148

CHAPTER 3

NITROGEN HETEROCYCLES FROM DIBENZOYL ETHYLENE AND ITS DERIVATIVES

3.1 Introduction

ham-Dibenzoyl ethylene or Q-1,4-diphenyl-2-buten-1,4-dione is a readily

available solid formed by the Friedel-Crafts acylation of benzene and fumruyl chloride.'

This compound as well as its derivatives has been extensively employed for the

generation of several carbocyclic and heterocyclic compounds.2 Due to the presence of

two electron withdrawing benzoyl groups, dibenzoyl ethylene and its derivatives are

good as dienophiles, and they have been used in Diels-Alder and other cycloaddition

reaction^.^ In the foregoing, a brief overview of the recent literature in which dibenzoyl

ethylene and their derivatives were converted to carbocycles and heterocycles is

presented. A glance of the literature reveals the versatility of dibenzoyl ethylene for the

generation of several interesting compounds.

3.1.1 Synthesis of Carbocycles from Dibenzoyl Ethylene and its Derivatives!

Differently substituted Wittig salts such as 2 react with dibenzoyl ethylene 1

under a variety of conditions to furnish cyclopentenone 3 in a highly diastereoselective

fashion (Scheme 3 . 1 ) ~ ~ '

1 2 3

Reagents andconditions: i. BuLi, THF, -78 C; ii. CH&OOH, aq. NaHCO,, 30°C

Scheme 3.1

The synthesis of a series of highly substituted cyclohexanol derivatives such as 5

has been carried out in a single pot reaction of acetophenones 4 and dibenzoyl ethylene

149

1 in the presence sodium ethoxide as base. Formation of this product is expected to go

through double Michael addition followed by aldol condensation (Scheme 3.2 ).'

Reagents and conditions: i. NaOEt, ether, rt.

Scheme 3.2

Dibenzoyl ethylene reacts with reactive dienes to form interesting carbocycles.

For example a tandem double Diels-Alder reaction of a-quinodimethane 6 with two

moles of dibenzoyl ethylene 1 results in the formation of the adduct 7 (Scheme 3.3);

which served as an intermediate for the preparation of novel thiophene and pyrrole

analogs of trypticene.

p h + ph

o W r z &oph coph coph

1 6 Reagents and conditions: i. NaI, acetone, reflux.

Scheme 3.3

3.1.2 Synthesis of Heterocycles from Dibenzoyl Ethylene and its Derivatives

Dibenzoyl ethylene has been reported to undergo facile cycloaddition reactions

with reactive species leading to formation of several heterocyclic compounds. The

generation of aminocarbene 9 from N,N-dimethylaminobenzotriazolylmethylenim

chloride 8 and trapping in a [1+4] cycloaddition with dibenzoyl ethylene 1 has been

reported (Scheme 3.4).1°

8 9 1

Reagents and conditions: i. NEt,, benzene, reflux.

Scheme 3.4

The furan ring is found in many natural products and several derivatives of fura~

have immense industrial applications. An important method for the preparation of furaI

is the acid catalysed cyclisation of 1,4-dicarbonyl compounds. Under acidic conditions

substituted reduction product of dibenzoyl ethylenes 1 undergo dehydration to result in

the formation of subsituted b a n s 11 (Scheme 3.5)." This reaction is facilitated by the

presence of electron donating groups.

Reagents and conditions: i. p-TsOH, C6H6, reflux.

Scheme 3.5

Condensation of arylacetonitrile 12 and dibenzoyl ethylene 1 in basic condition:

results in the formation of novel bicyclo [2.2.2] lactones 13 (Scheme 3.6).12

Reagents and conditions: i. NaOEt, ether, rt.

