Novel domino reactions of (Z,Z)-2,2'-thiobis(1,3-diarylprop-2-en-1-ones) with acetylacetone and ethyl acetoacetate: Stereoselective synthesis of highly functionalized dihydrofurans

Article abstract of DOI:10.1080/00397910802664236

The domino reactions of (Z,Z)-2,2'-thiobis(1,3-diarylprop-2-en-1-ones) with acetylacetone and ethyl acetoacetate in the presence of sodium ethoxide afforded the corresponding 4,5-dihydrofurans stereoselectively in moderate yields presumably via a Michael

Full text of DOI:10.1080/00397910802664236

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Novel Domino Reactions
of (Z,Z)-2,2′-Thiobis(1,3-
diarylprop-2-en-1-ones)
with Acetylacetone and
Ethyl Acetoacetate:
Stereoselective Synthesis
of Highly Functionalized
Dihydrofurans
Beer Mohamed Vinosha a , Subbiah Renuga a
,
Michael Gnanadeebam a , Subbu Perumal b
Antonin Lycka c
&
a Department of Chemistry, Fatima College,
Madurai, India
b School of Chemistry, Madurai Kamaraj University,
Madurai, India
c Research Institute for Organic Synthesis,
Pardubice-Rybitvi, Czech Republic
Version of record first published: 26 Jun 2009.
To cite this article: Beer Mohamed Vinosha , Subbiah Renuga , Michael
Gnanadeebam , Subbu Perumal & Antonin Lycka (2009): Novel Domino Reactions
of (Z,Z)-2,2′-Thiobis(1,3-diarylprop-2-en-1-ones) with Acetylacetone and Ethyl
Acetoacetate: Stereoselective Synthesis of Highly Functionalized Dihydrofurans,
Synthetic Communications: An International Journal for Rapid Communication of
Synthetic Organic Chemistry, 39:15, 2776-2788

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Synthetic Communications1, 39: 2776–2788, 2009
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397910802664236
Novel Domino Reactions of
(Z,Z)-2,20-Thiobis(1,3-diarylprop-2-en-1-ones)
with Acetylacetone and Ethyl Acetoacetate:
Stereoselective Synthesis of Highly
Functionalized Dihydrofurans
Beer Mohamed Vinosha,1 Subbiah Renuga,1 Michael Gnanadeebam,1
Subbu Perumal,2 and Antonin Lycka3
1Department of Chemistry, Fatima College, Madurai, India
2School of Chemistry, Madurai Kamaraj University, Madurai, India
3Research Institute for Organic Synthesis, Pardubice-Rybitvi,
Czech Republic
Abstract: The domino reactions of (Z,Z)-2,20-thiobis(1,3-diarylprop-2-en-1-ones)
with acetylacetone and ethyl acetoacetate in the presence of sodium ethoxide
afforded the corresponding 4,5-dihydrofurans stereoselectively in moderate yields
presumably via a Michael addition–enolization–displacement sequence.
Keywords: Dihydrofurans, domino reactions, stereoselective synthesis, 2,20-thio-bis
(1,3-diarylprop-2-en-1-ones)
INTRODUCTION
Recent investigations from our laboratory have shown that
2,20-thiobis(1,3-diarylprop-2-en-1-ones) 1 and their sulfonyl counterparts
are useful synthons for the construction of heterocycles such as thiazi-
nes,[1a] thianes,[1b] dithianes,[1c] and oxiranes.[2] Reaction of sulfonylbis
compounds with acetylacetone=ethyl acetoacetate afforded mainly
Received September 17, 2008.
Address correspondence to Subbiah Renuga, Department of Chemistry,
Fatima College, Madurai 625018, India. E-mail: s.renuga@gmail.com
2776

