -G H q
I n t h i s c a s e i t was p o s s i b l e t o o b se rv e b e t a i n e r e v e r s i b i l i t y
b e c a u s e t h e p hosphorane fo rm ed i s r e a d i l y a b l e t o r e a r r a n g e
to th e p h o s p h i n e , t h u s rem oving any p o s s i b i l i t y o f r e f o r m i n g
th e b e t a i n e . A s i m i l a r r e a c t i o n t a k e s p l a c e i f t h e p r o d u c t
-9 0 -
from th e o p e n in g of t r a n s - s t i l b e n e o x id e w i t h sodium
d i p h e n y I p h o s p h id e , th e p h o sp h in e ( l 6 l ) , i s p r o t o n a t e d
w i t h e t h a n o l . The p r o d u c t s a r e b e n z a ld e h y d e and15 0
b e n z y l d i p h e n y l p h o s p h i n e .
A l t h o u g h i t i s p o s s i b l e t h a t t h i s r e a c t i o n p r o c e e d s
v i a an i n t e r m e d i a t e b e t a i n e s i m i l a r t o (l6o), a s t h e r e i s
an e q u i v a l e n t amount of b a se p r e s e n t , i n th e form o f
e t h o x i d e , once p r o t o n a t i o n of t h e oxygen h a s t a k e n p l a c e ,
p r o t o n a t i o n o f t h e p h o sp h o ru s would seem u n l i k e l y . An
a l t e r n a t i v e e x p l a n a t i o n i s t h a t t h e p - h y d r o x y p h o s p h in e
( 16 2 ) u n d e rg o e s a b a se c a t a l y s e d r e v e r s e a l d o l r e a c t i o n .
Phi^E. y E
P h a P P h » — iÇw 9 " " ^ P h EtOH
* L - = ^
( 1 6 1 )
P h a P - CHPh- C(OH)HPh ( 1 6 2 )
Etc
PhgPCHgPh + PhCHO
—91*”
A t h o r o u g h d i s c u s s i o n o f b e t a i n e r e v e r s i b i l i t y150
i s g i v e n i n r e f e r e n c e
A l t h o u g h r e v e r s i b l e b e t a i n e f o r m a t i o n m u s t b e
i n v o k e d i n r e a c t i o n s l i k e t h a t o f d i p h e n y l p h o s p h i n e w i t h
s t y r e n e o x i d e , w h e r e t h i s r e v e r s i b i l i t y i s u s e d t o e x p l a i n
b e t a i n e i n t e r c o n v e r s i o n t h e r e i s a p o s s i b i l i t y o f a f u r t h e r
e x p l a n a t i o n . T h e r e c o u l d b e d i r e c t i n t e r c o n v e r s i o n o f o n e
s t e r e o i s o m e r i c b e t a i n e t o t h e o t h e r w i t h o u t d i s s o c i a t i o n60
t o a l d e h y d e a n d p h o s p h o r a n e .
T h e tv/o i s o m e r i c b e t a i n e s , w h i c h c a n b e p r o d u c e d
b y t h e r e a c t i o n o f a p h o s p h o r a n e a n d a n a l d e h y d e , a r e
i n t e r e o n v e r t a b l e v i a t h e p h o s p h o r a n e ( 1 6 3 ) , f o r m e d b y t h e
r e m o v a l o f a p r o t o n f r o m t h e a —c a r b o n o f t h e i s o m e r i c
b e t a i n e s . O b v i o u s l y t h i s p r o t o n w i l l b e m o s t r e a d i l y r e m o v e d
w h e n i s a n a c t i v a t i n g g r o u p ; t h u s d i r e c t i n t e r c o n v e r s i o n
i s m o s t l i k e l y t o b e f o u n d i n W i t t i g r e a c t i o n s i n v o l v i n g
s t a b l e p h o s p h o r a n e s .
-9 2 -
RgPr: GHR^ + R®GHO
As a l l th e s t e p s shown may he o p e r a t i n g a t any g i v e n t ime
i t i s n o t u s u a l l y p o s s i b l e t o d i s t i n g u i s h be tw een them.15 0
However, T r i p p e t t h a s shown t h a t i n the sy s tem
i n c l u d i n g th e b e t a i n e ( I 6 5 ) d i r e c t i n t e r c o n v e r s i o n i s
r e l a t i v e l y u n i m p o r t a n t . When t h i s b e t a i n e was p r o d u c e d
from i t s c o r r e s p o n d i n g phosphonium i o d i d e Cl6i-|.) i n t h e
p r e s e n c e of an e x c e s s o f m - c h l o r o b e n z a l d e h y d e , 49^ o f
c i s and 9*9^ o f t r a n s - s t i l b e n e was form ed. The amount o f
t r a n s - s t i l b e n e was r e d u c e d t o hffo by f u r t h e r i n c r e a s i n g th e
e x c e s s o f m - c h l o r o b e n z a l d e h y d e .
-H
HO- Ph
(164)
-9 3 -
MePhgP. Base 0(
Ph
- n / X Ph
!H0
c i s - s t i l b e n e
c i s and t r a n s -MePhgP = GHPh m - c h l o r o s t i l b e n e
+ PhCHO (166)
Under t h e s e c o n d i t i o n s b e t a i n e i n t e r c o n v e r s i o n v i a
b e t a i n e d i s s o c i a t i o n i s i m p o s s i b l e b e c a u s e th e b e n z y l i d e n e -
p h o sp h o ra n e ( l 6 6 ) w i l l be i r r e v e r s i b l y c a p t u r e d by t h e
m -c h lo r o b e n z a ld e h y d e t o g i v e m - c h l o r o s t i l b e n e s . Thus t h e
s m a l l p e r c e n t a g e o f t r a n s - s t i l b e n e fo rm ed c an o n ly come from
d i r e c t i n t e r c o n v e r s i o n o f the b e t a i n e s v i a a p h o s p h o ra n e of
t h e t y p e ( 1 6 3 ) .
A n o t h e r r e a c t i o n o f i n t e r m e d i a t e b e t a i n e s h a s b e en163
d e s c r i b e d by Hands and M e rc e r . When p - h y d r o x y e t h y l t r i -
pheny lphosphon ium s a l t s ( 16? ) were t r e a t e d w i t h sodium
e t h o x i d e , i n e t h a n o l , p - e t h o x y e t h y l d i p h e n y l p h o s p h i n e ox ide
( 169 ) and b enzen e were fo rm ed . A s i m i l a r r e a c t i o n u s i n g
-9 4 -
aqueous p o t a s s i u m h y d r o x i d e gave p - h y d r o x y e t h y l d i p h e n y l -
p h o s p h in e o x i d e . Hands s u g g e s t e d t h a t t h e s e r e a c t i o n s i n v o l v e
a t t a c k by a l k o x i d e on t h e p - c a r b o n of th e b e t a i n e ( l 6 8 ) , t h e
f o r m a t i o n of a p h osp h o ru s oxygen bond and the e x p u l s i o n o f a
p h e n y l g ro u p a s i t s a n i o n , which t a k e s up a p r o t o n from t h e
s o l v e n t .
+ X“ ^ P h0
EtO~ V CHa V + Pit"
HOOEt CHs.
^OEt(167) ( 168 ) (169)
However, c o n s i d e r a t i o n o f th e a l c o h o l y s i s of164
phosphonium s a l t s makes t h i s mechanism a p p e a r u n l i k e l y .
Under c o n d i t i o n s o f a l c o h o l y s i s i t i s s u g g e s t e d t h a t th e
f i v e v a l e n t p h o s p h o r u s i n t e r m e d i a t e (170) i s fo rm ed
i n i t i a l l y , by a t t a c k o f a l k o x i d e on p h o s p h o r u s . F u r t h e r
a t t a c k o f a l k o x i d e on t h i s l e a d s t o th e f o r m a t i o n o f an
e t h e r and p h o s p h in e o x id e by d i s p l a c e m e n t o f t h e a n i o n (R^)~ .
-9 5 -
R2R^
^ R
(170)
A l c o h o l y s i s , how ever , w i l l o n ly t a k e p l a c e when R = b e n z y l
o r s u b s t i t u t e d b e n z y l , n o t when R^ = p h e n y l . I f we w r i t e
( l 6 8 ) a s (171) i t i s r e a d i l y s e e n t h a t th e mechanism
s u g g e s t e d by Hands i s a n a lo g o u s t o a l c o h o l y s i s *
?>Ph
PiLjP CHja
— CHcfla 1. OEt
(171)
There a p p e a r s t o be no v a l i d r e a s o n why a p h e n y l
g ro u p s h o u ld l e a v e i n t h i s c a s e when i t w i l l n o t i n n o fm a l
a l c o h o l y s i s .
A p o s s i b l e a l t e r n a t i v e t o t h i s mechanism i s t h e
r em o v a l o f a p r o t o n from th e a - c a r b o n atom i n th e b e t a i n e
(168) by a l k o x i d e , f o l l o w e d by t h e e l e c t r o n s h i f t s shown
-9 6 -
( 1 7 2 ) t o g i v e a v i n y l p h o s p h i n e o x i d e , w h i c h c a n r e a d i l y
a d d e t h a n o l t o g i v e H a n d s ’ p r o d u c t *
J^PhM 0-P h g R \ O E t
+ P h
( 172 )
2
EtOHV
P h . "
2
CHgOEt
I n t h e r e a c t i o n w i t h a q u e o u s p o t a s s i u m h y d r o x i d e i t i s
p o s s i b l e t h a t s i m p l e h y d r o l y s i s o f t h e p h o s p h o n i u m s a l t
i s t a k i n g p l a c e .
A f u r t h e r e x a m p l e o f t h i s t y p e c a n b e f o u n d i n t h e
r e a c t i o n o f d i p h e n y l p h o s p h i n e w i t h s t y r e n e o x i d e . T h e
d i p h o s p h i n e d i o x i d e (175) i s one o f s e v e r a l p r o d u c t s
i s o l a t e d a n d c o u l d b e f o r m e d b y t h e a d d i t i o n o f157 ,16 8
d i p h e n y l p h o s p h i n e o x i d e , o r i t s a n i o n , t o t h e
v i n y l p h o s p h i n e ( 1 7 4 ) , w h i c h i n t u r n may b e f o r m e d b y
—97—
p r o t o n a t i o n on oxygen o f t h e b e t a i n e (173) and s u b s e q u e n t
l o s s o f w a t e r , w i th o r w i t h o u t l o s s o f a p r o t o n from t h e
p h o s p h o r u s . S u b s e q u e n t a i r o x i d a t i o n g i v e s t h e p r o d u c t
( 1 7 5 ) .
PhaPH+
P l i - c m - CHa,
0II
PhaP^CHa
H.CH^ P h g P / ^ P h
(175)
9PhgP^
(1 7 3 )
PhgP,0II
: ’V al / C H
P h a P ^ ^Ph
Pha,P^CHaŒI
HO^ Ph
PhgP,'CH
IIOHN Ph
(174)
-9 8 -
Abnormal R e a c t i o n s o f t h e B e t a i n e s R3 P —CH^ GH(0)R
165W i t t i g h a s shown t h a t h e n z y l i d e n e t r i p h e n y l -
p h o sp h o ran e w i t h b e n z a ld e h y d e i n e t h e r g i v e s > 80^ o f
s t i l b e n e . The e q u i v a l e n t r e a c t i o n u s i n g sodium e t h o x i d e
i n e t h a n o l a s t h e b a se to p ro d u c e t h e p h o sp h o ra n e g i v e s
>96^ y i e l d o f s t i l b e n e s . However, m e t h y l t r i p h e n y l p h o s -
phonium h a l i d e s i n a l c o h o l i c - a l k o x i d e g iv e o n l y p o o r y i e l d s
o f o l e f i n s a n d , u n l i k e t h e b e n z y l s a l t s , do n o t u n d e rg o164
a l c o h o l y s i s . O b v io u s ly r e a c t i o n s o t h e r t h a n a l c o h o l y s i s
must be s u c c e s s f u l l y com pe t ing w i t h o l e f i n f o r m a t i o n i n
t h i s c a s e .
M e th y l t r ip h e n y lp h o s p h o n iu m b ro m id e , o r i o d i d e ,
on s t a n d i n g a t room t e m p e r a t u r e , w i t h b e n z a ld e h y d e i n
e t h a n o l i c sodium e t h o x i d e , formed s t y r e n e (l]yb) and a
h i g h l y c r y s t a l l i n e , i n s o l u b l e compound. T h i s v/as shown
t o be 1 , 2 - d i p h e n y l e t h y l d i p h e n y l p h o s p h i n e o x id e ( 1 7 6 ; R = P h ) .
F u s i o n o f t h i s compound w i t h a l k a l i gave a h i g h y i e l d o f166
s t i l b e n e and n o t 1 , 2 - d i p h e n y l e th a n e a s p r e v i o u s l y r e p o r t e d .
Compound (176), i s p r e s u m a b ly formed from t h e b e t a i n e (177)
by s i m u l t a n e o u s m i g r a t i o n of a p h e n y l g rou p from p h o s p h o r u s
to a - c a r b o n and of h y d r o g e n from gl t o t h e 0 - c a r b o n .
-9 9 -
4- OEtPhaP-C H a , Phg.P = CHg ^ Ph%P-GHj-H
O^CHR (177)
0 \kP h g P - CliPli.CHgR (176)
R ep lacem en t o f b e n z a ld e h y d e by s u b s t i t u t e d
b e n z a ld e h y d e s gave th e c o r r e s p o n d i n g p h o s p h in e o x id e s
( 176 ; R = m - c h l o r o p h e n y l , ^ - t o l y l , p i p e r o n y l , m - n i t r o p h e n y l )
whose s t r u c t u r e s were d e t e r m i n e d b o th by f u s i o n w i t h a l k a l i ,
and i d e n t i f i c a t i o n of th e r e s u l t i n g s t i l b e n e s , and by
s y n t h e s i s from b e n z y l h a l i d e s and m e t a l l a t e d b e n z y l d i p h e n y l -
p h o sp h in e o x id e .
As th e b e t a i n e (177; R = Ph) i s t h e e x p e c t e d
i n t e r m e d i a t e i n t h e r e a c t i o n o f t r i p h e n y l p h o s p l i i n e w i t h
s t y r e n e ox ide i t would seem r e a s o n a b l e t h a t th e p h o s p h i n e
o x id e ( 176 ; R= Ph) would be th e m a jo r p r o d u c t , a l t h o u g h6 5
W i t t i g and Haag have r e p o r t e d t h a t t h i s r e a c t i o n i n t h e
a b s e n c e o f s o l v e n t g i v e s s t y r e n e (50^) and t r i p h e n y l p h o s p h i n e
o x id e (86$^). However, when th e r e a c t i o n was c a r r i e d o u t
i n r e f l u x i n g e t h a n o l t h e r e a r r a n g e d o x id e (176; R = Ph) was
-1 0 0 -
forraed i n h i g h y i e l d .
T h i s l e d u s to b e l i e v e t h a t t h e r e a c t i o n was
h i g h l y d ep en d e n t on s o l v e n t , and f u r t h e r work showed t h i s
t o be t r u e . A l th o u g h r e a c t i o n i n d i - n - b u t y l e t h e r gave
t h e r e a r r a n g e d o x id e (176; R = B h ) i n somewhat r e d u c e d
y i e l d , r e a c t i o n i n benzene was e x t r e m e l y slow t o g i v e
s t y r e n e ( 36^ ) and t r i p h e n y l p h o s p h i n e o x id e ( 4 0 ^ ) , a f t e r
a w eek ,an d no t r a c e o f t h e r e a r r a n g e d o x id e ( 1 7 6 ) . Even
i n m e th a n o l t h e y i e l d o f th e o x id e (176) v/as r e d u c e d and
t h a t o f s t y r e n e c o n s e q u e n t l y i n c r e a s e d .