Scheme 3.6

Several cage compounds have also been synthesised starting from dibenzoyl

ethylene.14 l 5 The Diels-Alder adduct 14 and 16 formed from dibenzoyl ethylene 1 with

furan or cyclohexadiene has been converted to tetraacetal oxacages and convex

oxacages such as 15 and 17 through ozonalysis and cyclization reaction (Scheme 3.7).

p h y J T h 0 hmPh & $+b" COPh Ph

I iii & COPh 0

Reagents and conditions: i. Furan, benzene, reflux; ii. O>/Me*S; iii. Cyclohexadiene, benzene, reflux.

Scheme 3.7

Dibenzoyl ethylene 1 reacts with enamines 18 in an interesting fashion to result

in the formation of oxa-cage compounds 19 (Scheme 3.8). This reaction may go

Mor Morpholino

Reagents and conditions: i. MeOH, rt.

Scheme 3.8

I52

through ene reaction followed by [2+2+2] cycloaddition of two carbonyl groups to the

enamine double bond."

An interesting dehydrative transformation of 1-alkyl-3,4-diaroylpyrrolidines 20,

which are readily accessible via the condensation of dibenzoyl ethylene 1,

paraformaldehyde and amino acid, into I-alkyl-2-aryl-3methyl pyrroles 21 has been

reported (Scheme 3.9).16

Reagents and conditions: i. RNHCH2COOH, (CHzO)., toluene, reflux; ii. Ethylene glycol, 1 30°C.

Scheme 3.9

C2 symmetric chiral mines 24 of high enantiomeric purity, which are useful

reagents for asymmetric synthesis, have been prepared from dibenzoyl ethylene 1 in

Reagents and conditions: i. SnCI2/HCI; ii. Ipc2BC1, THF, -78OC-rt; iii. MsCI, Et3N, CH2Ch -2ODC; iv. CH~XCHCH~NH~, EtyN, O°C+rt; v. (PhlP)3RhCI, H20, CHjCN, reflux.

Scheme 3.10

four steps (Scheme 3.10)." A key step in the reaction sequence is the asymmetric

reduction with Ipc2BCl of dione derived from 1.

The cycloadducts 26 derived by the addition of N-p-tosyl pyrrole 25 to

dibenzoyl ethylene 1, on treatment with sodium borohydride followed by nickel

chloride resulted in the formation of 2,3-bis(methy1ene)-N-p-tosyl-7-

aZabicyclo[2.2.1]hept-5-ene 27 (Scheme 3.1 I).''

Reagents andconditions: i. BFj.Et20, benzene, 50°C; ii. NiCg N a b , EtOH.

Scheme 3.11

Several quinoline derivatives have been synthesised starting from dibenzoyl

ethylene and its derivatives via Diels-Alder reaction pathways. For example, Diels-

Alder reaction of N-sulfonyl substituted aza-o-quinodimethane 28 resulted in the

formation of tetrahydroquinoline derivative 29 (Scheme 3. 12).19

Reagents and conditions: i. Toluene, reflux.

Scheme 3.12

Reagents and conditions: i. NaOH, rt

Scheme 3.13 On the other hand, condensation of dibenzoyl ethylene with cyanoacetophenone

30 resulted in pyridine derivative 31 (Scheme 3.1 3)."

Pyridazine 33,2'** and pyrazoline 3223 derivatives has been obtained by the

condensation of dibenzoyl ethylene with diazomethane and phenyl azide respectively

(Scheme 3.14).

R

32 1 33

Reagents and conditions: i. PhNHNHz.HCI, gl. Acetic acid, 110C; ii. Azide, EtOH, 80°C.

Scheme 3.14

Condensation of dibenzoyl ethylene 1 with C-(2-nitro)-styryl-N-phenyl nitrone

34 resulted in a regiospecific and stereospecific synthesis of isoxazolidine derivative 35

(Scheme 3.1 s)."

Reagents and conditions: i. NaOM, EtOH

Scheme 3.15

Several bioactive heterocycles incoporating two or more heteroatoms have been

prepared from dibenzoyl ethylene 1 using 1,3-dipolar cycloaddition ~trategy.~'.~' For

example thiadiazoles 37 has been obtained by the reaction of dibenzoyl ethylene 1 with

trithiazyl chloride 36 (Scheme 3.16)

F' r4.n

~ h y J P h + a,.%Ns.c, I, p h O = H - N N 's'

0

Reagents and conditions: i. CCI4, N2, reflux.