Stereoselective Synthesis of Dihydrofurans
2777
thianes.[3] In view of the biological importance of thianes,[4] we planned
to synthesize several novel thianes from 1 in continuation of our research
program to synthesize novel heterocycles employing domino reactions.[5]
However, surprisingly, the reaction of (Z,Z)-2,20-thiobis(1,3-
diarylprop-2-en-1-ones) 1 with acetylacetone=ethyl acetoacetate in the
presence of sodium ethoxide furnished highly substituted dihydrofurans,
and the results are described in this article. It is pertinent to note that
dihydrofurans and furans constitute structural motifs in a wide range
of naturally occurring substances such as alkaloids,[6] lignans,[7] and
pheromones[8] and possess a multitude of biological activities,[9] viz.
anticancer,[10] anti-inflammatory,[11] analgesic,[12] antifungal,[13] and
antirheumatic[14] activites. They also find application as agrochemicals,
as pharmaceuticals, and in the food industry,[15] besides being potential
intermediates in organic synthesis.[16] Hence, there has been a sustained
interest in developing new and efficient methods for the synthesis of
dihydrofurans.[17a–17d]
RESULTS AND DISCUSSION
In the present study, the reaction of (Z,Z)-2,20-thiobis(1,3-diarylprop-2-
en-1-ones) 1 with acetylacetone and ethyl acetoacetate in the presence
of sodium ethoxide afforded mainly dihydrofurans 2 (Scheme 1). In a
typical reaction, a solution of (Z,Z)-2,20-thiobis(1,3-diarylprop-2-en-
1-one) 1, acetylacetone=ethyl acetoacetate, and sodium ethoxide in a
molar ratio of 1:2:2 in dry dimethylformamide (DMF)–ethanol (EtOH)
furnished, after chromatographic separation, moderate to good yields
(58–85%) of 2. Except in one case, where the reaction of 1a with ethyl
acetoacetate (entry 8, Table 1) afforded a mixture of thiane 4
(Ar¼Ar0¼Ph; Z¼COOEt) and dihydrofuran, all other reactions failed
to furnish any characterizable product other than 2. This reaction,
when performed with equimolar amounts of 1, acetylacetone=ethyl
Scheme 1. Synthesis of dihydrofurans.

2778

Stereoselective Synthesis of Dihydrofurans
2779
acetoacetate, and sodium ethoxide, gave diminished yields of 2 along
with unreacted 1 and a small amount of chalcone 3 (5–10%)
(Scheme 1). The yields of dihydrofurans obtained under these conditions
are given in Table 1.
The methods available in the literature for the synthesis of some of
the dihydrofurans reported in this article, namely 2a, 2b, 2g, and 2h, suf-
fer from either the use of hazardous arsonium compounds,[17b] formation
of a mixture of stereoisomers,[17c,17d] or prolonged reaction time.[17a,][17b]
The dihydrofurans 2 were characterized using elemental analyses,
1
infrared (IR), and H, 13C, and two-dimensional NMR spectroscopic
data. The proton signals were assigned on the basis of straightforward
considerations such as intensity, multiplicity, substituent-induced
chemical shifts (SCS values), and H,H-correlation spectroscopy (COSY)
and nuclear overhauser effect spectroscopy (NOESY) spectra. The
carbon signal assignments were based on the carbon chemical shifts in
conjunction with C,H-COSY correlations for proton-bearing carbons
and heteronuclear multiple bond correlations (HMBC) for quaternary
carbons. The signals at 193.7 and 192.0 ppm were assigned respectively
to the acetyl and benzoyl carbonyls on the basis of HMBC. The J value
of 4.8 Hz of the doublets at 5.51 and 4.56 ppm due to H-5 and H-6 respec-
tively reveals their trans relationship. Compounds 2 h–m obtained from
the reaction of 1 with ethyl acetoacetate showed similar spectroscopic
features except for the fact that the signals due to the acetyl group were
replaced by those of the ethoxycarbonyl group. The structures of 2
deduced from NMR spectroscopic data are in good accord with that
determined from the X-ray crystallographic studies on a single crystal
of 2a (Fig. 1).[18] Compound 4 (Ar¼Ar0¼Ph) was characterized by
elemental analysis and NMR spectroscopic data.
The formation of dihydrofurans (Scheme 2) is presumably triggered
by an initial Michael addition of the enolate 5 of acetylacetone=ethyl acet-
oacetate to 1 to give 6, which undergoes ring closure to the dihydrofurans
via displacement of the sulfide function as depicted in 7. The by-product
viz. chalcone 3 in the reaction of 1 with acetylacetone=ethyl acetoacetate
in the presence of 1 mol of base probably arises from the fragmentation of
8 to 9 (Scheme 2). The improved yield of dihydrofuran with 2 mol of base
also supports the mechanism (Table 1). This mechanistic pathway is also
in accordance with that reported in the literature for the formation of
dihydrofurans.[17a–17c]
The predominant formation of dihydrofurans in the reaction of 1
with acetylacetone=ethyl acetoacetate in contrast to the formation of
thianes by double Michael addition in the reaction of the sulfone counter-
part of 1[3] deserves mention. Probably in the case of sulfone, after the
first Michael addition of acetylacetone=ethyl acetoacetate, the second