The m i g r a t o r y a p t i t u d e s of s u b s t i t u t e d p h e n y l
g ro u p s i n t h e above r e a r r a n g e m e n t were i n v e s t i g a t e d u s i n g+ —
b o th t h e r e a c t i o n s of t h e i o d i d e s MePhgPG6H.g3C.. I w i t h
b e n z a ld e h y d e s i n e t h a n o l i c sodium e t h o x i d e , and t h e r e a c t i o n s
o f th e p h o s p h i n e s P h g P G ^ w i t h s t y r e n e o x id e i n r e f l u x i n g
e t h a n o l . I n a l l r e a c t i o n s t h e o r d e r o f m i g r a t i o n was
m - c h l o r o p h e n y l ^ p h e n y l ^ p - a n i s y l , t h a t g ro u p m i g r a t i n g w h ich
i s t h e more s t a b l e a s t h e a n i o n . T h e r e f o r e , i t a p p e a r s
t h a t th e m i g r a t i n g g r o u p , w i t h i t s b o n d in g e l e c t r o n s , i s
b e in g ’’p u s h e d ” from t h e p h o s p h o r u s , t h e e l e c t r o n s h i f t
( I ; fo r m u la 177) b e in g i n advance o f t h e o t h e r s and th e
d r i v i n g f o r c e f o r t h e r e a c t i o n b e in g th e f o r m a t i o n o f t h e
ÿ — 0 bond. T h i s i s a n a lo g o u s t o th e b e n z i l - b e n z i l i c a c i d
-101-
r e a r r a n g e m e n t , which i n v o l v e s a t t a c k o f h y d r o x i d e a n i o n
on one c a r b o n y l o f b e n z i l , f o l lo w e d by m i g r a t i o n o f a
p h e n y l a s an a n io n from t h i s c a rb o n t o t h e o t h e r
c a r b o n y l c a r b o n .
OH ^ C - C0 - ? 0 0—
■ - H O - C - C ^ -» H O - G - G ,
The s e a r c h f o r r e a r r a n g e m e n t s of t h i s ty p e i n s l i g h t l y
d i f f e r e n t sy s te m s was g r e e t e d w i t h v a r y i n g s u c c e s s . When
p r o p i o n a l d é h y d e was t r e a t e d w i t h m e t h y l t r i p h e n y l p h o s p h o n i u m
i o d i d e i n e t h a n o l i c sodium e t h o x i d e , no o l e f i n o r r e a r r a n g e d
o x id e was fo rm ed . T h i s i s p re s u m a b ly due t o n e i t h e r o f
t h e s e r e a c t i o n s b e in g a b l e t o compete w i t h b a se c a t a l y s e d
p o l y m e r i s a t i o n o f th e a ld e h y d e . E t h y l t r i p h e n y l p h o s p h o n i u m
i o d i d e w i th b e n z a ld e h y d e i n e t h a n o l i c sodium e t h o x i d e gave
h i g h y i e l d s o f 0 - m e t h y l s t y r e n e , and e v en h i g h e r y i e l d s i n
m e t h a n o l i c sodium m e th o x id e , no r e a r r a n g e d o x id e b e i n g
d e t e c t e d .
The r e a c t i o n of d i p h e n y l p h o s p h i n e w i t h s t y r e n e o x id e
was f a r more p r o f i t a b l e . Here i t was p o s s i b l e t o o b s e r v e ,
d e p e n d in g upon t h e c o n d i t i o n s u s e d , t h e m a j o r i t y o f t h e
—102—
r e a c t i o n o f b e t a i n e s . W i th o u t s o l v e n t a t 120° th e p r o d u c t s
were ( 3 - p h e n y le th y ld ip h e n y lp h o s p h in e o x id e (178) ( 2 5 ^ ) ,
p r e s u m a b ly form ed by a r e a r r a n g e m e n t ( a ) , a n a lo g o u s t o
t h a t o f th e b e t a i n e (177) to g i v e t h e o x id e ( 1 7 6 ) , b u t
i n v o l v i n g th e m i g r a t i o n o f h y d r i d e r a t h e r t h a n p h e n y l
a n i o n , t o g e t h e r w i t h b e n z a ld e h y d e (2lj^o) and m e t h y l d i p h e n y l -
p h o s p h in e ( i s o l a t e d a s t h e o x id e ) (3 i#^) , t h e s e l a s t two
p r e s u m a b ly b e in g fo rm ed by d i s s o c i a t i o n (b ) o f t h e
i n t e r m e d i a t e b e t a i n e ( 1 7 9 ) . V/hen th e r e a c t i o n was c a r r i e d
o u t i n r e f l u x i n g e t h a n o l t h e p r o d u c t s were s t y r e n e (6CÇo),
p r o b a b l y r e s u l t i n g from a c o n v e n t i o n a l W i t t i g e l i m i n a t i o n
( c ) from t h e b e t a i n e ( 1 7 9 ) , b e n z a ld e h y d e and m e t h y l d ip h e n y l -
p h o s p h in e (f rom b e t a i n e d i s s o c i a t i o n ) and t h e d i p h o s p h i n e
d i o x i d e ( l 8 0 ) , t h e p o s s i b l e mode o f f o r m a t i o n o f which h a s
a l r e a d y b e en d i s c u s s e d ( p . 9 7 ) .
0I I
PhgP -G H g-G H gPh
HPhg P = CHs -> PhgPGHg
PhgPH + Ph-GH-GHa
(178)
(a
(179) ^ PhGH= GHs
\PhsP—CiHs— carphPhgP = 0 (1 8 0 )
—103—
A u t h e n t i c d i o x i d e ( l 8 0 ) was s y n t h e s i s e d by
t h e t h e r m a l r e a r r a n g e m e n t o f t h e p h o s p h i n i t e ( l 8 l ) o b t a i n e d
from c h l o r o d i p h e n y l p h o s p h i n e an d 2 - h y d r o x y - 2 - p h e n y l e t h y l -
d i p h e n y l p h o s p h i n e o x id e ( l 8 2 ) .
0 0 II , , p y ^ I)
PhgPCl + PhaP-CH s-CH CO H )Ph ----- » P h g P ^
(1S2) (181)CHPh
P h g P - 0 ^
H e a t 120°
° »Ph^P
^GHs0 I (180)
CHPhPhgP-^
A number o f o t h e r e p o x id e s were r e a c t e d w i t h
t r i - and d i p h e n y l p h o s p h i n e . I t was found t h a t a l l t h e
r e a c t i o n s r e q u i r e d f a r more v i g o r o u s c o n d i t i o n s t h a n th o s e
o f s t y r e n e o x id e and p h o s p h i n e s , m a in ly s e a l e d t u b e s and
h i g h t e m p e r a t u r e s . T h i s i s a l i t t l e s u r p r i s i n g a s a s e a r c h
o f t h e l i t e r a t u r e showed no e v id e n c e of e x t r a r e a c t i v i t y
to w a rd s n u c l e o p h i l e s i n t h e c a s e o f s t y r e n e o x id e when
compared w i th o t h e r e p o x i d e s . 1 ,2 -E poxyhexane gave
h e x - l - e n e a s t h e m a jo r p r o d u c t on r e a c t i o n w i t h e i t h e r
-104-
d i - o r t r i p h e n y l p h o s p h i n e , p re su m ab ly by a no rm al W i t t i g
e l i m i n a t i o n . No b e t a i n e d i s s o c i a t i o n p r o d u c t s c o u ld be
d e t e c t e d i n e i t h e r c a s e . However, w i t h d i p h e n y l p h o s p h i n e ,
1 , 2 - epoxyhexane d i d g i v e a sm a l l y i e l d (ii/0 o f
h e x y ld i p h e n y l p h o s p h i n e o x id e ( l 8 3 ) p re s u m a b ly by a
mechanism s i m i l a r t o ( a ) above .
PhgPH + CHg - a i - ( CHa )s - CHg -» P h ^ ^C H jH
/ N gH - (CHg )a - CHa
I -1
P h g P - (CHg ) a - C H a
(183)
t r a n s - S t i l b e n e o x ide gave on ly p o o r y i e l d s of
s t i l b e n e , and p h o sp h in e o x i d e , when r e a c t e d v / i th o u t s o l v e n t
w i t h t r i p h e n y l p h o s p h i n e a t 180° f o r f o u r days and no o t h e r
i s o l a t a b l e p r o d u c t . T h i s was e q u a l l y t r u e o f c i s - s t i l b e n e156
o x id e .
The r e a c t i o n of 1 ,2 - e p o x y c y c lo h e x a n e w i t h
d ip h e n y l p h o s p h i n e gave c y c lo h e x e n e {6%) and c y c l o h e x y l -
d ip h e n y l p h o s p h i n e o x id e (30) a s t h e o n ly i s o l a t a b l e p r o d u c t s .
However, w i t h t r i p h e n y l p h o s p h i n e , o r m e t h y l d i p h e n y l p h o s p h i n e ,
—105""
a l t h o u g h th e y i e l d of o l e f i n was n o t im proved , th e
c o r r e s p o n d i n g c y c lo h ex e n y lp h p sp h o n iu m s a l t (185) was
fo rm ed . T h i s i s p r o b a b l y p r o d u c e d by e l i m i n a t i o n o f ”’0H
from th e i n t e r m e d i a t e b e t a i n e ( 1 8 4 ) .
R = Ph o r Me
OH
RPh.
PhgRP
(184)
T h i s may be a co n seq u e n ce of t h e h i g h e n e rg y
o f a t r a n s i t i o n s t a t e f o r o l e f i n f o r m a t i o n , i n v o l v i n g a
four -m em bered r i n g f u s e d d i e q u a t o r i a l l y t o a s i x membered
r i n g . Benzene (20 /0 was a l s o form ed i n t h e s e r e a c t i o n s ,
p r o b a b l y by d e c o m p o s i t i o n o f th e phosphonium h y d r o x id e
( 1 8 5 ) .
I n an a t t e m p t t o r a t i o n a l i s e t h e s e r e s u l t s
c y c l o o c t e n e ox ide was r e a c t e d w i t h t r i p h e n y l p h o s p h i n e .
The p ro b le m s o f a h i g h - e n e r g y t r a n s i t i o n s t a t e f o r o l e f i n
f o r m a t i o n sh o u ld n o t a r i s e i n t h i s c a s e b e c a u se t h e sys tem
w i l l c o n s i s t of a four -m em bered r i n g f u s e d t o an e i g h t -
membered. A l th o u g h th e r e a c t i o n r e q u i r e d even more
—106—
v i g o r o u s c o n d i t i o n s t h a n th e c y c lo h e x a n e c a s e , th e on ly
p r o d u c t s were p h o sp h in e o x id e and c y c l o o c t e n e (38/&), no
phosphonium s a l t b e in g fo rm ed .
I t c an be s e e n from t h i s d i s c u s s i o n t h a t i n t e r
m e d i a t e b e t a i n e s i n W i t t i g r e a c t i o n s can undergo a number of
r e a c t i o n s o t h e r t h a n e l i m i n a t i o n o f p h o sp h in e o x ide t o g iv e
o l e f i n s ; They may;
( a ) d i s s o c i a t e t o p h o sp h o ra n e and c a r b o n y l compound,
(b ) r e a r r a n g e t o p h o s p h in e o x ide by m i g r a t i o n of
p h e n y l from p h o s p h o ru s t o a - c a r b o n ,
( c ) s u f f e r f u r t h e r a t t a c k by n u c l e o p h i l e s t o g i v e
^ - s u b s t i t u t e d p h o s p h in e o x i d e s , and
(d ) e l i m i n a t e h y d r o x i d e t o g i v e v i n y l phosphonium
s a l t s .
E x p e r i m e n t a l
A l l e x p e r i m e n t s i n v o l v i n g p h o s p h o r a n e s and s i m i l a r
u n s t a b l e compounds were c o n d u c te d u n d e r a n o x y g e n - f r e e n i t r o g e n
a tm o sp h e re . A l l a r o m a t i c a ld e h y d e s were f r e s h l y d i s t i l l e d
u n d e r an o x y g e n - f r e e n i t r o g e n a tm o s p h e r e . A l l s o l v e n t s were
d r i e d b e f o r e u s e . M e l t i n g p o i n t s were c o r r e c t e d .
R e a c t i o n of M e th y l t r i p h e n y lp h o s p h o n iu m I o d i d e w i t h
B e n za ld eh yd e i n E t h a n o l i c Sodium E t h o x i d e . - A s o l u t i o n of
-107-
m e t h y l t r i p h e n y l p h o s p h o n i u m i o d i d e ( l 6 . 2 g . ) and b e n z a ld e h y d e
(4 .2 5 g . ) , i n e t h a n o l (60 m l . } , c o n t a i n i n g sodium (0*97 g * ) ,
v/as s e t a s i d e a t room t e m p e r a t u r e u n d e r o x y g e n - f r e e n i t r o g e n .
A f t e r 48 h r . , g . l . c . (2m. A p ie zo n column a t 130®) showed th e
p r e s e n c e o f s t y r e n e (1 0 ^ ) and b e n z a ld e h y d e (<5^0 , a n d f i l t r a
t i o n gave 1 , 2 - d i p h e n y l e t h y l d i p h e n y l p h o s p h i n e o x id e ( 6 8 ^ ) , m .p .
and m ixed m .p . ( f rom e t h a n o l ) 232-233® (Pound: G, 8 1 .3 ; H , 3 . 9 ;
P , 8 . 0 7 . C a l c , f o r CseHaaOP: G, 8 1 .6 ; H, 6 .0 2 ; P , 8 . 1 2 ^ ) .
The same e x p e r im e n t i n m e th a n o l gave s t y r e n e (26^) and o x id e
( 34^ ) . The ox ide (8 g . ) was f u s e d w i t h sodium h y d r o x i d e
(15 g . ) , t o which w a t e r (1 m l . ) h a d b e en ad d ed , f o r 2 h r . and
t h e c o o l e d m ix t u r e d i s s o l v e d i n w a t e r (200 m l . ) . E x t r a c t i o n
w i t h c h lo r o f o r m gave a s o l u t i o n which g . l . c . (2m. A p ie z o n
column a t 25O®) showed t o c o n t a i n c i s (40 ^ ) and t r a n s (8 ^ )
s t i l b e n e s . The aqu eo u s l a y e r g a v e , on a c i d i f i c a t i o n ,
d i p h e n y l p h o s p h i n i c a c i d ( 8 1 ^ ) , m .p . and mixed m .p . 192.-193°.
S i m i l a r e x p e r i m e n t s i n e t h a n o l u s i n g s u b s t i t u t e d
b e n z a ld e h y d e s gave th e f o l l o w i n g p h o sp h in e o x i d e s .
1 - P h e n y l - 2 - m - c h l o r o p h e n y l e t h y l d i p h e n y l p h o s p h i n e o x i d e , ( 4 8 ^ ) ,
m .p . and mixed m .p . ( f rom e t h a n o l ) 212-213®.
1 - P h e n y l - 2- 2 - t o l y l e t h y l d i p h e n y l p h o s p h i n e o x id e ( 4 C # ) , m .p .
an d mixed m .p . ( f ro m e t h a n o l ) 240-241®.
-108 -
l - P h e n y l - 2 - ( 3 * ,4 * - m e t l iy l e n e d lo x y p h e n y l ) e t h y l d i p h e n y l p h o s p h i n e
o x id e ( 38%), m .p . ( f rom e t h a n o l ) 204-203® (Pound: C, 7 6 . 6 ;
H, 3 . 8 ; P , 7 *1 3 . C27H23O3 P r e q u i r e s C, 7 6 . 2 ; H, 3 . 4 ; P , 7 . 3 ^ ) .