Scheme 3.16

155

Thus, it is clear from the literature that dibenzoyl ethylene served as a versatile

precursor to both carbocyclic and heterocyclic compounds. Driven by the fact that we

isolated novel bicyclic and spirocyclic systems by simple reaction of cyclopentanone to

chalcone and phenyl vinyl ketone we tried such reactions on dibenzoyl ethylene also.

Results obtained in this study and further elaboration of the products to

teeahydroquinoline derivatives forms the basis for this chapter.

3.2 Results and Discussion

Dibenzoyl ethylene is commercially available but expensive.28 Literature search

for its preparation revealed that Friedel-Crafts acylation of benzene and its derivatives

using fumaryl chloride is a convenient method for the synthesis.' However generation

of fumaryl chloride from fumaric acid and phthaloyl chloridez9 requires stringent

conditions. Therefore, we explored alternative methods for generation of fumaryl

Reagents and conditions: i. Reflux, 0.5h.

Scheme 3.17

chloride from fumaric acid, which included treatment with thionyl chloride,

phosphorous oxychloride, phosphorous trichloride, phosphorous pentachloride and

benzoyl chloride. We found &at employing phoshorous pentachloride 39 in 1 : 1.1

stoichiometric ratio of fumaric acid 38, at reflux temperature followed by distilling off

POCI, formed in the reaction, followed by fumaryl chloride (bp 161-164 'C) is a

convenient method for the generation of this acid halide (Scheme 3.17). The furnary1

chloride 40 was used for further reaction with benzene and its derivatives such as 41-43

to yield dibenzoyl ethylene 1 and its derivatives 45 and 46 (Scheme 3.18). Yield in this

reaction was found to be generally good and comparable to literature procedure.'

Reagents and conditions: i. AIC13, rt, 2h; ii. AICl,, CS2, 50°C, 3h.

Scheme 3.18

Dibenzoyl ethylene 1 was subjected to Michael addition with the anion

generated from cyclopentanone 47 in presence of barium hydroxide with the intention

of studying the formation of carbocyclic products as we found in the case of chalcone

and phenyl vinyl ketone. However from this reaction we could isolate only the

corresponding triketone 48 (Scheme 3.19). We attempted Michael addition under a

variety of conditions such as NaOEtEtOH, NaOEtIether, KOWMeOH and

NaOWEtOH. In none of the cases we could isolate any other product other than the

diastereomeric mixture of triketones 48

Reagents and conditions: i. Ba(OH)z, EtOH, rt, 12h.

Scheme 3.19

The structure of the triketone 48 was secured on the basis of IR, 'H and "C

NMR spectra. The IR spectrum showed the cyclopentanone carbonyl absorption at

1730 cm" and aromatic ketone stretching at 1670 cm-'. 'H NMR (Fig. 3.1) revealed the

157

presence of aromatic and aliphatic protons in the ratio of 1 : 1. Tertiary hydrogen next to

aromatic ketone appeared most downfield in the aliphatic region at 6 4.6 ppm as

multiplet. In the aromatic region a set of four broad doublets accounting for four

protons vicinal to aromatic keto groups were clearly discernible. "C NMR spectrum

(Fig. 3.2) revealed two sets of 17 lines indicating that the sample is a diastereomeric

mixture with one of the isomers being major (60%).

X = Me; 49 X = CI; 50

X = Me; 51 X=CI; 52

Reagents and conditions: i. Ba(OH)z, EtOH, rt, 12h.

Scheme 3.20

The other substituted dibenzoyl ethylene employed for this study namely 4,4'-

dimethyl 49 and 4,4'dichlorodibenzoyl ethylene 50 also did not reveal the formation of

any other product other than the triketone 5152 (Scheme 3.20). The spectral data (Fig.