2780
B. M. Vinosha et al.
Figure 1. X-ray structure of dihydrofuran 2a.
Scheme 2. Mechanism of formation of dihydrofurans 2 and chalcones 3 from 1.

Stereoselective Synthesis of Dihydrofurans
2781
Michael addition leading to thianes is presumably favored over the
displacement reaction leading to dihydrofurans because there are two
powerful electron-withdrawing groups favoring the former reaction over
the latter.
CONCLUSIONS
In conclusion, the present work describes the predominant formation of
highly functionalized dihydrofurans via domino reactions of acetylaceto-
ne=ethyl acetoacetate with (Z,Z)-2,20-thiobis(1,3-diarylprop-2-en-1-ones)
in DMF in the presence of sodium ethoxide, in contrast to thianes
obtained from the reaction of the corresponding sulfones observed in
an earlier study. Investigations on the utility of the dihydrofurans as
synthons in the construction of novel heterocycles currently are being
explored in our group.
EXPERIMENTAL
The melting points are uncorrected. Infrared (IR) spectra were recorded
on a Perkin-Elmer IR-577 instrument with KBr. NMR spectra were
recorded at 25ꢀC on either a Bruker AMX 300 instrument operating at
300 MHz for 1H and at 75 MHz for 13C or a Bruker AMX 360 instrument
operating at 360 MHz for 1H and at 90 MHz for 13C. Solutions in CDCl3
were approximately 0.05 M, and chemical shifts were referenced intern-
ally to TMS in d scale (ppm). Two-dimensional NMR measurements,
H,H-COSY, C,H-COSY, NOESY, and HMBC, have also been
performed using these instruments. Standard Bruker software was used
throughout. Elemental analyses were performed on a Perkin-Elmer
2400 series II Elemental CHNS Analyser. The Michael acceptor 1 was
obtained by a literature method.[19]
General Procedure for the Synthesis of 4,5-Dihydrofurans 2
A solution of acetylacetone (1.0 g, 10 mmol) in absolute ethanol
(20 mL) was added dropwise with stirring to a solution of sodium
ethoxide prepared by dissolving sodium metal (0.24 g, 10 mmol) in
absolute ethanol (8 mL). To this mixture, a solution of 2,20-thio-
bis(1,3-diphenylprop-2-en-1-one) (2.2 g, 5 mmol) in dry dimethylforma-
mide (50 mL) was added dropwise with stirring. After the addition
was complete, the reaction mixture was kept at room temperature