1 - P h e n y l - 2 -m -n i t r o p h e n y l e t h y l d i p h e n y l p h o s p h i n e o x ide ( lO o ) ,
m .p . ( f rom e t h a n o l ) 203-204® (Pound: C, 7 2 . 3 ; H, 3 . 2 ; P , 7 . 2 ;
N , 3 . 4 . C26H22NO3P r e q u i r e s C, 7 3 .0 ; H, 3 . 2 ; P , 7 .2 3 ;
N , 3 .3% ).
1 - P h e n y l - 2 -m- c h l o r o p h e n y l e t h y l d i p h e n y l p h o s p h i n e O x ide . -
E t h e r e a l b u t y l - l i t h i u m (13 m l . ) was added t o a s o l u t i o n
o f b e n z y l d ip h e n y l p h o s p h i n e o x id e ( 4 . 2 g . ) i n e t h e r (100 m l . )
and th e s o l u t i o n h e a t e d u n d e r r e f l u x f o r % h r . m -C h lo ro -
b e n z y l b romide (4 g . ) , i n e t h e r (40 m l . ) , was t h e n added and
t h e s o l u t i o n h e a t e d u n d e r r e f l u x f o r a f u r t h e r 2 h r . I t was
t h e n v/ashed w i t h w a t e r , d r i e d an d e v a p o r a t e d and th e r e s i d u e
c r y s t a l l i s e d from e t h a n o l t o g i v e th e p h o s p h in e o x id e ( 67%),
m .p . 212- 213®, (Pound: G, 7 4 . 3 ; H, 3 . 0 ; G l , 7 . 6 ; ? , 8 . 6 3 .
G26H22GIOP r e q u i r e s G, 7 4 . 7 ; H, 3 . 3 ; G l , 7 . 4 ; P , 8 . 3%),
P u s i o n w i t h sodium h y d r o x id e gave ( g . l . c . ) c i s ( 3 ^ ) and
t r a n s - 3 - c h l o r o s t i l b e n e (12%), and d i p h e n y l p h o s p h i n i c a c i d ( 7 ^ 0 <
A s i m i l a r e x p e r im e n t u s i n g 4 - m e t h y l b e n z y l b rom ide
gave 1—p h e n y l - 2 - p - to l y l e t h y l d i p h e n y l p h o s p h i n e o x ide ( 6 2 / 0 ,
m.p* ( f rom e t h a n o l ) 240-241® (Pound: G, 8 1 . 7 ; H, 6 . 3 ; P , 7 . 8 .
—109—
02 7^ 35GP r e q u i r e s C, 8 1 . 6 ; H, 6 . 3 ; P , 8 .0% ) . F u s i o n w i t h
sodium h y d r o x id e gave ( g . l . c . ) c i s (36%) and t r a n s - 4 - m e t h y l -
s t i l b e n e (7%), and d i p h e n y l p h o s p h i n i c a c i d (77%).
E x p e r im e n t s u s i n g m-C h l o r o p h e n y l d i p h e n y l p h o s p h i n e .
A s o l u t i o n o f c h l o r o d i p h e n y l p h o s p h i n e (35 g . ) i n e t h e r
(150 m l . ) was added s l o w l y t o t h e G r i g n a r d r e a g e n t from
m -c h lo r o io d o b e n z e n e (45 g . ) and magnesium (4*6 g. ) i n e t h e r
(200 m l . ) c o o le d t o 0®, and th e s o l u t i o n s t i r r e d a t room
t e m p e r a t u r e f o r 2 h r . 2 N - ^ y d r o c h l o r i c a c i d (250 m l . ) was
t h e n s l o w l y added f o l l o w e d by c h lo r o f o r m (200 m l . ) . The
o r g a n i c l a y e r was washed w i th w a t e r , d r i e d , and e v a p o r a t e d .
D i s t i l l a t i o n gave m - c h lo r o p h e n y l d i p h e n y l p h o s p h i n e (37 g . ) ,
b . p . 208-212®/2mm., which d i d n o t c r y s t a l l i s e and was
c h a r a c t e r i s e d a s th e m e t h i o d i d e . m .p . ( f rom c h l o r o f o r m - e t h y l
a c e t a t e ) 170-173® (Found: C, 5 2 . 0 ; H, 4 . 0 ; 0 1 , 7 . 9 5 ; P , 6 . 9 .
G igH i^C lIP r e q u i r e s G, 5 2 . 0 ; H, 3 . 9 ; 0 1 , 8 . 1 ; P , 7 .05% ).
m -G h lo ro p h en y lm e th y ld ip h en y lp h o sp h o n iu m i o d i d e
( 4 . 4 g . ) and b e n z a ld e h y d e ( 1 . 2 g . ) were added t o e t h a n o l
(50 m l . ) c o n t a i n i n g sodium ( 0 .2 5 g . ) and t h e s o l u t i o n s e t
a s i d e a t room t e m p e r a t u r e f o r 5 d a y s . W ater was t h e n added
t o t u r b i d i t y . G r y s t a l l i s a t i o n t h e n gave 1 - m - c h l o r o p h e n y l -
2 - p h e n y l e t h y l d i p h e n y l p h o s p h i n e o x id e ( 1 . 6 g . ) , m .p . and
-n o -
m ixed m .p . ( f rom aqueous e t h a n o l ) 193-194®. A s i m i l a r
e x p e r im e n t u s i n g m - c h lo r o b e n z a ld e h y d e ( 1 . 4 g . ) gave
1 , 2 - d i - m - c h l o r o p h e n y l e t h y l d i p h e n y l p h o s p h i n e o x id e ( 1 . 8 g . ) ,
m .p . and mixed m .p . ( f rom aqueous e t h a n o l ) 194-193®.
A s o l u t i o n o f m - c h l o r o p h e n y l d i p h e n y l p h o s p h i n e
( 2 .9 6 g . ) and s t y r e n e o x ide ( 1 . 2 g . ) i n e t h a n o l (25 m l . )
v/as h e a t e d u n d e r r e f l u x f o r 24 h r . , and w a t e r t h e n added t o
t u r b i d i t y . C r y s t a l l i s a t i o n gave l - m - c h l o r o p h e n y l - 2 - p h e n y l -
e t h y l d i p h e n y l p h o s p h i n e o x id e ( 3 . 1 g . ) , m .p . and m ixed m .p .
( f rom aqueous e t h a n o l ) 192-194®.
1 , 2 - D i -m -c h l o r o p h e n y l e t h y l d i p h e n y l p h o s p h i n e O x id e . -
A s o l u t i o n of m - c h l o r o b e n z y l b romide (8 g . ) i n benze n e (20 m l . )
was add ed s lo w ly t o a c o o l e d s o l u t i o n o f m e th y l d i p h e n y l -
p h o s p h i n i t e ( 7 . 8 g . ) i n benzene (20 m l . ) and th e r e s u l t i n g
s o l u t i o n h e a t e d u n d e r r e f l u x f o r 1 h r . A d d i t i o n of l i g h t
p e t r o l e u m ( b . p . 40 - 6O®) t h e n gave m-c h l o r o b e n z y l d i p h e n y l p h o s p h i n e
o x id e ( 7 .5 g . ) , m .p . 162 .5 -163 .3® (Found: G, 6 9 .6 2 ; H, 4*7 9 ;
P , 9 . 3 0 . GigHigClOP r e q u i r e s G, 6 9 . 8 0 ; H, 4 . 9 0 ; P , 9 .49% ).
E t h e r e a l I N - b u t y 1 - l i t h i u m (8 m l . ) was added to
m - c h l o r o b e n z y ld i p h e n y lp h o s p h in e o x id e ( 2 . 2 g . ) i n benzene
(100 m l . ) and th e s o l u t i o n h e a t e d u n d e r r e f l u x f o r 1 h r . and
t h e n c o o le d d u r i n g t h e a d d i t i o n o f m - c h l o r o b e n z y l bromide
-111-
(4 g . ) i n benzene (20 m l . ) . The r e s u l t i n g s o l u t i o n was
h e a t e d u n d e r r e f l u x f o r 1 h r . and t h e s o l v e n t t h e n removed
u n d e r r e d u c e d p r e s s u r e . A s o l u t i o n o f th e r e s i d u e i n
c h lo r o f o r m was washed w i t h w a t e r , d r i e d , and e v a p o r a t e d .
T h e r e s i d u e c r y s t a l l i s e d o n t r i t u r a t i o n w i t h l i g h t p e t r o l e u m
t o g i v e 1 , 2 - d i - m - c h l o r o p h e n y l e t h y l d i p h e n y l p h o s p h i n e o x i d e
( 2 . 3 g . ) , m . p . ( f r o m a q u e o u s e t h a n o l ) 194-193® ( F o u n d :
G, 6 9 .0 3 ; H, 4 . 6 ; G l , 1 5 .6 5 ; p , 7 . 0 . GggHgiGlgOP r e q u i r e s
G, 6 9 . 2 ; H, 4 . 6 5 ; G l , 1 5 .7 5 ; P , 6 .9 % ) . F u s i o n w i th s so d iu m
h y d r o x i d e gave ( g . l . c . ) c i s - 3 . 3 ^ - d i - c h l o r o s t i l b e n e ( 69%).
A s i m i l a r e x p e r i m e n t u s i n g b e n z y l b r o m i d e g a v e
l- f f l -c h l o r o p h e n y l - 2 - p h e n y l e t h y l d i p h e n y l p h o s p h i n e o x i d e ( 65%),
m . p . ( f r o m a q u e o u s e t h a n o l ) 192-193® ( F o u n d : G, 7 4 .8 5 ;
H, 5 .4 2 ; G l , 8 .4 5 ; P , 7 . 2 2 . GgsHggGlOP r e q u i r e s G , 7 4 .9 5 ;
H, 5 .2 8 ; G l , 8 . 5 ; P , 7 .22% ) . F u s i o n w i t h sodium h y d r o x id e
gave ( g . l . c . ) c i s - 3 - c h l o r o s t i l b e n e (73%).
E x p e r im e n t s w i t h p - M e t h o x y p h e n y ld ip h e n y lp h o s p h in e .
p -M e th o x y p h en y lm e th y ld ip h en y lp h o sp h o n iu m i o d i d e ( 4 . 3 4 g . )
and b e n z a ld é h y d e ( 1 . 2 g . ) were added t o e t h a n o l (20 m l . )
c o n t a i n i n g sodium ( 0 .2 5 g . ) and th e s o l u t i o n s e t a s i d e a t
room t e m p e r a t u r e f o r 4 d a y s . F i l t r a t i o n t h e n gave
I , 2 - d i p h e n y l e t h y l - p - m e t h o x y p h e n y l p h e n y l p h o s p h i n e o x i d e
( 1 .7 g . ) , m . p . ( f r o m e t h a n o l ) 185-186° ( F o u n d : Û, 7 8 .4 5 ;
-112-
H, 5 . 9 ; P , 7 . 5 . G27H25 O2P r e q u i r e s C , 7 8 .8 ; H, 6 . 1 ; P , 7 .5%).
P u s i o n w i t h sodium h y d r o x i d e gave ( g . l . c . ) c i s (40%) and
t r a n s - s t i l b e n e ( 8%) w i t h no t r a c e o f 4 - i n e t h o x y s t i l b e n e s .
A s i m i l a r e x p e r im e n t w i t h m - c h l o r o b e n z a ld e h y d e
( 1 .5 g . ) gave l - p h e n .v l - 2 -m -c h l o r o p h e n y le th y l - p - m e t h o x y p h e n y l
p h e n y lp h o s p h in e o x ide ( 1 .9 g . ) , m .p . ( f ro m aqueou s e t h a n o l )
165- 167® (Found: C, 72*7; H, 5*5; C l , 7*85; P , 6 . 9 .
C27H24CIO&P r e q u i r e s C , 7 2 . 5 ; H, 5*4; C l , 7*9; P , 6 .95% ).
F u s i o n w i th sodium h y d r o x i d e gave ( g . l . c . ) c i s (49^0 and a
t r a c e o f t r a n s - 5 - c h l o r o s t i l b e n e .
A s o l u t i o n o f p - m e th o x y p h e n y ld ip h e n y lp h o s p h in e ( 5 g . )
and s t y r e n e ox ide ( 2 . 1 m l . ) i n e t h a n o l (25 m l . ) was h e a t e d
u n d e r r e f l u x f o r 24 h r . and w a te r t h e n added t o t u r b i d i t y .
C r y s t a l l i s a t i o n gave 1 , 2 - d i p h e n y l e t h y l - £ - m e t h o x y p h e n y l p h e n y l
p h o s p h in e ox ide (3 g . ) , m .p . and m ixed m .p . ( f rom e t h a n o l )
185- 186*.
R e a c t i o n b e tw ee n T r i p h e n y l p h o s p h i n e and S t y r e n e
O xide . - A s o l u t i o n o f t r i p h e n y l p h o s p h i n e ( 7 . 5 g. ) and
s t y r e n e o x id e ( 3 . 5 g . ) i n e t h a n o l (50 m l . ) was h e a t e d u n d e r
r e f l u x f o r 24 h r . C r y s t a l l i s a t i o n t h e n gave 1 , 2 - d i p h e n y l -
e t h y l d i p h e n y l p h o s p h i n e o x id e ( 6 .3 g . ) m .p . and mixed m .p .
232- 233®. S t y r e n e (8%) was a l s o fo rm ed ( g . l . c . ) .
-113-
A s i m i l a r r e a c t i o n i n d i b u t y l e t h e r a t 120° f o r 20
h r . gave 1 , 2 - d i p h e n y l e t h y l d i p h e n y l p h o s p h i n e o x ide (40%) and
s t y r e n e (20%).
A s o l u t i o n o f t r i p h e n y l p h o s p h i n e (13 g . ) and
s t y r e n e o x id e (6 g . ) i n benzene (80 m l . ) was h e a t e d u n d e r
r e f l u x f o r 6 d a y s . S t y r e n e (32%) and unchanged s t y r e n e
o x id e (20%) were t h e n p r e s e n t ( g . l . c . ) . M ethyl i o d i d e
(10 m l . ) was t h e n ad d ed and th e s o l u t i o n h e a t e d u n d e r r e f l u x
f o r 1 h r . The s y r u p which s e p a r a t e d g a v e , on t r i t u r a t i o n
w i t h e t h y l a c e t a t e , m e th y l t r i p h e n y l p h o s p h o n i u m i o d i d e ( 7 . 7 g . ) ,
m .p . and mixed m .p . 1 8 9 -1 9 0 ° . The m o th e r l i q u o r s were
e v a p o r a t e d and th e r e s i d u e c h ro m a to g ra p h e d on a lu m in a .
E l u t i o n w i th benzen e gave t r i p h e n y l p h o s p h i n e o x id e (7 g . ) ,
m .p . and mixed m .p . 1 5 7 -1 5 8 ° .
R e a c t i o n o f E t h y l t r i p h e n y l p h o s p h o n i u m I o d i d e w i t h
B enza ldehy d e i n E t h a n o l i c Sodium E t h o x i d e . - A s o l u t i o n of
e t h y l t r i p h e n y l p h o s p h o n i u m i o d i d e ( 1 0 . 5 g . ) and b e n z a ld e h y d e
( 2 . 6 g . ) i n e t h a n o l (100 m l . ) c o n t a i n i n g sodium ( 0 . 5 1 g . )
was s e t a s i d e a t room t e m p e r a t u r e f o r 4 d ays ,w hen g . l . c .
showed t h e p r e s e n c e o f c i s (l6%) and t r a n s - 3 - m e t h y l s t y r e n e
(46%). The s o l u t i o n was e v a p o r a t e d and th e r e s i d u e , i n
c h lo r o f o r m , washed w i t h w a t e r , d r i e d , and th e s o l v e n t removed
u n d e r r e d u c e d p r e s s u r e . The r e s i d u e was e x t r a c t e d w i t h benzene
-1 1 4 -
l é a v i n g u n d i s s o l v e d e th y l t r i p h e n y l p h o s p h o n i u m i o d i d e ( 1 . 9 g . ) ,
m .p . and mixed m .p . 164-165®, and t h e e x t r a c t ch ro m a to g ra p h ed
on a lu m in a t o g i v e t r i p h e n y l p h o s p h i n e o x ide ( 2 . 4 9 g . ) , m.p .
and mixed m .p . 157-158®.
