C A T A L Y T I C T R A N S F O R M A T I O N S O F F U R A N

A N D K E T O N E S A N D T H E I R D E R I V A T I V E S

COMMUNICATION 2. SOME TRANSFORMATIONS -

O F 3- (2- FURY L)A LKYL A CETAT ES

N. I . S h u i k i n , R. A. K a r a k h a n o v , a n d I . I b r a k h i m o v

A L C O H O L S

UDC 542.97+547.45

The investigation of the catalytic t ransformat ions of furan alcohols presents considerable in teres t , because it opens up new methods for the synthesis of such difficultly access ib le compounds as y -ke to a lco- hols and their ace ta tes , 2 ,3-dihydrofuran homologs, and furan itself. The method of synthesizing these compounds is based on the catalytic hydrogenation not of the furan alcohols themselves , but of their acetates , which makes it possible to retain a "protected" hydroxy group in the side chain. The acetates of y -ke to alcohols obtained in this way a re readily converted into y -ke to alcohols and mono- and di-substi tuted 2,3- dihydrofuran homologs [1]. On dehydrogenation over platinized charcoal the latter give good yields of all- substituted furan homologs [2].

The experimental data obtained in the present investigation provide answers to two questions: how does the hydrogenation of 3-(2-furyl)alkyl acetates proceed over a skeletal n icke l -a luminum catalyst , and how does the hydrogenolysis of acetates of secondary furan alcohols, such as a -methy l -2 - fu ranpropano l , proceed over platinized charcoal. It has been shown previously [3] that the furan r ing is able to undergo so-ca l led "conjugated" hydrogenolysis in vapor -phase hydrogenation over a skeletal Ni-A1 catalyst. In this case the furan r ing opens in three directions at bonds 1,5 (1), 1,5 and 4,5 (2), and 1,5 and 3,4 (3), as a resul t of which butyryl , propionyl, and acetyl groups are formed

1,5 ~* C--C~C--C--R (1)

4',a 1 ]] - ~ - ~ 2 1~ Cleavage ,5 and 4 5 0 �9 'C--C--C--R

, ' ~ 0 ~ ' ~ - of bonds \ II (2) 1 ~-,5 and3 ,4 0

II O

in which R =alkyl, hydroxyalkyl, or carboxyalkyl.

By the method of "conjugated" hydrogenolysis a whole ser ies of te t rahydrofuran homologs [4], y - d i - ketones [5], and y - k e t o carboxylic es te r s [6] have been obtained from various furan compounds. In view of this it was considered to be of in teres t to investigate the hydrogenation of 3-(2-furyl)alkyl acetates over a skeletal Ni-A1 catalyst under "conjugated" hydrogenolysis conditions. We have shown previously [1] that t:m hydrogenation of 2-a lkyl -3-(2-furyl )propyl acetates over P t - C at 200-220 ~ leads to the formation of two products: the acetate of the corresponding y -ke to alcohol and the aliphatic ketone formed as a resu l t of the side react ion in which the acetoxy group is eliminated as acet ic acid.

C--C--C--C--C--C--C + C--C--C--C--C--C--C + c--c--~ 220 o II I II o -~-COCH~ 0 OCOCH~ O

4- CH3COOH

in which R = H, CHa, C2H s

As would be expected, in the hydrogenation of 3-(2-furyl)propyl acetates over a skeletal Ni-A1 catalyst acetic es te r s of y -ke to alcohols and aliphatic ketones are also formed. However, unlike the behavior over platinized charcoal , over the Ni-A1 catalyst "conjugated" hydrogenolysis occurs and the elimination of ace- toxy groups goes in higher yield than over P t - C . All this leads to the formation of quite a number of

N. D. Zelinskii Institute of Organic Chemist ry , Academy of Sciences of the USSR. Transla ted from Izvest iya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 10, pp. 1807-1810, October, 1966. Original ar t ic le submitted May 15, 1964.

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I

5Q

o

,q

> 0 r.~

0

r

I 0-1

I

�9

�9

b~ �9

N

r162 o

I

m

cL~

g~

~llco

l l g ~ -

d d d 2 d d d g d d d d d d

I 1 � 9 f i l l I l l t

O L O t r 3 0 I LO O C ) O 0 0 0 C ~ O 0 0 L O

I

~ oo 0 ~ 0 ~ c d 0

0 ~ o ~ C q ~

~ o o ~.~

~ , , , ~ f ~ 0 0 ;>.. ;>., ;:: ~ ~ , ~ ~ . ~ 0 ~ ~ ~ - ~ o ~

~ _ ~ n ~ : ~ N N N ~ r ~ o ~ m o o

f I I

r f2~

c~ ~ v ~ o

aliphatic ketones and acet ic e s te r s of y - k e t o alcohols. The resul ts of the experiments are presented in Table 1.