2782
B. M. Vinosha et al.
for 1 h and then poured into ice water. The separated solid after
chromatographic separation using ethyl acetate–petroleum ether [3:97
(v=v)] gave 2a as a colorless solid. A similar procedure was followed
for the reaction of 2,20-thiobis(1,3-diphenylprop-2-en-1-one) with ethyl
acetoacetate.
Data
trans-1-(5-Benzoyl-2-methyl-4-phenyl-4,5-dihydro-3-furanyl)-1-
ethanone (2a)
Obtained as a colorless solid (2.2 g, 73%). Mp 140–142ꢀC; lit. mps are
1
139–140[17a], 114.5–115.8[17b] and 125–127.[17c,17d] The IR and H and
13C NMR spectroscopic features of 2a agree with those reported in the
literature.[17a]
trans-1-[5-Benzoyl-4-(4-chlorophenyl)-2-methyl-4,5-dihydro-3-
furanyl]-1-ethanone (2b)
Obtained as a semisolid.[17b–17d] 1H NMR (300 MHz, CDCl3) d: 1.97
(s, 3H, COMe), 2.45 (s, 3H, ¼CMe), 4.52 (d, 1H, J ¼ 4.8 Hz, H-4),
5.62 (d, 1H, J ¼ 4.8 Hz, H-5), 7.19 (d, 2H, J ¼ 8.4 Hz), 7.33 (d, 2H,
J ¼ 8.4 Hz), 7.46 (t, 2H, J ¼ 7.5 Hz), 7.61 (t, 1H, J ¼ 7.5 Hz), 7.85 (d,
2H, J ¼ 7.5 Hz); 13C NMR (75 MHz, CDCl3) d: 14.9 (¼ CMe), 29.4
(COMe), 51.1 (C-4), 88.9 (C-5), 115.8 (C-3), 128.7, 128.8, 128.9,
129.1, 133.1, 133.3, 134.0, 140.6 (aromatic carbons), 168.3 (C-2),
192.9 (PhCO), 193.6 (COMe). Anal. calcd. for C20H17ClO3: C, 70.49;
H, 5.03. Found: C, 70.59; H, 5.00.
trans-1-[5-(4-Chlorobenzoyl)-2-methyl-4-phenyl-4,5-dihydro-3-
furanyl]-1-ethanone (2c)
Obtained as a colorless solid. Mp 116–118ꢀC; 1H NMR (300 MHz,
CDCl3) d: 1.94 (s, 3H, COMe), 2.46 (s, 3H, ¼CMe), 4.56 (d, 1H,
J ¼ 4.8 Hz, H-4), 5.59 (d, 1H, J ¼ 4.8 Hz, H-5), 7.24–7.47 (m, 7H), 7.82
(d, 2H, J ¼ 8.7 Hz); 13C NMR (75 MHz, CDCl3) d: 14.9 (¼CMe), 29.6
(COMe), 51.7 (C-4), 89.3 (C-5), 115.8 (C-3), 127.5, 127.8, 129.1 (6),
129.1 (8), 130.5, 131.8, 140.6, 142.0 (aromatic carbons), 168.1 (C-2),
192.2 (PhCO), 194.2 (COMe). Anal. calcd. for C20H17ClO3: C, 70.49;
H, 5.03. Found: C, 70.37; H, 5.04.