A s i m i l a r r e a c t i o n i n m e th a n o l gave c i s (26%) and
t r a n s - 3 - m e t h y l s t y r e n e (54%).
R e a c t i o n o f D ip h e n y lp h o s p h in e m t h S t y r e n e O x id e . -
( a ) w i t h o u t s o l v e n t . - D ip h e n y lp h o s p h in e ( 6 . 5 g . ) and
s t y r e n e ox ide ( 4 . 5 g . ) were h e a t e d t o g e t h e r u n d e r o x y g e n - f r e e
n i t r o g e n a t 140° f o r 12 h r . when g . l . c . showed th e p r e s e n c e
o f b e n z a ld e h y d e ( 2l{%) and s t y r e n e o x id e ( 20^b) . The r e a c t i o n
m i x t u r e , i n b e n z e n e , was c h ro m a to g ra p h e d on a lu m in a . E l u t i o n
w i t h b en zene gave 3 - p h e n y l e t h y l d i p h e n y l p h o s p h i n e o x id e ( 2 . 6 g . ) ,
m .p . an d mixed m .p . ( f rom l i g h t p e t r o l e u m ; b . p . 1 0 0 -1 2 0 ° )
103-105®; e l u t i o n w i t h b e n z e n e - e t h e r ( 1 : 1 ) gave m e t h y l d i p h e n y l
p h o s p h in e ox ide ( 2 . 4 g . ) , m .p . and m ix ed m.p. ( f rom l i g h t
p e t r o l e u m , b . p . 8 0 -1 0 0 ° ) 1 0 9 -1 10 ° .
(b ) i n e t h a n o l . - A s o l u t i o n o f d ip h e n y l p h o s p h i n e ( 8 . 1 g . )
and s t y r e n e o x id e (8 g . ) i n e t h a n o l (80 m l . ) was h e a t e d
u n d e r r e f l u x f o r 40 h r . when g . l . c . showed the p r e s e n c e o f
s t y r e n e (60%) and b e n z a ld e h y d e (13%). The s o l v e n t was
e v a p o r a t e d and th e r e s i d u e , i n b e n z e n e , c h ro m a to g ra p h e d on
a lu m in a . E l u t i o n w i t h benzen e gave l , 2 - d i ( d i p h e n y l p h o s p h i n y l ) -
1 -p h e n y l e th a n e (3 g . ) , m .p . and m ixed m .p . ( f rom e t h a n o l )
-115 -
283-2 84 ° ; e l u t i o n w i t h b e n z e n e - e t h e r ( l : l ) gave
m e t h y l d ip h e n y lp h o s p h i n e o x id e (2 g . ) , m .p . and mixed
m .p . 1 0 9 -1 1 0° .
1 ? 2 - D i ( d i p h e n y l p h o s p h i n y l ) - l - p h e n y l e t h a n e . -
C h lo r o d ip h e n y l p h o s p h i n e ( 2 . 2 g . ) was added t o a s o l u t i o n
o f 3 - h y d r o x y - 3 - p h e n y l e t h y l d i p h e n y l p h o s p h i n e o x id e ( 3 . 2 g . )
i n p y r i d i n e (10 m l . ) and th e s o l u t i o n h e a t e d u n d e r r e f l u x
f o r 3 hr* , , t h e n c o o l e d and p o u r e d i n t o w a t e r . The
p r e c i p i t a t e d s y r u p c r y s t a l l i s e d from aqueous e t h a n o l t o
g i v e 1 . 2 - d i ( d i p h e n y l p h o s p h i n y l ) - l - p h e n y l e t h a n e ( 3 . 4 g . )
m .p . 283-284° (P o u nd îC , 7 5 . 8 ; H, 5 . 4 ; P , 1 2 .0 .
r e q u i r e s C, 7 5 . 9 ; H, 5 . 5 ; P , 12 .2% ).
3 - P h e n y l e t h y l d i p h e n y l p h o s p h i n e O x id e . - A s o l u t i o n
o f d ip h e n y l p h o s p h i n e ( 3 . 4 g . ) i n t e t r a h y d r o f u r a n (30 m l . )
was h e a t e d u n d e r r e f l u x w i t h sodium w ire (6 g . ) f o r 2 h r .
The e x c e s s o f sodium was t h e n removed and 3 - b ro m o e th y lb e n z e n e
( 3 . 4 9 g . ) i n t e t r a h y d r o f u r a n (6 m l . ) ad d ed . The m ix t u r e was
h e a t e d u n d e r r e f l u x f o r 1 h r . , t h e s o l v e n t t h e n removed
u n d e r r e d u c e d p r e s s u r e and th e r e s i d u e , i n c h lo r o f o r m , washed
w i t h w a t e r and t h e n s t i r r e d a t room t e m p e r a t u r e f o r 10 m in u t e s
w i t h h y d ro g e n p e r o x i d e (6%). The s o l u t i o n was t h e n washed
w i t h w a t e r , d r i e d , and e v a p o r a t e d . The r e s i d u e c r y s t a l l i s e d
-116-
from l i g h t p e t r o l e u m t o g i v e P -ph en y l e t h y l d i p h e n y l p h o s p h i n e
o x id e (4 g . ) , m .p . 104-106° (Pound: 0 , 7 8 .3 ; H, 6 . 2 ; P , 1 0 .1 .
G20H1 9 OP r e q u i r e s G, 7 8 . 4 ; H, 6 . 2 ; P , 10. IJo).
R e a c t i o n s of 1 , 2 -Spoxyhexane w i t h P h o s p h i n e s . -
T r i p h e n y l p h o s p h i n e ( 3 . 2 4 g . ) and 1 ,2 -e p o x y h e x a n e ( 1 . 2 g . )
were h e a t e d t o g e t h e r i n a s e a l e d tub e a t 220° f o r 7 days
and th e p r o d u c t d i s s o l v e d i n e t h a n o l (23 m l . ) g . l . c . ( 50m.
c a p i l l a r y column c o a t e d w i t h p o l y p r o p y le n e g l y c o l , a t 4 0 °)
showed th e p r e s e n c e o f h e x - l - e n e ( 6 l%). The e t h a n o l was
e v a p o r a t e d and th e r e s i d u e c r y s t a l l i s e d from e t h y l a c e t a t e
t o g iv e t r i p h e n y l p h o s p h i n e o x id e ( 2 .4 g . ) , m .p . an d mixed
m .p . 157- 158° .
A s i m i l a r r e a c t i o n w i t h d ip h e n y l p h o s p h i n e gave
h e x - l - e n e (38%) and h e x y l d i p h e n y l p h o s p h i n e o x id e (4^o) h a v in g
an i n f r a r e d sp e c t ru m i d e n t i c a l w i t h t h a t o f an a u t h e n t i c
sam p le .
R e a c t i o n o f 1 , 2 -E pox y cyc loh ex an e w i t h P h o s p h i n e s . -
M e t h y ld ip h e n y lp h o s p h in e ( 4 g . ) and 1 ,2 - e p o x y c y c lo h e x a n e (2 g . )
were h e a t e d t o g e t h e r a t 120° f o r 30 h r . , c o o l e d , and t h e
p r o d u c t e x t r a c t e d v / i th e t h y l a c e t a t e (3 x 50 m l . ) . The
e x t r q c t was t r e a t e d w i t h m e th y l i o d i d e (5 m l . ) and s e t a s i d e
a t room t e m p e r a t u r e f o r I 6 h r . F i l t r a t i o n t h e n gave
d im e th y 1 d iphenyIphosphoniurn i o d i d e ( 2 . 3 g . ) , m .p . and m ixed
-117-
m .p. 256- 257° . The m o th e r l i q u o r v/as e v a p o r a t e d and t h e
r e s i d u e c r y s t a l l i s e d from l i g h t p e t r o l e u m t o g iv e
m e th y l d ip h e n y lp h o s p h i n e o x id e ( 1 . 3 g . ) , m .p . and mixed
m .p . 109- 110° .
The r e s i d u e from th e e x t r a c t i o n w i t h e t h y l a c e t a t e
was d i s s o l v e d i n c h lo r o f o r m and t h e s o l u t i o n washed (i+x)
w i t h s a t u r a t e d aqu eo u s p o t a s s iu m i o d i d e , d r i e d , and
e v a p o r a t e d . C r y s t a l l i s a t i o n of t h e r e s i d u e from c h l o r o f o r m /
e t h y l a c e t a t e gave c y c l o h e x - l - e n y l m e t h y l d ip h e n y lp h o s p h o n i u m
i o d i d e (.1 g . ) , m .p . and mixed m .p . 2 2 5 -2 2 6 ° , h a v in g an
i n f r a r e d spec t rum i d e n t i c a l w i th t h a t o f an a u t h e n t i c sam p le .
A s o l u t i o n o f t r i p h e n y l p h o s p h i n e ( 6 . 6 g . ) and
c y c lo h e x e n e ox ide ( 3 . 3 g . ) i n e t h a n o l (40 m l . ) was h e a t e d
u n d e r r e f l u x f o r 60 h r . G . l . c . (50 m. c a p i l l a r y column
c o a t e d w i t h p o l y p r o p y l e n e g l y c o l , a t 4 0 ° ) showed th e
p r e s e n c e o f c y c lo h e x e n e (50 ) and b en zene ( 2 ^ 6 ) . The
s o l u t i o n was e v a p o r a t e d an d th e r e s i d u e e x t r a c t e d w i th e t h y l
a c e t a t e (2 x 50 m l . ) . The e x t r a c t was h e a t e d u n d e r r e f l u x
vd t h m e th y l i o d i d e f o r % h r . t o g iv e m e t h y l t r i p h e n y l p h o s -
phonium i o d i d e ( l . 1 g . ) , m .p . and mixed m .p . 188- 189° .
- 1 1 8 -
The m o th e r l i q u o r , on e v a p o r a t i o n , g a v e t r i p h e n y l p h o s p h i n e
o x ide (3 g . ) , m .p . and m ixed m .p . ( f rom c h l o r o f o r m / l i g h t
p e t r o l e u m ) 13 7 -1 3 8° .
The r e s i d u e from th e e x t r a c t i o n w i t h e t h y l a c e t a t e
v/as d i s s o l v e d i n c h lo r o f o r m and t h e s o l u t i o n washed (4x)
w i t h s a t u r a t e d aqueous p o t a s s iu m i o d i d e , d r i e d , and
e v a p o r a t e d . The r e s i d u e c r y s t a l l i s e d from c h l o r o f o r m / e t h y l
a c e t a t e t o g iv e what i s p r o b a b l y c y c l o h e x - l - e n y l t r i p h e n y l -
phosphonium i o d i d e ( 0 . 4 g . ) , m .p . 2 2 8 - 2 3 3 ° . The compound
c o u ld n o t be s a t i s f a c t o r i l y p u r i f i e d . I t s n . m . r . sp e c t ru m
showed a d o u b l e t a t 3 .3 T ( J p g 22 c / s e c . ) e q u i v a l e n t t o one
p r o t o n .
C y c lo h e x - l - e n y l m e th y l d i p h e n y l p h o s p h o n i u m I o d i d e . -
G h l o r o d ip h e n y lp h o s p h in e (22 g . ) i n e t h e r (50 m l . ) v/as
s lo w ly added t o a s t i r r e d , c o o l e d , s o l u t i o n o f
e y e l o h e x - l - e n y 1 - l i t h i u m , p r e p a r e d from l i t h i u m (6 g . )
and 1 - c h l o r o c y c l o h e x e n e (15 g . ) i n e t h e r (150 m l . ) and
th e s o l u t i o n h e a t e d u n d e r r e f l u x f o r 1 h r . and t h e n
c o o le d d u r i n g th e a d d i t i o n o f w a t e r (100 m l . ) . The
e t h e r e a l l a y e r was washed w i t h w a t e r , d r i e d , and h e a t e d
u nder r e f l u x f o r 2 h r . w i t h m e th y l i o d i d e (10 m l . ) . The
r e s u l t i n g s o l i d v/as r e c r y s t a l l i s e d from c h l o r o f o r m / e t h y l
a c e t a t e t o g i v e c y c l o h e x - l - e n y l m e t h y l d ip h e n y lp h o s p h o n i u m
-119-
i o d i d e ( l 6 g . ) , m .p . 2 2 5 -2 2 6 ° .
R e a c t i o n o f T r ip h e n y lp h o s p h in e w i t h C y c lo o c te n e
o x i d e . - T r i p h e n y lp h o s p h in e ( 6 . 8 g . ) and 1 , 2 - e p o x y c y c l o o c t e n e
( 5 . 2 g . ) were h e a t e d t o g e t h e r i n a s e a l e d tu be a t 210° f o r
6 d ay s and th e p r o d u c t e x t r a c t e d w i t h e t h a n o l (100 m l . ) .
G . l . c . (6 m. a p i e z o n L column, a t 140°) showed t h e p r e s e n c e
o f c y c l o o c t e n e ( 2 0 0 ) . The s o l u t i o n was e v a p o r a t e d , and t h e
r e s i d u e a d s o r b e d on b a s i c a lu m in a . E l u t i o n w i t h l i g h t
p e t r o l e u m ( b . p . 4 0 - 6 0 ° ) gave t r i p h e n y l p h o s p h i n e ( 2 . 3 g . ) ,
m .p . and mixed m .p . ( f ro m e t h y l a c e t a t e - p e t r o l ) 7 8 - 7 9 ° ;
e l u t i o n w i th e t h e r - m e t h a n o l ( 2 0 :1 ) gave t r i p h e n y l p h o s p h i n e
o x id e ( 4 . 2 g . ) , m .p . and mixed m .p . ( f rom e t h y l a c e t a t e )
157-158°C.
R e a c t i o n o f t r a n s - s t i l b e n e ox ide w i th T r i p h e n y l -
p h o s p h in e . - T r i p h e n y l p h o s p h i n e ( 6 . 8 g . ) and t r a n s - s t i l b e n e
o x ide ( 4 . 9 g . ) were h e a t e d t o g e t h e r a t 180° f o r 4 days and
the p r o d u c t e x t r a c t e d w i t h e t h a n o l (80 m l . ) . G . l . c . (6 m.
a p i e z o n column, a t 250°) showed th e p r e s e n c e of t r a n s - s t i l b e n e
(9^0 and c i s - s t i l b e n e ( ^ ) . The s o l u t i o n was e v a p o r a t e d
and t h e r e s i d u e a d s o r b e d on b a s i c a lu m in a . E l u t i o n w i t h
l i g h t p e t r o l e u m ( b . p . 4 0 - 6 0 ° ) gave t r a n s - s t i l b e n e ( O . l g . )
m .p . and mixed m .p . 1 24 -1 2 5 ° ; e l u t i o n w i th l i g h t p e t r o l e u m -
e t h e r ( 4 : 1 ) gave t r i p h e n y l p h o s p h i n e ( 1 . 4 g . ) , m .p . and mixed
- 1 2 0 -
m.p* 7 8 - 7 9 ° ; and e l u t i o n w i t h e t h e r - m e t h a n o l ( 2 0 : 1 ) gave
t r i p h e n y l p h o s p h i n e ox ide (4«5 g . ) , m .p . and m ixed m.p.
( f rom e t h y l a c e t a t e ) 1 5 7 -1 5 8 ° .
—1 2 0 a —
Abnormal Q u a t e r n i s a t i o n R e a c t i o n s o f Some A c t i v a t e d
A l k y l H a l i d e s .