3.3-3.6) of these compounds also matched well with the unsubstituted case

Many pyridine derivatives show impressive physiological activity and are

Present as structural moieties in several alkaloids. Keeping this in view, the triketones

48, 51, 52 were converted to hitherto unreported 2-phenyl-4-

benzoyl~~clo~enta[b]~~ridine derivatives. This oxidative amination reaction was

expected to reveal the reactivity of the triketone. If cyclopentanone and aromatic ketone

moieties react as 1,5-diketone, pyridine ring would be formed. On the other hand,

160

reaction of either cyclopentanone and aromatic ketone or two aromatic ketones react as

1,4-diketones, pymle ring formation would take place (Scheme 3.21).

54 48 55

Scheme 3.21

To test the above possibilities, triketone 48 was treated with ammonium acetate

in presence of methanol for two days (Scheme 3.22). A relatively non-polar product

with high Rr value was found in the reaction in about 15% yield, as a white powder (mp

134 OC ). Analysis as well as mass spectroscopy revealed the molecular formula to be

C21H17NO. The IR spectrum showed the presence of aromatic carbonyl group

stretching frequency at 1650 cm". The 'H NMR spectrum (Fig. 3.7) showed the

presence of aromatic and aliphatic protons in the ratio of 1.8:l. The aromatic CI-H

appeared as a singlet at 8 7.4 ppm. The two vicinal hydrogens to aromatic ketone

appeared as doublet at 6 7.93 ppm. Cs-H and C,-H appeared as triplet in the aliphatic

region at 6 2.95 and 3.14 ppm respectively. Presence of aromatic keto group and three

methylenes in the 'H NMR spectrum ruled out the possibility of formation of pyrrole

derivatives 54 and 55 (Scheme 3.21).

Fig. 3 5 'H NMR Spectrum of i .4-di(4-chlorophenyl)-2-(2-0xocydopmtyl)-1.4- butanedione (52)

48 53

Reagents and conditions: i. NH40ac, MeOH, a, 48h.

Scheme 3.22

The "C NMR spectrum (Fig. 3.8) showed seventeen signals in which only three

were in the aliphatic region. The carbonyl carbon was observed at 6 195.7 ppm. The

X = Me; 51 X=CI; 52

X = Me; 54 X = C1; 55

Reagents and conditions: i. NhOAc, MeOH, a, 48h.

Scheme 3.23

DEPT spectrum (Fig. 3.9) highlighted the presence of CI-H. Based upon the above

Spectruscopic and analytical data the structure of the cyclopenta[b]pyridine derivative

was confirmed as 53

The triketones 51 and 52 were converted to cyclopenta[b]pyridine derivatives

56. 57 under similar reaction conditions and the spectral characteristics (Fig. 3.10-3.13)

wem found to be similar to that of the unsubstituted case (Scheme 3.23). Admittedly

the yields in these reactions is very low (10-20 %). Several variation in the reaction

- - Fig. 3.13 "C NMR Spectrum of4-chloromethy~~henyl-2-(4-

chloromethylphenyl)-6,74ihydro-5H-cyclopenta[h]pdin-ymone (57)

1731

conditions were attempted to increase the yield, which include conducting reactions

with excess ammonium acetate or ammonium bromide in different solvents such as

methanol, ethanol, glacial acetic acid. However, all attempts were proved to be futile.

Thus we have synthesised Cbenzoyl cyclopenta[b]pyridine derivatives through a

simple two step reaction sequence.