Stereoselective Synthesis of Dihydrofurans
2783
trans-1-[5-(4-Chlorobenzoyl)-4-(4-fluorophenyl)-2-methyl-4,5-
dihydro-3-furanyl]-1-ethanone (2d)
Obtained as a colorless solid. Mp 136–138ꢀC; IR (KBr) n 2916, 1689, 1593,
1230cmꢁ1; 1H NMR (300MHz, CDCl3) d: 1.98 (s, 3H, COMe), 2.45 (s, 3H,
¼CMe), 4.57 (d, 1H, J ¼ 4.8 Hz, H-4), 5.54 (d, 1H, J ¼ 4.8 Hz, H-5),
7.04–7.27 (m, 4H, aryl), 7.46 (d, 2H, J ¼ 8.4 Hz), 7.82 (d, 2H, J ¼ 8.4 Hz);
13C NMR (75 MHz, CDCl3) d: 15.0 (¼CMe), 29.6 (COMe), 50.9 (C-4),
89.3 (C-5), 116.0 (C-3), 129.1, 129.2 (0), 129.2 (4), 130.5, 131.6, 138.0,
141.0 (aromatic carbons), 168.0 (C-2), 192.2 (PhCO), 193.9 (COMe). Anal.
calcd. for C20H16ClFO3: C, 66.95; H, 4.49. Found: C, 66.74; H, 4.47.
trans-1-[5-(4-Chlorobenzoyl)-4-(4-chlorophenyl)-2-methyl-
4,5-dihydro-3-furanyl]-1-ethanone (2e)
Obtained as a colorless solid. Mp 144–146ꢀC; 1H NMR (360 MHz,
CDCl3) d: 1.97 (s, 3H, -COMe), 2.43 (s, 3H, ¼CMe), 4.56 (d, 1H,
J ¼ 4.8 Hz, H-4), 5.51 (d, 1H, J ¼ 4.8 Hz, H-5), 7.18 (d, 2H, J ¼ 8.3 Hz),
7.33 (d, 2H, J ¼ 8.3 Hz), 7.45 (d, 2H, J ¼ 7.2 Hz), 7.80 (d, 2H, J ¼ 7.2 Hz);
;
13C NMR (90 MHz, CDCl3) d: 14.9 (¼CMe), 29.5 (COMe), 51.0 (C-4),
89.1 (C-5), 115.9 (C-3), 128.9, 129.2, 129.3, 130.5, 131.8, 133.6, 140.6,
140.8 (aromatic carbons), 168.0 (C-2), 192.0 (PhCO), 193.7 (COMe).
Anal. calcd. for C20H16Cl2O3: C, 64.02; H, 4.30. Found: C, 64.10; H, 4.28.
trans-1-[5-(4-Chlorobenzoyl)-2-methyl-4-(4-methylphenyl)-
4,5-dihydro-3-furanyl]-1-ethanone (2f)
Obtained as a colorless solid. Mp 116–118ꢀC; IR (KBr) n 2910, 1688,
1
1590, 1232 cmꢁ1; H NMR (300 MHz, CDCl3) d: 1.93 (s, 3H, COMe),
2.36 (s, 3H, p-tolyl-Me), 2.45 (s, 3H, ¼CMe), 4.49 (d, 1H, J ¼ 4.8 Hz,
H-4), 5.57 (d, 1H, J ¼ 4.8 Hz, H-5), 7.12–7.20 (m, 4H), 7.45 (d, 2H,
J ¼ 8.1 Hz), 7.81 (d, 2H, J ¼ 8.1 Hz); 13C NMR (75 MHz, CDCl3) d:
14.7 (¼CMe), 20.9 (p-tolyl-Me), 29.4 (COMe), 51.3 (C-4), 89.3 (C-5),
115.5 (C-3), 127.2, 128.9, 129.6, 130.3, 131.5, 137.3, 138.8, 140.4
(aromatic carbons), 167.9 (C-2), 192.1 (PhCO), 194.1 (COMe). Anal.
calcd. for C21H19ClO3: C, 71.08; H, 5.40. Found: C, 71.23; H, 5.43.
trans-1-[2-Methyl-5-(4-methylbenzoyl)-4-phenyl-4,5-dihydro-3-
furanyl]-1-ethanone (2g)
Obtained as a colorless solid. Mp 99–100ꢀC[17a]; IR (KBr) n 2920, 1695,
1
1616, 1224 cmꢁ1; H NMR (300 MHz, CDCl3) d: 1.93 (s, 3H, COMe),