( a ) R e a c t i o n s P r o c e e d i n g v i a Eno l-Phosphon ium S a l t s .
Most p r i m a r y a l k y l h a l i d e s q u a t e r n i s e n o r m a l ly
w i t h t e r t i a r y p h o s p h i n e s , n u c l e o p h i l i c a t t a c k by th e
p h o s p h in e a t c a r b o n , l e a d i n g t o d i s p l a c e m e n t o f h a l i d e
i o n and th e f o r m a t i o n o f a phosphonium s a l t .
R3P + R * - C H 2, - X R g P - C H s - R * X"
However, t h e r e a r e a number o f exam ples o f
a b n o rm a l r e a c t i o n s b e tw ee n p h o s p h i n e s and o r g a n i c h a l i d e s .
One g ro u p of t h e s e d a th e r e a c t i o n o f p h o s p h i n e s w i t h
a l k y l h a l i d e s c o n t a i n i n g a c t i v a t i n g g ro u p s a t t a c h e d t o
t h e a - c a r b o n atom.
When a l l o w e d t o r e a c t w i t h t e r t i a r y p h o s p h i n e s ,
c e r t a i n a - h a l o k e t o n e s do n o t g i v e th e e x p e c t e d p - k e t o p h o s -
phonium s a l t s , b u t i n s t e a d , p r o d u c t s , which on t r e a t m e n t
w i t h a l c o h o l s g i v e t e r t i a r y p h o sp h in e o x i d e s , d e - h a l o g e n a t e d1 6 9 ,1^0
k e t o n e s and a l k y l h a l i d e s .
0 = GRnP +
— G — H a l
- 1 2 1 -
R3P — G — GO — H al
Normal Route
C r y s t a l l i n e body. Abnormal R o u te .
R*OH
aR3 PO + — “ G*—
H4- RdHal,
Bromides show a g r e a t e r t e n d e n c y t o r e a c t
a b n o rm a l ly t h a n th e c o r r e s p o n d i n g c h l o r i d e s , a l t h o u g h
m o n o -h a lo m e th y lk e to n e s do n o t u s u a l l y show th e abnorm al16±
r e a c t i o n w h a te v e r th e h a l o g e n . The abnorm al r e a c t i o n
becomes more l i k e l y a s t h e number of h a l o g e n s u b s t i t u e n t s
on t h e a - c a r b o n i n c r e a s e s , f o r exam ple , e v e n when t h e
h a lo g e n i s c h l o r i n e , compounds l i k e c h l o r a l undergo an
abnorm al r e a c t i o n w i t h t r i p h e n y l p h o s p h i n e i n a v i o l e n t l y1 6 9
e x o th e r m ic manner.
The i n t e r m e d i a t e compound form ed i n t h e s e r e a c t i o n s
h a s b een f o r m u l a t e d a s th e en o l-p ho sp ho n ium s a l t . (186)1 6 9 ,16 0
-122-
+
R»” R.»R'» ^R»** .i0
(186) R " - G - HR t t l
162S p e z i a l e a n d P a n t o s f i n a l l y e s t a b l i s h e d t h e
s t r u c t u r e o f t h e i n t e r m e d i a t e ( 1 8 8 ) i n t h e r e a c t i o n o f
t h e c h l o r o k e t o n e ( 1 8 7 ) w i t h t r i p h e n y l p h o s p h i n e , b y e l e m e n t a l
a n a l y s i s , t h e a b s e n c e o f a c a r b o n y l s t r e t c h i n g f r e q u e n c y
i n i t s i n f r a r e d s p e c t r u m a n d t h e p r e s e n c e o f a p h o s p h o n i u m
s a l t l i k e r e s o n a n c e i n i t s P®^ N . M . R . s p e c t r u m .
PhgP + P h j a G - G - P h P h 2 G = G - P hs(187) (1 88 )
I +G1 Ù O - P P h a G1
I t s e e m s l i k e l y t h a t i n t e r m e d i a t e s o f t h e t y p e
( 1 8 6 ) d o n o t d e c o m p o s e b e c a u s e t h e l i k e l y h o o d o f n u c l e o p h i l i c
a t t a c k b y h a l o g e n a t a v i n y l i c c a r b o n a t o m i s s m a l l . T h i s1 5 9 ,163 ,16
c a n b e c o m p a r e d w i t h t h e I l i c h a e l i s - A r b u s o v r e a c t i o n .
-123-
The eno l-ph o sph o n iu m s a l t (188) i s a M i c h a e l i s - Arbusov
r e a c t i o n i n t e r m e d i a t e and t h e s e w i l l n o t decompose when
h a l i d e a t t a c k i s r e q u i r e d on an a r o m a t i c n u c l e u s , a n a lo g o u s
to t h e v i n y l i c sys tem ( 1 8 8 ) . The r e a c t i o n of t h e s e sy s te m s
w i t h a l c o h o l s may be e x p l a i n e d by t r a n s e s t é r i f i c a t i o n to g i v e
a n a Iko x y—phosphonium s a l t ( 1 8 9 ) , which can t h e n undergo
t h e seco n d s t a g e o f t h e M i c h a e l i s - A r b u s o v r e a c t i o n .
ROH ^ 0 = // II H a l" I
{ 1 8 9 )A H
\— PC + RHal. /
E nol-phosphon ium s a l t s have n o t o n ly been i s o l a t e d
from t h e r e a c t i o n o f a —h a l o k e t o n e s w i t h t e r t i a r y p h o s p h i n e s ,
e t h y l t r i c h l o r o a c e t a t e , c h l o r o a c e t y l c h l o r i d e , and
bromomalonic e s t e r have a l l been shown t o g i v e en o l-p h o sp h o n iu m159
s a l t s w i t h t e r t i a r y p h o s p h i n e s .
Many o t h e r r e a c t i o n s o f t e r t i a r y p h o s p h i n e s w i t h
h a lo g e n compounds, t o g i v e p r o d u c t s o t h e r t h a n t l ioseexpec ted
by no rm al q u a t e r n i s a t i o n , c a n be e x p l a i n e d by th e p o s t u l a t i o n
o f e n o l -p ho sp ho n ium s a l t i n t e r m e d i a t e s .
— 124—
D esy l c h l o r i d e and t r i p h e n y l p h o s p h i n e r e a c t t o
g iv e d i p h e n y l a c e t y l e n e , t r i p h e n y l p h o s p h i n e o x ide and h y d ro g e n170
c h l o r i d e .
PhnP + P h - G O - G H O l - P hP h ^
P h a r
r \ ■E•g z z i g :
G1^ P h
( 190)
PhaPO -F P h - G = G - P h + HGl
T h is may be e x p l a i n e d by i n i t i a l f o r m a t i o n o f t h e
e n o l-p h osp h on iu m s a l t ( 1 9 0 ) , f o l l o w e d by d e c o m p o s i t i o n a s
shown.
E nol-phosphon ium s a l t s may be p o s t u l a t e d a s
i n t e r m e d i a t e s i n th e r e a c t i o n of N-bromo-amides ( l 9 l ) w i th
t r i p h e n y l p h o s p h i n e , which l e a d t o n i t r i l e , p h o s p h in e ox ide170
and h yd ro g en b ro m id e .
RGONHBr + PhaP
(191 )
> P \
PhaPBr
PhaPO + RGN
+■ HBr
-125-
166S p e z i a l e and Sm ith have s t u d i e d t h e r e a c t i o n
o f t r i p h e n y l p h o s p h i n e w i t h N - d h l o r o - N - e th y l b e n z a m i d e ( 1 9 2 ) ,
where any e n o l -ph o sph o n iu m s a l t fo rm ed w i l l n o t be a b l e t o
d e p r o t o n a t e . They fo u n d t h a t th e p r o d u c t s were t r i p h e n y l
p h o s p h i n e ox ide and N - e t h y l b e n z l m i d o y l c h l o r i d e ( 1 9 4 ) . I t
i s s u g g e s t e d t h a t th e eno l-p h o sp h o n iu m s a l t (193) i s
i n i t i a l l y formed and t h e n a t t a c k o f h a l i d e i o n on t h i s
l e a d s t o th e p r o d u c t s .
Ph-CON.\
G1 PhaP
E t
(1 9 2 )
P h - C = N E t
PPho
i(193)
P h aP O + P h - C = H S t
C l(194)
H a l i d e a t t a c k i n t h i s w a y o f f e r s a n a l t e r n a t i v e e x p l a n a t i o n
t o d e p r o t o n a t i o n i n t h e d e c o m p o s i t i o n o f t h e e n o l - p h o s p h o n i u m
s a l t s d e s c r i b e d a b o v e . T h e u n s t a b l e u n s a t u r a t e d h a l o g e n
c o m p o u n d ( 1 9 3 ) s o f o r m e d , u n d e r g o i n g s p o n t a n e o u s d e h y d r o -
h a l o g e n a t i o n .
—126^
T % » ^ l A< v X = Y - P 0 + H a l - X = Y - Hf N /
+ / ° '1' (195 )P - X = Y + H H a l .
The r e a c t i o n s o f N , N - d i s u b s t i t u t e d t r i c h l o r o —
a c e ta m i d e s (196) w i t h t r i a l k y l p h o s p h i t e s and t e r t i a r y16 6
p h o s p h i n e s h ave b e e n s t u d i e d by S p e z i a l e and Freeman.
The p r o d u c t s a r e t r i c h l o r o v i n y l a m i n e s (197) and th e
c o r r e s p o n d i n g t r i a l k y l p h o s p h a t e o r t e r t i a r y p h o s p h in e
o x i d e .
C l NRg
G l a CONRa + R ' a P -» ' ^ G = G + R ’aP O
' C l ' ^ G l
(196) (197)
I t i s s u g g e s t e d t h a t th e en o l-p h o sp h o n iu m s a l t
( 198 ) i s i n i t i a l l y fo rm ed , and t h i s i s decomposed by a t t a c k
o f h a l i d e i o n a t t h e a c t i v a t e d v i n y l i c c a r b o n a tom.
0 J 7Clgj GONRg + Rg P —> Clg C izzrC—NRg p r o d u c t s
( 198)
-127-
A p o s s i b l e a l t e r n a t i v e t o t h i s mechanism h a s b e e n16 5
s u g g e s t e d . The lo n e p a i r o f e l e c t r o n s on n i t r o g e n may
h e l p t o d i s p l a c e th e p h o s p h in e o x ide d i r e c t l y .
r *3p ^ . o rr ^ C = CGlg R ’aPO + R 2 N = C = C G l3
G1" ,0= CGlg
RgN'"
(b ) The Mechanism o f E n o l —Phosphonium S a l t F o r m a t i o n .
A co m p re h en s iv e s t u d y o f t h i s h a s been c a r r i e d167
o u t . Assuming t h a t th e a t t a c k o f th e p h o sp h o ru s compound16 8
i s n u c l e o p h i l i c , which h a s been v e r i f i e d by S p e z i a l e ^ a l ,
t h e r e a r e f i v e p o s s i b l e ways i n which t h i s i n i t i a l a t t a c k
may t a k e p l a c e ,
( a ) a t t h e h a l o g e n b e a r i n g c a r b o n atom,
(b ) a t th e c a r b o n y l c a rb o n a tom ,
( c ) a t t h e c a r b o n y l oxygen a to m ,
(d ) a t th e h a lo g e n a tom, and
(e ) i n a f i v e membered c y c l i c r e a c t i o n t o g i v e a
p e n t a —c o v a l e n t p h o sp h o ru s i n t e r m e d i a t e .
-12 8 -
167P o s s i b i l i t i e s ( a ) and (b) have b e e n shown t o be u n l i k e l y .
D i s t i n c t i o n be tw een t h e r e m a in in g p o s s i b l e modes o f a t t a c k167 ,169
h a s b een th e s u b j e c t o f much d i s c u s s i o n , and no
a b s o l u t e p r o o f h a s y e t be en p u t f o r w a r d a s t o t h e t r u e mode
o f a t t a c k . However, i t h a s been shown t h a t the r e a c t i o n c an ,
i n th e a - h a l o k e t o n e c a s e a t l e a s t , p r o c e e d by e i t h e r a n a c i d
c a t a l y s e d , o r a n o n - a c i d c a t a l y s e d , m echan ism (depend ing upon167
t h e c o n d i t i o n s u s e d .
( c ) The R e a c t i o n o f T r i p h e n y l p h o s p h i n e w i t h d - B r o m o - l - N i t r o -
a l k a n e s .
I n g e n e r a l 1 - b r o m o - l - n i t r o a l k a n e s r e a c t w i t h
t r i p h e n y l p h o s p h i n e to g iv e p h o sp h in e o x i d e , n i t r i l e and
p h o sp h in e o x id e h y d ro b ro m id e . However, b ro m o n i t ro m e th a n e
and 1 -brom 0- 1—n i t r o e t h a n e have b een shown a l s o t o g iv e s a l t s ,
which were o r i g i n a l l y f o r m u l a t e d a s a - n i t r o a l k y l - p h o s p h o n i u m171
b r o m id e s , m a in ly on t h e e v id e n c e t h a t t h e s a l t from
b ro m o n i t ro m e th an e and t r i p h e n y l p h o s p h i n e gave p h o sp h in e o x id e
and f u l m i n i c a c i d when t r e a t e d w i t h aqueous a l k a l i a t 0 ° .
T h i s r e a c t i o n was th o u g h t t o p r o c e e d v i a t h e p h o s p h o b e t a i n e
( 1 9 9 ) .
-1 2 9 -
+ + NaOH + - +P h a P - C H g - F ^ B f ----------- > P h o P - C H - NA ^ 0
Phg l / HPho.RO A ç / .
^ 1+ (199)H C =H O , - / \ -
0 0
I t was hoped t o e x t e n d t h i s r e a c t i o n t o th e
p r e p a r a t i o n o f a l i p h a t i c n i t r i l e o x i d e s by t r e a t m e n t of
t h e s a l t from t r i p h e n y l p h o s p h i n e a n d 1 - b r o m o - 1 - n i t r o e t h a n e
w i t h aq ueous sodium h y d r o x i d e . However , when t h i s v/as1 7 0
c a r r i e d out , no n i t r i l e o x id e c o u l d be d e t e c t e d , even
i n t h e p r e s e n c e o f s t i l b e n e , which r e a d i l y c o n d e n se s wit&17 2
n i t r i l e o x id e s t o g iv e A ® - i s o x a z o l i n e s .
R e i n v e s t i g a t i o n of t h e s e r e a c t i o n s h a s l e d t o
d i f f e r e n t c o n c l u s i o n s . B ro m o n i t r o m e th a n e , 1 - b r o m o - 1 - n i t r o -
e th a n e and 1 - b r o m o - l - n i t r o p r o p a n e have a l l been shown t o
g iv e s a l t s w i t h t r i p h e n y l p h o s p h i n e ( a l t h o u g h t h a t from
1 - b r o m o - l - n i t r o p r o p a n e was o b t a i n e d i n v e r y s m a l l y i e l d ) .
I f t h e homologous s e r i e s i s e x te n d e d f u r t h e r t h e r e a c t i o n
g i v e s no s a l t , b u t o n ly p h o s p h in e o x id e h y d ro b ro m id e and
n i t r i l e , which a r e a l s o fo rm ed i n s m a l l y i e l d t o g e t h e r w i t h
-130-
t h e above s a l t s . The r e a c t i o n a p p e a r s t o be e x t r e m e ly
s e n s i t i v e to t e m p e r a t u r e . I f t h e a d d i t i o n o f th e bromo—
compound, t o th e p h o s p h i n e , i s n o t c a r r i e d o u t s t r i c t l y a t
3 ° , o r b e lo w , th e seco n d r e a c t i o n , t o g i v e n i t r i l e and
p h o s p h in e o x id e h y d r o b r o m id e , p r e d o m in a te s e ven i n th e
b ro m o n i t ro m e th a n e c a s e .