3.3 Experimental Section

Preparation of dibeozoyl ethylene

Fumaric acid (1.25g, I0 mmol) and PCls (2.298, 1 1 mmol) was taken in a 25 mL

round bottomed flask fined with a condensor and CaCI, guard tube and reflux heated at

120UC for 0.5 h. The reaction mixture was then distilled and the first fraction which

distilled at -105'C was discarded and the second fraction which distilled at -160°C was

collected. This was then immediately used for the preparation of dibenzoyl ethylene by

the reported method.' To a mixture of aluminium chloride (2.66 g, 13.3 mmol) and

benzene (14.86 g, 233.3 mmol) was added fumaryl chloride (I .5g, 10 mmol) dropwise

over a period of 30 min. with stirring. The stirring was continued for a period of 1 h at

rt and the reaction mixture was then poured onto crushed ice containing con. HCI

(1mL). The organic layer was separated and washed with saturated sodium bicarbonate

(2 x 15 mL),brine ( 2x 10 mL), dried (anhyd. Na~S04) and concentrated to give

dibenzoyl ethylene

1.4-Diphenyl-2-buten-1,4-dione (1). Yield 70%. mp 106 OC. 'H NMR (300, MHz,

CDCI,) S 8.02 (d, J = 7 Hz, ZH), 7.96 (s, IH), 7.44-7.59 (m, 3H). "C NMR (75 MHz,

CDCI,) 6 189.2(Cl), 137.1(CI,), 135.2(Cr). 135.6(Cj,), 128.9(C~).

1,4-Di(4-methylphenyl)-2-buten-1,4-dione (49). Yield 71%. mp 150 OC. IH NMR

(300, MHz, CDCI,) S 7.93 (d, J = 5 Hz, 2H), 7.90 (s, IH), 7.25 (d, J = 18 Hz, 2H),

1,4-Di(4-chlorophenyI)-2-buten-1,4-dione (50). Yield 45%. mp 170 OC. I H NMR

(300, MHz, CDCl3) 8 7.99 (dd, J = 7, 2 Hz, 2H), 7.97 (s, lH), 7.51 (dd, .J= 7,2 HZ, 2H).

I3c NMR (75 MHz, CDCI3) 8 188.3(C1), 140.6(C1,), 135.0(C4.), 134.8(C2), 130.2(C2),

129.2(C3,).

Reaction of dibenzoyl ethylene with cyclopentanone under basic conditions,

general procedure

To a stirred suspension of freshly activated Ba(OH)* (heated to 100°C for 2h and

cooled in a desicator, 0.1713g, I mmol) in 5mL of absolute alcohol, cyclopentanone

(0.462g. 5.5 mmol) was added dropwise at room temperature and stirred for 10 min.

Dihenzoyl ethylene (1. 18g, 5 mmol) was added drop wise to the reaction mixture and

stirred for 12 h at room temperature. TLC of the reaction revealed the presence of one

major product (Silica plate, hexane:ethyl acetate 95:5, double run. The reaction mixture

was diluted with dichloromethane, washed wth ice water (2 x 10 ml), brine (2 x 10

mL), dried (NazSOd) and concentrated . The crude product was passed through column

chromatography using silica gel (100-200 mesh) with hexanelethylacetate solutions as

eluent (99:l to 90:lO) to give 48.

1,4-Di(phenyl)-2-(2-oxocyclopentyl)-1,4-butanedione (48). RF = 0.4. Yield = 53%.

mp = 66 OC. IR (KBr) v 3020,2397, 1730, 1680, 1597, 1450, 1402, 1217, 1157, 1001,

833, 742,690 cm". 'H NMR (200 MHz, CDC13) 6 8.05 (d, J = 6 Hz, 2H), 7.92 (d, J = 9

Hz, 2H), 7.43-7.48 (m, 3H), 7.38 (dd, J = 10, 5 Hz, 3H), 4.62-4.65 (m, IH), 3.61 (dd,

= 12. 8 Hz, IH), 3.17 (dd, J = 12, 4 Hz, IH), 2.30-2.50 (m, lH), 1.90-2.10 (m, 2H),

1.50-1.80 (m, 4H). I3c NMR (50 MHz, CDCI3) 6 219.9(C~), 197.8(C1), 196.9(C4),

144.2(CI.-), 143.9(Cl-), 129.9(C2...), 129.3(C2,,), 128.6(C~), 127.4(C~), 127.2(C4,,),

-. 175

126.9(Cr.-), 49.7(Ct8), 42.3(C2), 41.l(C3), 39.3(C~), 26.2(Cy), 20.9(C4,). HRMS (M3

m/z cdcd. for C ~ I H Z O ~ 320.386 obsd. 320.304.