2784
B. M. Vinosha et al.
2.43 (s, 3H), 2.47 (s, 3H), 4.51 (d, 1H, J ¼ 4.5 Hz, H-4), 5.64 (d, 1H,
J ¼ 4.5 Hz, H-5), 7.24–7.40 (m, 7H, aryl), 7.77 (d, 2H, J ¼ 8.1 Hz); 13C
NMR (75 MHz, CDCl3) d: 15.0 (¼CMe), 21.8 (p-tolyl-Me), 29.6
(COMe), 52.0 (C-4), 89.4 (C-5), 115.8 (C-3), 127.6, 127.7, 129.1, 129.2,
129.5, 131.8, 142.2, 145.2 (aromatic carbons), 168.5 (C-2), 192.9 (PhCO),
194.3 (COMe). Anal. calcd. for C21H20O3: C, 78.73; H, 6.29. Found: C,
78.84; H, 6.27.
trans-5-Benzoyl-2-methyl-4-phenyl-4,5-dihydrofuran-3-carboxylic
acid ethyl ester (2 h) and 4-Acetyl-2,6-dibenzoyl-4-
ethoxycarbonyl-3,5-diphenylthiane (4)
The mixture of products 2h and 4 was separated by column chromatogra-
phy using ethyl acetate–petroleum ether [2:98 (v=v)]. Compound 2h was
obtained as a colorless liquid (1.9 g, 58%). The IR and 1H and
13C NMR spectroscopic features of 2h agree with those reported in the
literature.[17c,17d]
1
Compound 4 was obtained as a colorless solid. Mp 194–196ꢀC; H
NMR (300 MHz, CDCl3) d: 1.04 (t, 3H, J ¼ 7.2 Hz, OCH2CH3), 1.34 (s,
3H, COCH3), 4.14 (q, 2H, J ¼ 7.2 Hz, OCH2CH3), 4.44 (d, 2H,
J ¼ 11.4 Hz, H-3,5), 6.28 (d, 2H, J ¼ 11.4 Hz, H-2,6), 7.04–7.14 (m,
10H), 7.41 (m, 4H), 7.52 (t, 2H, J ¼ 7.5 Hz), 7.91 (d, 4H, J ¼ 7.9 Hz);
13C NMR (75 MHz, CDCl3) d: 13.4 (OCH2CH3), 33.9 (COMe), 45.8
(C-3,5), 51.9 (C-2,6), 61.2 (OCH2CH3), 69.8 (C-4), 127.5, 128.3, 128.4,
128.6, 129.1 133.4, 136.1, 138.5 (aromatic carbons), 171.8, 194.9,
206.3. Anal. calcd. for C36H32O5S: C, 74.98; H, 5.59. Found: C,
74.81; H, 5.61.
trans-5-Benzoyl-4-(4-chlorophenyl)-2-methyl-4,5-dihydrofuran-
3-carboxylic Acid Ethyl Ester (2i)
1
Obtained as a semisolid. H NMR (300 MHz, CDCl3) d: 1.01 (t, 3H,
J ¼ 7.2 Hz, COOCH2Me), 2.41 (d, 3H, J ¼ 1.2 Hz, ¼CMe), 3.98 (m,
2H, COOCH2Me), 4.37 (dd, 1H, J ¼ 1.2 & 4.8 Hz, H-4), 5.67 (d, 1H,
J ¼ 4.8 Hz, H-5), 7.16 (d, 2H, J ¼ 8.4 Hz), 7.30 (d, 2H, J ¼ 8.4 Hz), 7.42
(t, 2H, J ¼ 7.5 Hz), 7.55 (t, 1H, J ¼ 7.5 Hz), 7.81 (d, 2H, J ¼ 7.2 Hz);
13C NMR (75 MHz, CDCl3) d: 13.9 (COOCH2CH3), 14.0 (¼CMe),
50.9 (C-4), 59.5 (COOCH2CH3), 88.8 (C-5), 106.4 (C-3), 128.6 (6),
128.7 (1), 128.8, 129.1, 133.1, 133.3, 133.9, 140.9 (aromatic carbons),
164.5 (COOCH2CH3), 168.4 (C-2), 193.0 (PhCO). Anal. calcd. for
C21H19ClO4: C, 68.02; H, 5.16; Found: C, 68.12; H, 5.13.