I t was fo u nd t h a t t h e optimum r e a c t i o n was t h a t
b e tw een two m o le s o f p h o sp h in e and one mole o f bromo-compound
t o g i v e th e s a l t and p h o sp h in e o x i d e .
2PhoP + RCHBr.NOg S a l t + PhaPO
These s a l t s were shown to be a - h y d r o x y ^ im in o p h o s -
phonium b rom ides ( 2 0 0 ) .
P h o P - G R z i F - OH B r"
( 200)
The h y d r o x y l g r o u p s o f th e s a l t s a r e a p p a r e n t
i n t h e i n f r a r e d a t < ^ 2 , 7 5 0 cm.”^ , and t h e N.M.R. sp e c t ru m
o f t h e s a l t (200; R = Me) shows th e a b se n c e o f h y d ro g e n on
th e a - c a r b o n atom ( d o u b l e t a t 7 * 8 ^ , = IC c . p . s . ) . The
s t a b i l i t y o f th e s a l t s t o a l k a l i n e h y d r o l y s i s i n c r e a s e d
m a rk e d ly from R = H t o R = E t . T h is made i t p o s s i b l e to f o l l o w
th e r e a c t i o n i n th e c a s e o f th e s a l t (200 ; R = Me) u s i n g an
-131-
N.LI.R. s p e c t r o m e t e r . I t v/as found t h a t t h e e t h y l and
p r o p y l s a l t s (200; R = Me and E t ) were s o l u b l e i n aqueous
sodium h y d r o x i d e , f r o m which s o l u t i o n t h e y c o u ld be
r e p r e c i p i t a t e d by th e a d d i t i o n o f a c i d . I f a l lo w e d to
s t a n d a t room t e m p e r a t u r e o v e r n i g h t , o r warmed to 50° f o r
f i v e m i n u t e s , t h e s e s o l u t i o n s decomposed t o p h o sp h in e o x id e
and n i t r i l e .
+ NaOHP hQ p-C R = NOH Br"--------------y PhgPO + RON
T h is r e a c t i o n was c a r r i e d o u t i n t h e sample
w e l l o f th e N.M.R. s p e c t r o m e t e r by d i s s o l v i n g t h e s a l t
(200 ; R= Me) i n NaOD/DgO and t a k i n g a s e r i e s o f s p e c t r a
a t i n t e r v a l s o f one m in u te a t 4 0 ° . The d o u b l e t a t 7 . 8 ^
due t o th e m e th y l g roup s t e a d i l y d e c r e a s e d i n i n t e n s i t y
and was r e p l a c e d by a s i n g l e t a t 8 . 0 5 ^ , due t o a c e t o n i t r i l e ,
The a l k a l i n e h y d r o l y s i s p re s u m a b ly i n v o l v e s th e
i n i t i a l d e p r o t o n a t i o n o f t h e h y d r o x y l g roup t o g i v e th e
i n t e r m e d i a t e ( 2 0 l ) , which th e n e l i m i n a t e s p h o sp h in e o x id e t o
g iv e t h e n i t r i l e .
Br- ^RC=K
H O ^( 201)
-132-
A c id h y d r o l y s i s of t h e s e compounds r e q u i r e s f a r
more v i g o r o u s c o n d i t i o n s , and t h e c o u r s e depends t o a
l a r g e e x t e n t on a c i d c o n c e n t r a t i o n . I n 2^ h y d r o c h l o r i c
a c i d r e f l u x i n g f o r two o r t h r e e h o u r s l e a d s m a in ly t o
p h o sp h in e o x id e and n i t r i l e , h o w e v e r , i n 12N h y d r o c h l o r i c
a c i d t h e m a jo r p r o d u c t s a r e t r i p h e n y l p h o s p h i n e , h y d r o x y lamine
( i s o l a t e d as b e n za ld o x im e) and c a r b o x y l i c a c i d . T h i s i s
b e s t e x p l a i n e d by t h e com p e t in g r e a c t i o n of h y d r o l y s i s by
w a t e r .
The f o r m a t i o n o f h y d ro x y lam in e and c a r b o x y l i c a c i d
p r o b a b l y goes t h r o u g h t h e i n t e r m e d i a t e (202) which f u r t h e r
h y d r o l y s e s to p h o s p h in e and c a r b o x y l i c a c i d .
Pha .P- CR = N -O H
B r"
R+ I
P h o P - C = 0
(262)
PhoP + R'COOH
The mode of f o r m a t i o n o f t h e s e s a l t s i s , a s y e t ,
o b s c u r e . The r e a c t i o n may i n f a c t p r o c e e d v i a a t r u e
n i t r o p h o s p h o n iu m s a l t ( 2 0 3 ) , which i s t h e n d e - o x y g e n a t e d by
p h o s p h in e a s shown to g iv e th e i n t e r m e d i a t e ( 2 0 4 ) .
M i g r a t i o n of a p r o t o n w i l l t h e n l e a d t o th e o b s e r v e d
p r o d u c t .
PhgP + BrCHR.NOg
PhsP
Br I IN
OH
4
-133-
P R . Î H
r ^ HBr
(203)
A:PPhs
P h g P ^ y t
-
^ 0 "
(204)
Br+- PhaPO
The f o r m a t i o n o f n i t r i l e and p h o sp h in e o x id e
c o u l d p r o c e e d v i a a n e n o l -ph o sp h o n iu m s a l t of the type
( 2 0 3 ) , which decomposes t o g i v e n i t r i l e ox ide an d p h o sp h in e
o x i d e , th e n i t r i l e o x ide b e in g d e -o x y g e n a t e d by f u r t h e r
p h o s p h i n e .
RI + /
PhaP + B r - C H ^ N ^:0
Br"
^ P P h a( 205)
R - C 3 [ + PhaPO < R - C = N - 0 + PhaPO
-134-
A n a l t e r n a t i v e m e c h a n i s m f o r t h e f o r m a t i o n o f
t h e s e s a l t s i n v o l v e s t h e i n i t i a l f o r m a t i o n o f n i t r i l e o x i d e
a n d t r i p h e n y l p h o s p h i n e o x i d e v i a t h e i n t e r m e d i a t e ( 2 0 5 ) .
A t t a c k o f t r i p h e n y l p h o s p h i n e , o r t r i p h e n y l p h o s p h i n e h y d r o -
b r o m i d e , o n t h e n i t r i l e o x i d e c a n t h e n l e a d t o ( 2 0 6 ) w h i c h
m a y p r o t o n a t e m o r e r a p i d l y t h a n i t c a n e l i m i n a t e u n d e r t h e
a c i d i c c o n d i t i o n s .
+ -^ c a - 0 Phg.p E
II (206)
H B r
+PhaP.
Br . ..^OH
T h i s i s s u p p o r t e d t o som e e s t t e n t b y t h e r a p i d d e c r e a s e i n
y i e l d o f t h e s a l t i n g o i n g f r o m R = H t o R = GgHg , t h e i n d u c t i v e
e f f e c t o f t h e a l k y l g r o u p d e c r e a s i n g t h e l i k e l y h o o d o f
n u c l e o p h i l i c a t t a c k o n t h e c a r b o n o f t h e n i t r i l e o x i d e a n d
p r e f e r e n t i a l l y a l l o w i n g d e o x y g e n a t i o n t o t a k e p l a c e *
-135 -
1.73Z b i r a l h a s c a r r i e d o u t t h e r e a c t i o n of
p h o s p h o r a n e s w i t h e t h y l n i t r i t e and shown t h a t , i n t h e c a s e
o f p h o s p h o r a n e s w i t h a h y d ro g en on th e a - c a r b o n a tom ,
n i t r i l e s and p h o sp h in e o x i d e s a r e p r o d u c e d . T h i s r e a c t i o n
p r e s u m a b ly goes t h r o u g h an i n t e r m e d i a t e s i m i l a r t o ( 2 0 3 ) .
However, t h e a n io n w i l l be e th o x i d e i n t h i s c a s e , w h ich can
remove an a - p r o t o n t o g iv e t h e p h o s p h o b e t a i n e ( 2 0 7 ) . T h i s
c an t h e n e l i m i n a t e a s shown. I n our c a s e t h i s ty p e o fth e
e l i m i n a t i o n i s h i n d e r e d byÿ^lack o f a s u f f i c i e n t l y p o w e r f u l
base*
PhaP= C H - R + EtONO P h g P ^ ^ R
PhaPO+ 4---------- * ? | | + EtOH>RON 4:
(207)
The r e a c t i o n o f a r o m a t i c n i t r o s o compounds w i t h90
p h o sp h o ra n e s i s a l s o a n a l o g o u s , t h e p r o d u c t s b e i n g
p h o sp h in e o x id e and S c h i f f s b a s e , p r o b a b l y fo rm ed v i a t h e
- 1 3 6 -
i n t e r m e d i a t e b e t a l n e ( 208 ) ,
PhaE=CHPh + PMTO -> PII3 P , P h
- FI ( 208)
PhaPO + PhCH = NPh
I n an a t t e m p t t o p r e p a r e a t r u e a - n i t r o p h o s p h o n i u m
s a l t , e t h y l n i t r a t e was a l l o w e d t o r e a c t w i t h b e n z y l i d e n e -
t r i p h e n y l p h o s p h o r a n e . \7hen t h i s r e a c t i o n was c a r r i e d ou t i n
t h e p r e s e n c e o f t r i p h e n y l p h o s p h i n e , t r i p h e n y l p h o s p h i n e o x id e
and b e n z o n i t r i l e were fo rm ed , p r e s u m a b ly by a mechanism173
s i m i l a r t o t h a t o f Z b i r a l , w i t h f i n a l d e o x y g e n a t io n o f
th e n i t r i l e ox ide by p h o s p h i n e .
Pho P = CH - Ph + E tONOg -> Phg P ^OEt
0 ^ 0
P h « K .P h PhaPO
_ P h - G = N - 0
j p h a P
PhaPO + P h - G = N
-137-
o t h e r a t t e m p t s t o p r e p a r e a - n i t r o p h o s p h o n i u m
s a l t s w e r e e q u a l l y u n s u c c e s s f u l .
T h e r e a c t i o n o f s o d i u m d i p h e n y l p h o s p h i d e w i t h
b r o m o n i t r o m e t h a n e g a v e d i p h e n y l p h o s p h i n i c a c i d a s t h e o n l y
i s o l a t a b l e p r o d u c t , a s d i d t h e r e a c t i o n b e t w e e n t h e s o d i u m
s a l t o f n i t r o m e t h a n e a n d c h l o r o d i p h e n y l p h o s p h i n e . R e a c t i o n s
o f n i t r y l c h l o r i d e (NOgCl) w i t h p h o s p h o r a n e s g a v e n o
c r y s t a l l i n e p r o d u c t s .
T h i s w o r k m e a n s t h a t , a s y e t , n o a - n i t r o a l k y l p h o s -1 6
p h o n i u m s a l t s h a v e b e e n i s o l a t e d , a l t h o u g h H o r n e r h a s
m a de a - n i t r o a r s o r a n e s b y t h e r e a c t i o n o f n i t r o p h e n y l m e t h a n e
w i t h d i c h l o r o t r i p h e n y l a r s o r a n e i n t h e p r e s e n c e o f
t r i e t h y l a m i n e .
^ P h Ph ^PhsAsClg + CHb phgAs = + 2EtaKH
^ NOg, KOg C l"
T he a n a l o g o u s r e a c t i o n w i t h d i c h l o r o t r i p h e n y l -
p h o s p h o r a n e g a v e o n l y p h o s p h i n e o x i d e a n d b e n z o n i t r i l e . T h i s
m u s t b e d u e t o t h e m u c h d e c r e a s e d o x y g e n a f f i n i t y o f a r s e n i c
w h e n c o m p a r e d w i t h p h o s p h o r u s . T h i s i s b o r n e o u t b y t h e
f o r m a t i o n o f e p o x i d e s f r o m m any a r s e n i c b e t a i n e s , w h e r e t h e
a n a l o g o u s p h o s p h o r u s b e t a i n e s g i v e o l e f i n s . T h u s a t t a c k o f
- 1 3 8 -
oxygen i s on c a r b o n r a t h e r t h a n th e p o s i t i v e l y c h a r g e d
a r s e n i c atom, a l t h o u g h c e r t a i n a r s e n i c b e t a i n e s have b e en174:
shown t o g i v e q u i t e h i g h y i e l d s o f o l e f i n s .
^GRgI P h a A s + 0 ^ [CRa \ ^ C R a
' ^ 0
PhaP, _CRa P haP O
"0^
4r GRg — GRg
-139 -
E x p e r i m e n t a l
A l l e x p e r i m e n t s u s i n g p h o s p h o r a n e s , and s i m i l a r
u n s t a b l e compounds, were c a r r i e d ou t u n d e r an o x y g e n - f r e e
n i t r o g e n a tm o sp h e re . A l l s o l v e n t s were d r i e d b e f o r e u s e .
M e l t i n g p o i n t s were c o r r e c t e d .
175P r e p a r a t i o n o f B ro m o n i t ro m e th a n e . - To a s o l u t i o n o f
sodium (.3*3 g. ) i n e t h a n o l (70 g . ) was added a s o l u t i o n of
n i t r o m e t h a n e (10 g . ) i n e t h a n o l (30 g . ) v / i th s t i r r i n g . The
s o l i d sodium s a l t o f n i t r o m e t h a n e was f i l t e r e d and washed
v / i th e t h e r (3 x 30 m l . ) . (The sodium s a l t s h o u l d be u se d
d i r e c t l y , a s an e x p l o s i o n o c c u r r e d on d r y i n g and s t o r a g e ) .
To th e s o l i d sodium s a l t p r e p a r e d i n t h i s v/ay v/as s lo w ly
added , w i t h i c e c o o l i n g , a s o l u t i o n of b rom ine (22 g . ) i n
c a rb o n d i s u l p h i d e (100 g . ) w h i l e t h e r e a c t i o n m i x t u r e was
v i g o r o u s l y s t i r r e d . The c a r b o n d i s u l p h i d e s o l u t i o n was
f i l t e r e d and washed w i t h w a t e r (3 x 40 m l . ) . D ry in g
(NagSOa), e v a p o r a t i o n and d i s t i l l a t i o n gave b r o m o n i t r o
m ethane (7 g . ) b . p . 146- 130 ° ( l i t . b , p . 149 ° ) .
S i m i l a r l y p r e p a r e d were 1 - b r o m o - 1 - n i t r o e t h a n e177/
b .p * 143° ( l i t . 1 4 6 -7 3 and 1 - b r o m o - l - n i t r o - p r o p a n e b . p .
163- 166° ( l i t . ^ ^ ^ ^ 160- 163° ) .
—i4o—
R e a c t i o n o f B rom onit rom ethgne w i t h T r i p h e n y l p h o s p h i n e . -
A s o l u t i o n o f b ro m o n i t ro m e th a n e (7 g . ) i n benzene (13 m l . )
was added s lo w ly t o a s o l u t i o n o f t r i p h e n y l p h o s p h i n e (26 g . )
i n benzen e (30 m l . ) so t h a t th e t e m p e r a t u r e d i d n o t r i s e
above 3 ° , and t h e r e s u l t i n g s u s p e n s i o n s e t a s i d e a t < 3 ° f o r
1 h o u r . F i l t r a t i o n gave h y d r o x y i m i n o m e t h y l t r i p h e n y l p h o s -
phonium bromide (13 g . ) , m .p . ( f rom n i t r o m e t h a n e - e t h y l
a c e t a t e ) l66°C (decom p.) (Found: C, 39*0; H, 4 . 3 ; N, 3 . 6 .