1,4-Di(4-methylphenyl)-2-(2-0xoey~1openty1)-1,4-butanedioe (51). Rr= 0.38. Yield

= 47%. Gel like substance. IR (neat) v 3019, 2401, 1729, 1689, 1608, 1447, 1407,

1219, 1004, 930, 762, 675 cm". 'H NMR (200 MHz, CDCI,) S 8.04 (dd, J = 5, 1 Hz,

2H), 7.94 (dd, J = 5.2.5 Hz, 2H), 7.46-7.50 (m, 2H), 7.24 (dd, J = 10, 5 Hz, 2H), 4.63-

4.68 (m, lH), 3.59 (dd, J = 11, 9 Hz, lH), 3.18 (dd, J = 11, 3 Hz, lH), 2.40-2.60 (m,

lH), 2.39(s, 3H), 2.37(s, 3H), 2.00-2.20 (m, 2H), 1.60-1.90 (m, 4H). I3c NMR (50

MHz, CDC13) 8 218.O(Cz,), 197.9(C1), 197.7(C4), 144.1(C1,,), 144.0(CI*,,), 137.3(C4.-),

136.5(C4..), 129.4(C3*.), 129.2(C3-), 128.5(C2,-), 128.0(C2-), 49.8(C1.), 41.1(c2),

40.9(C3), 38.3(C3.), 26.1(C,,), 21.6(C4,), 20.6(C1,), 20.5(C1.,,.). HRMS (M') mlz calcd.

for C23H2403 348.440 obsd. 348.398

1,4-Di(4-cblorophenyI)-2-(2-oxoeycIopen~~)-,4-butanedione (52). Rt= 0.42. Yield

= 35%. mp = 67 'C. 1R (KBr) v 3020, 2397, 1730. 1680. 1597, 1450, 1402, 1217,

1157, 1001, 833,742,690 cm". 'H NMR (400 MHz, CDCl3) S 7.99 (dd, J = 8, 4 Hz,

2H), 7.87 (dd, J = 8, 6 Hz, 2H), 7.46 (dd, J = 8, 2 Hz, 2H), 7.41 (dd, J = 9, 2 Hz, 2H),

4.54-4.59 (m, lH), 3.59 (dd, J = 17, 9 HZ, lH), 3.08 (dd, J = 18, 4 Hz, IH), 2.40-2.60

(m, lH), 2.00-2.30 (m, 2H), 1.50-1.90 (m, 4H). I3c NMR (100 MHz, CDCL) 6

218.2(C2.), 196.9(C4), 196.2(Cl), 139.9(Cl,.), 139.6(Cl,,), 135.6(C4-,), 134.6(Cd.,),

130.1(C2...), 129.4(C3,,), 129.2(Ca.), 128.6(Cy), 50 ~(CI.), 41.2(C2), 40.7(C~), 38.1(C3.),

25.9(C~), 20.5(C~). HRMS (M+) ndz calcd. for C21H~sC1203 389.276 obsd. 389.234.

General procedure for the formation of cyclopenta[blpyridine derivatives from

triketones

The triketone 48 (0.225 g, 0.7 mmol), dissolved in dry methanol (5 mL), ammonium

acetate (0.539g, 7 mmol) was added to it and allowed to stir at rt for 48 h. TLC of the

176 1

reaction rcveded the presence of a product dong with starting material. The reaction

mixture was concentrated in vacuo, diluted with dichloromethane (lOmL), washed with

water (2 x 15 mL), brine (2 X 10 mL), dried (anhyd. Na2S04) and concentrated in

vacuo. It was purified by column chromatography with silica (100-200 mesh) using

hexandethyl acetate 98:2 as eluent.