The answer to the second of the questions posed above is given by the investigation of the vapor -phase hy- drogenation of 3- (2-furyI)- 1-methylpropyl acetate over P t - C at ordinary p r e s s u r e and 240-250 ~ I t was found that under these conditions 3- (2-furyl)- 1-methylpropyl acetate undergoes complex changes, the final products of which a re acet ic acid (I), 2-octanone (II), 4-octanone (III), 2-butyl te t rahydrofuran (IV), and t e t r ahyd ro -2 -me thy l -5 - propylfuran (V). Here again one of the possible courses of react ion is the elimination of the acetoxy group in the form of acet ic acid and the formation of an aliphatic ke- tone (4-octanone) af ter the hydrogenolysis of the in te rme- diately formed 2-butylfuran (VI), of which a smal l par t is hydrogenated to 2-butyl te t rahydrofuran (IV). Another course of react ion appears to be the reduct ion of the acet ic e s t e r taken to ~ -methy l -2 - fu ranpropano l (VII), the fur ther hydrogenation of which leads to the formation of te t rahydro- 2 -methy l -5 -propy l fu ran and the ketones (II) and (III) (see react ion scheme).

Reaction Scheme

0 C O C t t s ( V I )

J (IV) 0 (iii)

OH 0ti j

- - H 2 0

r - - - " C - - ( ] - - q - - c - c - - ~ ; - - q - - ( ', ( i I)

c : - - c - C - L o / l - - c - - ; ~

(v) L - - ~ c--c--c--c--(:--c--c--( (III) IT o

EXPERMENTAL

2-Furanpropanols were synthesized in accordance with the scheme described by us previously [1,7]:

R NaOH ~ ) ! t ie, Cu--AI )--CHO + t:tCH~CR'--~2~ --CI[=(--C--n'

II 0 F[ 120 arm, 150" 0 O 0

R r

1 OH

in which R ' = H , R = H , C2H5; R '=CHa, R=H. 3- (2- Furyl) alkyl acetates were prepared by heating the furan alcohols with excess of acetic anhydride and f reshly fused sodium acetate taken in an amount of 10% on the weight of the acet ic anhydride. The mixture was boiled for 2 h and then

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cooled to 40-500 , wate r (ten t imes the amount of acet ic anhydride taken) was added, and the mixture was left for 3 h. The acetylat ion product was ex t rac ted with e ther , dr ied over fused Na2SO4, and vacuum-dis - tilled. We obtained: 1) 3 - (2-Fury l )propyl acetate; b.p. 100.7-101.5 ~ (12 ram); riD2~ 1.4562; d42~ 1.0449. 2) 2 -Ethyl -3- (2- fury l )propyl acetate; b.p. 98-99.5 ~ (8 ram); nD 2~ 1.4595; d~ ~ 1.0172. 3) 3- (2- F u r y l ) - l - m e t h y l - propyl acetate; b.p. 110-112 ~ (20 ram); nD2~ 1.4578; d ~ 1.0318.

The prepara t ion of the P t - C and skeletal Ni-A1 catalysts and the exper imenta l conditions have been descr ibed e a r l i e r [1, 6]. The catalyzates were analyzed by means of gas- l iqu id chromatography. Standard samples were available for most of the compounds. The chromatographic apparatus and the conditions used in the chromatography a re descr ibed in our previous paper [8]. The exper imenta l resu l t s a re presented in Table 1.

C O N C L U S I O N S

I . F .

N. I . N . I . I . F . NoI. 750. I . F . I . F .

1. A study was made of the conjugated hydrogenolysis of 1-(2-furyl)propyl aceta tes over a skeletal Ni-AI catalyst at 240-250 ~ The furan ring undergoes cleavage in th ree di rect ions , and as a resu l t aliphatic ketones and acet ic e s t e r s of 7 -ke to alcohols a re formed.

2. The vapor -phase hydrogenolysis of secondary 3-(2-furyl)a lkyl aceta tes was investigated over P t - C at normal p r e s s u r e and 240-250% Under these conditions the final products of the hydrogenation of 3- (2-furyl)alkyl aceta tes a re te t rahydrofuran homologs and aliphatic ketones.

L I T E R A T U R E C I T E D

1. Bel ' sk i i , N. I Shuikin, and R. A. Karakhanov, Izv. AN SSSR, Ser. khim., 1964, 326. 2. Shuikin, I. F. Bel ' sk i i , and R. A. Karakhanov, Dokl. AN SSSR, 147, 119 (196~.). 3. Shuikin, V. A. Tulupov, and I. F. Bel ' sk i i , Zh. obshch, khimii, 25, 1175 (1955). 4. Bel ' sk i i , Izv. AN SSSR, Otd. khim. n. , 1962, 142. 5. Shuikin, I. F. Bel ' sk i i , R. A. Karakhanov, and A. A. Nazaryan, Izv. AN SSSR, Set . khim., 1964,

6 .

7. 8.

Bel ' sk i i , N. I. Shuikin, and V. M. Shostakovskii, Dokl. AN SSSR, 152,862 (1963). Bel ' ski i and R. A. Karakhanov, Izv. AN SSSR, Otd. khim. n., 1962, 905.

N. I. Shuikin, R. A. Karakhanov, V. G. Glukhovtsev, and I. Ibrakhimov, Izv. AN SSSR, Set . khim., 1966, 182.

All abbrev ia t ions of per iodica ls in the above bibl iography are le t ter-by-let ter t rans l i te ra- t ions of the abbrev ia t ions as g iven in the original R u s s i a n journal. Some or aIl of th is per i -

od ica l l i tera ture m a y w e l l be a v a i l a b l e in E n g l i s h t rans la t ion . A complete l i s t of the cover-to- cover Eng l i sh t rans la t ions appears at the back of the f i rs t i s s u e of this year.

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