OigHiYBrNOP r e q u i r e s C, 3 9 .0 3 ; H, 4 . 4 ; N, 3 . 6 0 ) . E v a p o r a t i o n
o f t h e f i l t r a t e and r e c r y s t a l l i s a t i o n from e t h y l a c e t a t e
gave t r i p h e n y l p h o s p h i n e o x id e ( 1 2 . 3 g . ) , m .p . and m ixed
m .p . 1 3 7 -13 8 ° .
I n a s i m i l a r way, 1 - b r o m o - l - n i t r o e t h a n e gave
a - h y d r o x y i m in o e t h y l t r i p h e n y l p h o s p h o n i u m brom ide ( 6 ^ ) , m .p .
( f rom c h l o r o f o r m - e t h y l a c e t a t e ) 133-134° (Found: G, 3 9 .8 3 ;
H, 4 . 9 ; N, 3 . 3 . GgoHigBrNOP r e q u i r e s C, 3 9 .9 ; H, 4 . 7 3 ;
N, 3 . 3 0 ) * and t r i p h e n y l p h o s p h i n e o x ide ( 80^5) ;
-141 -
l - b r o m o - l - n i t r o p r o p a n e ggve g - h y d r o x y i m i n o p r o p y l t r i p h e n y l -
phosphonium bromide ( l6^o) , m .p . 152-154® (Pound: G, 6 0 .7 6 ;
H, 5 . 2 ; N, 3 . 3 ; 7*4 . CsiHgiBrNOP r e q u i r e s C, 6 0 .8 ;
H, 5 . 1 ; N, 3 . 4 ; p , 7 . 5 ^ ) . The f i l t r a t e from t h e l a s t
r e a c t i o n was shown by g . l . c . [ C a p i l l a r y column (50 m. x
0 . 5 mm.) c o a t e d w i t h p o l y p r o p y l e n e g l y c o l ] t o c o n t a i n
p r o p i o n i t r i l e ( /^ 6O0).
A l k a l i n e H y d r o l y s i s o f These S a l t s . - H y d ro x y im in o m e th y l -
t r ip h e n y lp h o s p h o n iu m brom ide ( 4 . 9 2 g . ) was d i s s o l v e d i n
w a te r (30 m l . ) and e t h a n o l (30 m l . ) , aqueous sodium
h y d r o x i d e ( IN; 13 m l . ) a d d e d , and t h e s u s p e n s i o n s e t a s i d e
a t room t e m p e r a t u r e f o r 15 m in . F i l t r a t i o n gave t r i p h e n y l -
p h o sp h in e o x id e ( 3 . 4 g . ) , m .p . and m ixed m.p* 1 5 7 -158° .
T i t r a t i o n o f t h e f i l t r a t e w i t h s i l v e r n i t r a t e showed t h e
p r e s e n c e o f c y a n i d e i o n ( 2 8 ^ ) .
a - H y d r o x y im i n o e t h y l t r i p h e n y l p h o s p h o n i u m brom ide
and a - h y d r o x y i m in o p r o p y l t r i p h e n y lp h o s p h o n i u m b rom ide b o t h
d i s s o l v e d i n d i l u t e a l k a l i a t room t e m p e r a t u r e to g iv e
s t a b l e s o l u t i o n s from w h ich t h e y c o u l d be r e c o v e r e d on
a c i d i f i c a t i o n . R e f l u x i n g a s o l u t i o n o f g - h y d r o x y i m i n o e t h y l -
t r ip h e n y lp h o s p h o n iu m b ro m id e i n aqueous sodium h y d r o x i d e
s o l u t i o n ( 0 . 5N) f o r 10 m in . g a v e , on c o o l i n g and f i l t r a t i o n .
—1 4 2 —
t r i p h e n y l p h o s p h i n e o x i d e ( Q8%) , m . p . a n d m i x e d m . p .
1 3 7 - 1 5 8 ° . A n a l y s i s o f t h e f i l t r a t e b y g . l . c . [ c a p i l l a r y
c o l u m n ( 5 0 m. x 0 .5 m m .) c o a t e d w i t h p o l y p r o p y l e n e g l y c o l ]
s h o w e d t h e p r e s e n c e o f a c e t o n i t r i l e ( 50^ ) # S i m i l a r l y
g - h y d r o x y i m i n o p r o p y l t r i p h e n y l p h o s p h o n i u m b r o m i d e g a v e
t r i p h e n y l p h o s p h i n e o x i d e ( 91^ ) a n d p r o p i o n i t r i l e (6CÇ0).
A c i d i c H y d r o l y s i s o f T h e s e S a l t s . - A s o l u t i o n o f t h e s a l t
( 1 -2 g . ) i n h y d r o c h l o r i c a c i d (30 m l . ) w a s r e f l u x e d f o r
2 -3 h r . , , t h e r e s u l t i n g s o l u t i o n a n a l y s e d d i r e c t l y f o r
n i t r i l e b y g . l . c . [ c a p i l l a r y c o l u m n ( 5 0 m. x 0 .5 mm.) c o a t e d
w i t h p o l y p r o p y l e n e g l y c o l ] a n d t h e n e x t r a c t e d w i t h c h l o r o f o r m .
T h e e x t r a c t w a s w a s h e d w i t h w a t e r , d r i e d a n d e v a p o r a t e d , a n d
t h e r e s i d u e s e t a s i d e a t r o o m t e m p e r a t u r e o v e r n i g h t i n
b e n z e n e (10 m l . ) c o n t a i n i n g m e t h y l i o d i d e (2 m l . ) . F i l t r a t i o n
g a v e m e t h y l t r i p h e n y l p h o s p h o n i u m i o d i d e , m . p . a n d m i x e d m . p .
1 9 0 - 1 9 2 ° ( f r o m c h l o r o f o r m - e t h y l a c e t a t e ) . E v a p o r a t i o n o f
t h e f i l t r a t e g a v e t r i p h e n y l p h o s p h i n e o x i d e , m . p . a n d m i x e d
m . p . 1 5 7 - 1 3 8 ° ( f r o m e t h y l a c e t a t e ) . T h e y i e l d s a r e g i v e n
i n t h e T a b l e .
-143-
S a l t H y d ro im in o m e th y l -phosphonium
g-H y dro xy im ino - e thy lphosphon ium
g -H y d ro x y im in o -p rop y lph o sp h on iu m
2IT-HC1 12N-HC1 2N-HC1 2N-HC1 12N-HC1
Phg PO 33 12 55 71 T ra c e
Pha,P 57 74 18 T r a c e 67
RON ' 30 60
A s o l u t i o n of h y droxy im inom ethy lphosphon ium brom ide
( 6 , 3 g . ) i n 1 2 N - h y d r o c h lo r i c a c i d (15 m l . ) was r e f l u x e d f o r
3 h r . , c o o l e d , f i l t e r e d , and made a l k a l i n e a t 0° by th e
a d d i t i o n o f 3N-sodium h y d r o x id e * B enza ld eh yd e (2 g . ) was
t h e n a d d e d , th e s o l u t i o n s e t a s i d e a t room t e m p e r a t u r e f o r
1 h r . , and t h e n a c i d i f i e d by th e a d d i t i o n of s o l i d c a r b o n
d i o x i d e . E t h e r e x t r a c t i o n and d i s t i l l a t i o n o f th e e x t r a c t
a t 1 1 0 - 1 2 0 ° /3 mm. gave a l i q u i d ( 1 . 2 g . ) whose i n f r a r e d
sp ec t ru m was a co m p os i te o f e q u a l p a r t s o f benz.aldoxime
and b e n z a ld e h y d e . T h is was r e f l u x e d i n a c e t i c a n h y d r id e
(2 m l . ) f o r 15 min. A n a l y s i s by g . l . c . (6 m. a p i e z o n L
column) showed th e p r e s e n c e o f a p p r o x i m a t e l y e q u a l q u a n t i t i e s
of b e n z a ld e h y d e and b e n z o n i t r i l e .
-144-
R e a c t l o n o f B e n z y l l d e n e t r i p h e n y l p h o s p h o r a n e w i th E t h y l
N i t r a t e . - To a s o l u t i o n o f h e n z y l i d e n e t r i p h e n y l p h o s p h o r a n e ,
from th e phosphonium brom ide (12 g . ) and BuLi (IN; 29 m l . ) ,
i n e t h e r , was added t r i p h e n y l p h o s p h i n e (7 g . ) and th e
s o l u t i o n s t i r r e d u n t i l t h e p h o s p h in e had d i s s o l v e d . To t h i s
s o l u t i o n e t h y l n i t r a t e ( 2 . 6 g . ) , i n e t h e r (10 m l . ) was s l o w l y
added . The r e a c t i o n m i x t u r e v/as t h e n s t i r r e d f o r 2 h o u r s ,
when g . l . c . ( 6 m . a p i e z o n L column a t 180°) on t h e r e a c t i o n
m i x t u r e showed th e p r e s e n c e o f b e n z o n i t r i l e ( 2 8 ^ ) . The
r e a c t i o n m i x t u r e was e v a p o r a t e d , d i s s o l v e d i n c h lo r o f o r m ,
washed w i t h w a t e r and d r i e d . E v a p o r a t i o n gave t r i p h e n y l
p h o sp h in e o x id e ( 3 . 9 g . ) , m .p . and mixed m .p . 1 57 -158° .
R e a c t i o n o f Sodium D ip h e n y lp h o s p h id e w i t h B ro m o n i t ro m e th a n e .
Sodium d ip h e n y l p h o s p h i d e was p r e p a r e d from d i p h e n y l p h o s p h i n e
( l 8 . 6 g . ) and sodium i n t e t r a h y d r o f u r a n (100 m l . ) . To t h i s
s o l u t i o n was added b r o m o n i t ro m e th a n e (13 g . ) i n t e t r a h y d r o
f u r a n (13 m l . ) and th e s o l u t i o n s t i r r e d f o r 1 h r . a t room
t e m p e r a t u r e . The r e s u l t i n g s o l u t i o n was e v a p o r a t e d ,
d i s s o l v e d i n benzen e washed w i t h w a t e r and d r i e d . M ethy l
i o d i d e (13 g . ) was a d d ed , and t h i s s o l u t i o n a l l o w e d t o s t a n d
a t room t e m p e r a t u r e o v e r n i g h t . F i l t r a t i o n gave d i m e t h y l -
d iph en y lph o sp h on iu m i o d i d e (5 g . ) , m .p . and mixed m .p .
-145-
248 - 249° . E v a p o r a t i o n o f t h e f i l t r a t e g a v e , o n t r i t u r a t i o n
w i t h p e t r o l , d i p h e n y l p h o s p h i n i c a c i d ( 1 2 .8 g . ) , m . p . a n d
m i x e d m . p . 191 - 192° .
-I4 5 a -
T h e R e a c t i o n o f A l d e h y d e s a n d K e t o n e s w i t h . T r i v a l e n t
P h o s p h o r u s C o m p o u n d s . - C o n s i d e r a b l e w o r k h a s b e e n
c a r r i e d o u t o n t h e r e a c t i o n s o f c a r b o n y l c o m p o u n d s
w i t h t r i v a l e n t p h o s p h o r u s c o m p o u n d s c o n t a i n i n g a
s u b s t i t u e n t c a p a b l e o f f o r m i n g a s t a b l e a n i o n .
C h l o r o p h o s p h i n e s h a v e b e e n s h o w n t o r e a c t178 ,179 178
r e a d i l y w i t h a l d e h y d e s . C o n a n t f o u n d t h a t
c h l o r o d i p h e n y l p h o s p h i n e a n d b e n z a l d e h y d e r e a c t e d a t
ro o m t e m p e r a t u r e t o g i v e a p r o d u c t w h i c h o n t r e a t m e n t
w i t h w a t e r g a v e a - h y d r o x y b e n z y l d i p h e n y l p h o s p h i n e o x i d e
( 2 0 9 ) .
R .T . HgO phgPOPhCHO + PhgPCl ----------- ^ [X] > I
P h - C H - O H
(209)
S i m i l a r r e a c t i o n s w i t h c h l o r o a c e t a l d e h y d e s
g a v e a n a l o g o u s p r o d u c t s . C h l o r o d i e t h y l p h o s p h i n e a n d
c h l o r a l a t 0 ° g a v e a p r o d u c t w h i c h o n t r e a t m e n t w i t h179
w a t e r g a v e ( 210 ) .
- 1 4 6 -
Q OHE tg P C l + CI3C.CHO - 2^ [X] E t B P - C H - C G l i
( 210)
I f h y d r o g e n s u l p h i d e w as u s e d i n p l a c e o f w a t e r
i n t h e w o r k u p o f t h e s e r e a c t i o n s t h e p h o s p h i n e s u l p h i d e
( 2 1 1 ) a n a l o g o u s t o ( 210 ) w a s o b t a i n e d .
S OH
R g P - C H - C C l e ( 211 )
P h o s p h o r u s t r i h a l i d e s h a v e a l s o b e e n s h o w n t o r e a c t18 0, 181, 182, 18 3, 18 4:, 185
w i t h a l d e h y d e s a n d k e t o n e s . T h e
p r o d u c t s f r o m t h e s e r e a c t i o n s d e p e n d u p o n t h e r e a c t i o n
c o n d i t i o n s . When a n a l d e h y d e a n d p h o s p h o r u s t r i c h l o r i d e a r e
a l l o w e d t o r e a c t a t R . T . , a n d t h e r e a c t i o n m i x t u r e t r e a t e d
w i t h w a t e r , t h e p r o d u c t i s t h e a - h y d r o x y p h o s p h o n i c a c i d, 18 2
( 2 1 2 ) .
OH OHPCI3 + RCHO -► [X] H0 - & - C H - R
( 212)
T h e r e a c t i o n o f p h o s p h o r u s t r i c h l o r i d e w i t h k e t o n e s
i s s i m i l a r t o g i v e , a f t e r t r e a t m e n t w i t h w a t e r , t h e p h o s p h o n i c
—147—
X 185a c i d ( 2 1 3 ) .
OH ^HPCI3 + RCOMe ^ [X] H O - P - Ç - Me
( 213 )
However, when t h e s e r e a c t i o n s a r e c a r r i e d ou t a t
e l e v a t e d t e m p e r a t u r e s t h e p r o d u c t s a r e d i f f e r e n t . I f a
m i x t u r e o f b e n z a ld e h y d e and p h o s p h o ru s t r i c h l o r i d e i s180
h e a t e d , t h e p h o sp h in e o x id e (214) i s p ro d u c e d .
H ea tPhCHO + PC ^j > P h - C H C l - P C l g (214)
The r e a c t i o n b e tw ee n k e t o n e s and p h o sp h o ru s
t r i c h l o r i d e i s a n a l o g o u s , h e a t i n g i n a s e a l e d tu b e a t
200° g i v i n g ( 215 ) .
200° ®RgCO + PCI3 --------------- ^ RgÙ - PClg (^ ^ 5 )
s e a l e dtube
These r e s u l t s may be r a t i o n a l i s e d i n t h e f o l l o w i n g
m anner . The i n i t i a l s t e p i n a l l t h e r e a c t i o n s c o u ld be
n u c l e o p h i l i c a t t a c k o f p h o sp h o ru s on the c a rb o n of th e
c a r b o n y l group i n th e k e t o n e , o r a l d e h y d e , t o g i v e a b e t a i n e
o f t h e typ e ( 216 ) .
—148—
R _ R•f
G O o P :^ C l g P - à - R (216)0 = 0 -► CI3P— ck “6
I f the r e a c t i o n m i x t u r e i s t r e a t e d w i t h w a t e r a t
t h i s s t a g e p r o t o n a t i o n and h y d r o l y s i s w i l l g iv e th e
p h o s p h o n ic a c i d (213 ; Me = R ) . However, i f t h e b e t a i n e
( 216 ) i s h e a t e d i t may r e a r r a n g e , e i t h e r by an i n t r a m o l e c u l a r
mechanism ( 217 ) , o r by an i n t e r m o l e c u l a r mechanism ( 21 8 ) , to
g i v e t h e p h o sp h in e o x id e ( 219 ) .