Phenyl-2-pbenyl-6,7-dihydr0-5H-ryc~0pent[blpyd-~lmethanone (53). Yield

= 20%. R f = 0.35. mp = 134 OC. IR (nujol) v 2920, 1650, 1580, 1440, 1370, 1340,

1240, 1190, 1060, 1020, 880, 840, 790, 710, 680 cm-I. 'H NMR (300 MHz,

CDCI31CCL) G 7.93 (d, J = 8 Hz, 2H), 7.82 (d, J = 9 Hz, 2H), 7.42-7.62 (m, 3H), 7.40

(s, 1Hh7.31-7.38 (m, 3H), 3 . 1 4 ( t , J = 8 Hz,2H),2.95 ( t , J= 8Hz,2H),2.15 (q , J=7

HZ, 2H). "C NMR (75 MHz, CDCI3/CCL) 6 195.8(CI-), 167.7(C7,), 156.2(C2),

141.9(c1..), 139.1(C1.), 136.5(C4), 133.7(C4J, 133.4(Cz.,), 129.9(C23), 128.8(Cj*),

128.6(C4..), 126.9(C4.), 1 16.7(C3), 34.3(C7), 30.O(Cs), 23.1 (C6). HRMS (Mt) m/z calcd.

for C21H17NO 299.371 obsd. 299.377.

4-Methylphenyl-2-(4-methylphenyl)-6,7-dihydro-5H-cyclopenta[b]pyridin-4-

ylmethanone (56). Yield = 11%. Rf = 0.32. IR (nujol) v 2910, 2840, 1650, 1590,

1430, 1395, 1365, 1335, 1245, 1170, 1080, 1010, 960, 810, 755 ern.'. 'H NMR (300

MHz, CDCIj/CCI4) 6 7.76 (d, J = 8 Hz, 2H), 7.65 (d, J = 10 Hz, 2H), 7.39 (s, IH), 7.18

( d , J = 8 Hz,2H),7.13 ( d , J = 8 Hz,2H),3 .04(t ,J=8Hz,2H),2 .85(t ,J=8 Hz,2H),

2.08 (q, J = 7 HZ, 2H), 1.26 (s, 3H), 1.21 (s, 3H). "C NMR (75 MHz, CDCl31CC14) 6

195.5(Cl.-), 167.5(C7.), 156.2(C2), 144.3(Cl,,), 142.2(Cl.), 138.5(C4,), 136.4(c4),

134.0(C4-), 133.2(C4,), 130.2(C2.,), 129.3(C3-), 126.8(cj.), 1 16.4(C3), 3 1 .~(CS),

24.3(C,), 23.2(C6), 21.8(CI,,), 21.3(clv). HRMS (M+) m/z calcd. for C Z ~ H ~ I N O 327.425

obsd. 327.409.

177

4 - C h l o r o p h e n y l - 2 - ( 4 - e h l o r o p h e n y 1 ) - 6 , 7 ~ -

ylmethanone (57). Yield = 9%. Rr= 0.30. IR (nujol) v 2920,2840, 1655, 1580, 1455,

1370, 1240, 1080,1000,850 cm-'. 'H NMR (300 MHz, CDC13/CC4) 6 8.01 (d, J = 8

Hz, 2H), 7.86 (d, J = 8 Hz, 2H), 7.57 (d, J = 10 Hz, 2H), 7.49 (d, J = 8 Hz, 2H), 7.35 (s,

lH), 3.23 (t, J = 6 Hz, 2H), 3.05 (t, J = 6 Hz, 2H), 2.29 (q, J = 7 Hz, 2H). "C NMR (75

MHz, CDCl&Cb) 6 196.3(C1.-), 168.2(C7&, 155.2(C2), 144.O(C1-,), 141.3(Cj .),

135.1(C4.), 133.8(Cv), 133.2(GJ, 131.4(Cr), 129.2(C3.), 129.O(Cj.s), 128.2(Cr),

116.2(C3), 34.4(C,), 30.2(C~), 23.3(C6). HRMS m/z calcd. for C ~ ~ H I ~ C ~ ~ N O

368.261 obsd. 368.264.

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