ClgP^0 01
IC lg P -G R g
(217)
CI2P— c — R
( 219 )
R— G ' PC Ig
(218)
-149-
H o v / e v e r , i t i s p e r h a p s s u r p r i s i n g t h a t c h l o r o p h o s p h i n e s
a r e s u f f i c i e n t l y n u c l e o p h i l i c t o a t t a c k u n a c t i v a t e d k e t o n e s
a n d a l d e h y d e s a t r o o m t e m p e r a t u r e , a l t h o u g h q u i t e p o s s i b l e
t h a t t h e y w i l l a t t a c k a l d e h y d e s l i k e c h l o r a l w h e r e t h e
c a r b o n y l g r o u p i s h i g h l y s u s c e p t i b l e t o n u c l e o p h i l i c a t t a c k .
I n t h e c a s e s o f r o o m t e m p e r a t u r e r e a c t i o n s w i t h u n a c t i v a t e d
a l d e h y d e s a n d k e t o n e s a c e t i c a c i d h a s i n v a r i a b l y b e e n u s e d
a s a s o l v e n t , a n d t h i s may w e l l t a k e p a r t i n t h e r e a c t i o n .
T h e i n i t i a l s t e p m ay b e a t t a c k o f t h e c h l o r o p h o s p h i n e o n t h e
a c e t i c a c i d t o g i v e t h e a c e t o x y p h o s p h i n e a n d h y d r o g e n c h l o r i d e ,
w h i c h w i l l r a p i d l y g i v e s e c o n d a r y p h o s p h i n e o x i d e a n d a c i d
c h l o r i d e . S e c o n d a r y p h o s p h i n e o x i d e s a r e k n o w n t o a d d
r e a d i l y t o a l d e h y d e s a n d k e t o n e s t o g i v e h y d r o x y p h o s p h i n e178 ,186
o x i d e s . C o n a n t h a s i n f a c t i s o l a t e d a c e t y l c h l o r i d e
f r o m t h e s e r e a c t i o n s .
HR g P C l + CHaCOOH E g P - O - C - C H a + H C l
Q 0+ r \ «
CHa Rg P 'n I
RjCO
-» R3 P - O - 1 Ü - C H 3 R g P - H + CH3 COGI
^ - G l
R g P - C R 'g
T h e r e a c t i o n w i t h p h o s p h o r u s t r i c h l o r i d e m a y b e s i m i l a r t o
g i v e t h e a c e t o x y p h o s p h i n e i n i t i a l l y , w h i c h g i v e s t h e s e c o n d a r y
- 1 5 0 -
phosphine. o x id e (220) w i t h h y d ro g e n c h l o r i d e . A t t a c k of
t h i s on th e c a r b o n y l compound and f i n a l l y h y d r o l y s i s w i t h
w a t e r g i v i n g t h e p h o s p h i n i c a c i d ( 2 2 1 ) .
CH3COOH ({P G la ---------------- ) C I3 P - 0 - C - CH3 + HCl
Ç)ClgPH + CH3COCI
i ( 220 )RgCOÇ ÇH HgO H O ^ f i r
C l g P - CRg — 7 ^ P - GRjHcr
( 221)
T e r t i a r y p h o s p h i t e s a l s o r e a c t w i th a ld e h y d e s and
k e t o n e s . T r i a l k y l p h o s p h i t e s r e a c t w i t h p - n i t r o b e n z a l d e h y d e186
t o g i v e p h o s p h o r a t e s ( 2 2 3 ) . P re su m a b ly th e i n i t i a l a t t a c k
i s a t t h e c a r b o n y l c a r b o n to g iv e t h e b e t a i n e ( 2 2 2 ) , which
t h e n u n d e rg o e s an i n t e r n a l A r b u s o v - ty p e r e a c t i o n to g i v e th e
p r o d u c t .
l O - R y O(R 0)3? + O g H - f ^ C H O ^ (RO)gP-----C H - / ' ^ N O
'4 I ~ ( 222)
(RO)
( 223 )
-151-
S i m i l a r r e a c t i o n s t a k e p l a c e w i th a l i p h a t i c187
a l d e h y d e s u n d e r v i g o r o u s c o n d i t i o n s .
A m in o p h o sp h o n i te s have been shown to r e a c t w i t h
a ld e h y d e s a t 100° to g iv e r e a r r a n g e d p r o d u c t s a n a lo g o u s t o
( 219 ) , t h e amino g roup m i g r a t i n g i n p r e f e r e n c e t o t h e 188
a lk o x y .
0 R *20 m in s . |( ((R0)2PNEtg + R'CHO j_QQo > ( R 0 ) 2 P - C H - N E t 3
T h is r e a c t i o n p re s u m a b ly t a k e s p l a c e by a mechanism
a n a l o g o u s t o (217) o r ( 2 1 8 ) .
A m inophosphines have been shown t o u n d e rg o a
s i m i l a r r e a c t i o n w i th a ld e h y d e s . When d i m e t h y la m i n o d i p h e n y l -
p h o s p h in e and b e n z a ld e h y d e a r e h e a t e d t o 120°, a v i g o r o u s r e a c t i o ]
t a k e s p l a c e t o g iv e a h i g h l y c r y s t a l l i n e compound vdiich
c o n t a i n s n i t r o g e n and p h o s p h o ru s and a n a l y s e s f o r GgiHggNOP.
Prom i t s N.M.R. s p e c t r u m , which shows a s i n g l e t i n t e g r a t i n g
f o r s i x p r o t o n s a t 7 .6 5 T (-HMOg) and a d o u b l e t (one p r o t o n ;
J p g = 10 c . p . s . ) a t 5 . 7 ^ ( P —OH— ) , and mass s p e c t r u m , which
shows a mass p eak a t m/e =; 335 , and peak s a t m/e = 2 0 l ( P h g § ) ,
m/e = 1 3 4 (P h — CH— NMeg) t h i s compound a p p e a r s t o be
a - d i m e t h y l a m i n o b e n z y ld i p h e n y lp h o s p h in e o x id e ( 2 2 4 ) .
-152-
Pi f "PhsENMeg + PhCHO -> P hgP -C H -H M ea
(224)
T h is r e a c t i o n p r o b a b ly goes th ro u g h th e
i n t e r m e d i a t e b e t a i n e ( 225 ) , which c a n r e a r r a n g e by an
i n t r a m o l e c u l a r m echanism ( 2 2 6 ) , a n a lo g o u s to ( 2 1 7 ) , o r an
i n t e r m o l e c u l a r mechanism ( 2 2 7 ) , a n a lo g o u s to ( 2 1 8 ) , t o g iv e
th e p r o d u c t .
NIvieg Ph _ NMegA T XPhgP: Ç = 0 PhgP-— CHPh
" 0H
//
k- (225)
Phg _ INMOgMegN-r i - O-r—CHPh PhgP------ CHPh
V . n (2 2 6 ) “7PhHC y 0 A-h P — NMOg
( 2 2 7 ) ^ ^ f\ V
\
0 NMegPhgP-C H Ph
A s i m i l a r r e a c t i o n w i th p a ra fo rm a ld e h y d e gave th e p h o sp h in e
o x id e ( 2 2 8 ) , an a u t h e n t i c sam ple o f w hich was p r e p a r e d by
a iM ann ich type c o n d e n s a t io n be tw een fo rm a ld e h y d e .
-153-
dime th y lam ine and d ip h e n y lp h o s p h in e , and su b s e q u e n t
o x i d a t i o n .
/G H g hPhsENMea + 0"^ ^ 0 -► P h g P - C H g - N M e g
CHg GHg^ 0 '— ( 228)
PhgPH + HCHO + Megim Phg P - CHg “ NMeg
-Ng OgI
8PhgP-C H g-N M eg
An a t te m p t t o e x te n d t h i s r e a c t i o n to
a c r a ld e h y d e gave o n ly p o ly m e r ic s u b s t a n c e s .
D im e th y la m in o d ip h e n y lp h o sp h in e a l s o r e a c t s w i th
ac e to p h e n o n e t o g i v e th e p h o sp h in e o x id e (229) and t e t r a -189
p h e n y lb ip h o s p h in e m onoxide , p re su m ab ly by a b a se
c a t a l y s e d a l d o l c o n d e n s a t io n o f two m o le c u le s o f a ce to p h en o n e
t o g iv e dypnonCy v;hich th e n adds d ip h e n y lp h o s
p h in e o x id e , p ro d u c e d by th e a c t i o n o f w a te r on d im e th y la m in o
d ip h e n y lp h o s p h in e .
8 fPhg PNMeg 4r 2PhC0GH3 Ph - C - GH = G - Ph
0Û
P h g p - t p h g ^ fi ,P h — c — GH— GHPh
Phg PH Me
PhgP= 0 (229)
-154-
W ith c y c lo h e x a n o n e , d im e th y la m in o d ip h e n y lp h o sp h in e
g i v e s t e t r a p h e n y l b ip h o s p h in e m onoxide a s th e o n ly i s o l a t a b l e
p r o d u c t .
B e n z o y ld ip h e n y lp h o sp h in e a l s o r e a c t s w i th a ro m a t i c
a ld e h y d e s , a l th o u g h v ig o r o u s r e a c t i o n c o n d i t i o n s a r e
r e q u i r e d . B en za ldeh yde an d b e n z o y ld ip h e n y lp h o s p h in e gave
b e n z y ld ip h e n y lp h o s p h in e o x id e , w h i le m -c h lo ro b e n z a ld e h y d e
gave m -c h lo ro b e n z y ld ip h e n y lp h o s p h in e o x id e . As y e t th e
mechanism o f t h i s r e a c t i o n h a s n o t been e s t a b l i s h e d .
E x p e r im e n ta l
A l l e x p e r im e n ts u s in g p h o s p h in e s , and s i m i l a r
u n s t a b l e compounds, were c a r r i e d ou t u n d e r an o x y g e n - f r e e
n i t r o g e n a tm o sp h e re . A l l s o l v e n t s were d r i e d b e f o r e u s e .
M e l t in g p o i n t s were u n c o r r e c t e d .
190P r e p a r a t i o n o f D im e th y la m in o d ip h e n y lp h o s p h in e . - A s o l u t i o n
o f dime t h y lam ine (50 g . ) i n e t h e r (250 m l . ) was s t i r r e d and
c o o le d i n an i c e b a th w h i le a s o l u t i o n o f c h lo r o d i p h e n y l
p h o sp h in e (100 g . ) i n e t h e r (150 m l . ) was added d ro p w is e .
A f t e r th e a d d i t i o n th e r e a c t i o n m ix tu r e was a l lo w e d to warm
up to room te m p e r a tu re and s t i r r e d f o r 1 h r . The amine
-155-
h y d r o c h l o r i d e was f i l t e r e d o f f , th e s o l u t i o n e v a p o r a te d
and th e r e s i d u e d i s t i l l e d ( 1 3 0 -1 3 2 ° /0 .9 mm.) to g iv e
d im e th y la m in o d ip h e n y lp h o sp h in e (80 g . ) .
R e a c t i o n o f D im e th y la m in o d ip h e n y lp h o sp h in e w i th B e n z a ld e h y d e . -
The p h o sp h in e ( 9 .5 g . ) and b e n z a ld e h y d e ( 4 . 5 g . ) were h e a t e d
t o g e t h e r a t 140° f o r 3 h r s . The r e a c t i o n m ix tu r e was c o o le d
to g iv e a s o l i d w h ich was shown to be a -d im e th y la m in o b e n z y l -
d ip h e n y lp h o s p h in e o x id e (10 g . ) m .p . ( e t h y l a c e t a t e ) 195-196°
(Found: C, 7 5 .3 5 ; H, 6 .5 5 ; F , 4 .0 4 ; C a lc , f o r CgiHggNOP:
0 , 7 5 .6 ; 6 .5 7 ; P , 4 . 1 8 ) .
R e a c t i o n o f D im e th y la m in o d ip h e n y lp h o s p h in e w i th P a ra fo rm
a ld e h y d e . - The p h o sp h in e ( 7 .3 g . ) and p a ra fo rm a ld e h y d e (,1.2 g .
were h e a t e d t o g e t h e r a t 120° f o r 2 h o u r s , a f t e r w hich th e
r e a c t i o n m ix tu re was s o l i d . R e c r y s t a l l i s a t i o n gave
dime thyaminome th y ld ip h e n y Ip h o s p h in e o x i de ( 4 .9 g . ) , m .p .
( e t h y l a c e t a t e ) 184-185° (Found: C, 6 9 .4 1 ; H, 6 .7 9 ; P , 5 .6 4 ;
C a lc , f o r CiaRj^sNOP: C, 6 9 .5 ; H, 6 .9 5 ; P , 5 . 4 0 ) .
P r e p a r a t i o n o f D im e th y la m in o m e th y ld ip h e n y Ip h o sp h in e o x i d e . -
A m ix tu r e o f d im e th y la m in e (30 g . ) and aq u eo u s fo rm a ld e h y d e
—156-
s o l u t i o n (37%l 60 g . ) w a s s t i r r e d f o r 2 m i n s * D i p h e n y l
p h o s p h i n e ( 1 5 g . ) w a s a d d e d d r o p w i s e a n d t h e m i x t u r e
s t i r r e d a t r o o m t e m p e r a t u r e o v e r n i g h t . H y d r o g e n p e r o x i d e
(15 m l ; 20 v o l . ) w a s a d d e d s l o w l y . T h e s o l i d w a s f i l t e r e d
o f f t o g i v e d i m e t h y l a m i n o m e t h y l d i p h e n y I p h o s p h i n e o x i d e
( 1 5 .5 g . ) m . p . a n d m i x e d m . p . ( e t h y l a c e t a t e ) 1 8 4 - 1 8 5 ° .
R e a c t i o n o f D i m e t h y l a m i n o d i p h e n y l p h o s p h i n e w i t h
C y c l o h e x a n o n e . - T h e p h o s p h i n e ( 4 .3 g . ) a n d c y c l o h e x a n o n e
( 1 .2 5 g . ) w e r e h e a t e d t o g e t h e r a t 140° f o r 12 h r s . T r i t u r a t i o n
o f t h e r e a c t i o n m i x t u r e w i t h l i g h t p e t r o l e u m ( 6 0 - 8 0 ° b . p . )
g a v e t e t r a p h e n y l b i p h o s p h i n e m o n o x i d e ( 2 . 4 g . ) m . p . ( a c e t o n e -
e t h e r ) l 6 6 - l6 7 ° ( l i t . ^ ^ ^ 1 6 7 ° ) .
19 2R e a c t i o n o f B e n z o y l d i p h e n y l p h o s p h i n e w i t h B e n z a l d e h y d e . -
B e n z o y l d i p h e n y l p h o s p h i n e ( 1 .7 g . ) a n d b e n z a l d e h y d e ( 1 . 2 g . )
w e r e h e a t e d t o g e t h e r a t 190° f o r 14 h r s . On c o o l i n g t h e
r e a c t i o n m i x t u r e c r y s t a l l i s e d t o g i v e b e n z y l d i p h e n y l p h o s p h i n e
o x i d e ( 0 .8 5 g . ) , m . p . a n d m i x e d m . p . ( e t h y l a c e t a t e ) 1 9 5 -1 9 6 ° .
A s i m i l a r r e a c t i o n w i t h b e n z o y l d i p h e n y l p h o s p h i n e
a n d m - c h l o r o b e n z a l d e h y d e g a v e m - c h l o r o b e n z y l d i p h e n y I p h o s p h i n e
o x i d e ( 42^ ) m . p . a n d m i x e d m . p . ( e t h y l a c e t a t e ) l 6 2 - l 6 3 ° .
-157 -
1.
2
3
*
5
6
7
8
g
10
R e f e r e n c e s
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-159 -
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620
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45
46
47
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