Stereoselective Synthesis of Dihydrofurans
2785
trans-5-(4-Chlorobenzoyl)-2-methyl-4-phenyl-4,5-dihydrofuran-
3-carboxylic Acid Ethyl Ester (2j)
1
Obtained as a semisolid; H NMR (300 MHz, CDCl3) d: 1.03 (t, 3H,
J ¼ 6.6 Hz, COOCH2Me), 2.42 (s, 3H, ¼CMe), 3.94 (m, 2H,
COOCH2Me), 4.37 (distorted dd, 1H, H-4), 5.66 (d, 1H, J ¼ 4.8 Hz,
H-5), 7.09–7.55 (m, 7H), 7.78 (d, 2H, J ¼ 7.8 Hz); 13C NMR (75 MHz,
CDCl3) d: 13.9 (COOCH2CH3), 14.0 (¼CMe), 51.5 (C-4), 59.5
(COOCH2CH3), 89.1 (C-5), 106.8 (C-3), 127.4, 127.8, 129.0, 129.4,
130.5, 131.6, 140.4, 142.2 (aromatic carbons), 164.7 (COOCH2CH3),
168.1 (C-2), 192.3 (PhCO). Anal. calcd. for C21H19ClO4: C, 68.02; H,
5.16. Found: C, 67.94; H, 5.19.
trans-5-(4-Chlorobenzoyl)-4-(4-fluorophenyl)-2-methyl-4,
5-dihydrofuran-3-carboxylic Acid Ethyl Ester (2k)
Obtained as a colorless solid. Mp 118–120ꢀC; IR (KBr) n 2983, 1693,
1
1654, 1208 cmꢁ1; H NMR (300 MHz, CDCl3) d: 1.06 (t, 3H, J ¼ 7.2 Hz,
COOCH2Me), 2.41 (d, 3H, J ¼ 1.2 Hz, ¼CMe), 3.91–4.04 (m, 2H,
COOCH2Me), 4.43 (dd, 1H, J ¼ 1.2 & 4.8 Hz, H-4), 5.61 (d, 1H,
J ¼ 4.8 Hz, H-5), 7.00–7.06 (m, 2H), 7.20–7.24 (m, 2H), 7.43 (d, 2H,
J ¼ 6.9 Hz), 7.80 (d, 2H, J ¼ 6.9 Hz); 13C NMR (75 MHz, CDCl3) d:
13.9 (COOCH2CH3), 14.0 (¼CMe), 50.7 (C-4), 59.6 (COOCH2CH3),
89.0 (C-5), 106.8 (C-3), 115.5, 115.8, 128.9 (6), 129.0 (7), 129.1 (3),
130.3, 131.7, 138.0 (7), 138.1 (2), 140.5 (aromatic carbons), 164.6
(COOCH2CH3), 168.1 (C-2), 192.2 (ArCO). Anal. calcd. for
C21H18ClFO4: C, 64.87; H, 4.67. Found: C, 64.99; H, 4.65.
trans-5-(4-Chlorobenzoyl)-4-(4-chlorophenyl)-2-methyl-4,
5-dihydrofuran-3-carboxylic Acid Ethyl Ester (2l)
Obtained as a colorless solid. Mp 134–136ꢀC; IR (KBr) n 2981, 1693,
1
1654, 1205 cmꢁ1; H NMR (300 MHz, CDCl3) d: 1.06 (t, 3H, J ¼ 7.2 Hz,
Hz, COOCH2Me), 2.41 (s, 3H, ¼CMe), 3.98 (m, 2H, COOCH2Me), 4.43
(d, 1H, J ¼ 4.2 Hz, H-4), 5.60 (d, 1H, J ¼ 4.8 Hz, H-5), 7.19 (d, 2H,
J ¼ 8.1 Hz) 7.32 (d, 2H, J ¼ 8.1 Hz) 7.43 (d, 2H, J ¼ 8.4 Hz) 7.78 (d, 2H,
J ¼ 8.4 Hz); 13C NMR (75 MHz, CDCl3) d: 13.9 (COOCH2CH3), 14.0
(¼CMe), 50.8 (C-4), 59.6 (COOCH2CH3), 88.8 (C-5), 106.6 (C-3),
128.8, 128.9, 129.1, 130.3, 131.6, 133.1, 140.5, 140.8 (aromatic carbons),
164.5 (COOCH2CH3), 168.2 (C-2), 192.0 (ArCO). Anal. calcd. for
C21H18Cl2O4: C, 62.24; H, 4.48. Found: C, 62.31; H, 4.45.

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B. M. Vinosha et al.
trans-5-(4-Chlorobenzoyl)-2-methyl-4-(4-methylphenyl)-4,
5-dihydrofuran-3-carboxylic Acid Ethyl Ester (2m)
Obtained as a colorless solid. Mp 106–108ꢀC; IR (KBr) n 2979, 1693,
1
1653, 1206 cmꢁ1; H NMR (300 MHz, CDCl3) d: 1.07 (t, 3H, J ¼ 7.2 Hz,
COOCH2Me), 2.36 (s, 3H, p-tolyl-Me), 2.43 (s, 3H, ¼CMe), 3.97 (m, 2H,
-COOCH2CH3), 4.36 (dd, 1H, J ¼ 1.2 & 4.8 Hz, H-4), 5.65 (d, 1H,
J ¼ 4.8 Hz, H-5), 7.12–7.27 (m, 4H), 7.43 (d, 2H, J ¼ 8.7 Hz), 7.79 (d,
2H, J ¼ 8.7 Hz); 13C NMR (75 MHz, CDCl3) d: 14.0 (-COOCH2CH3),
14.0(5) (¼CMe), 21.1 (p-tolyl-Me), 51.3 (C-4), 59.6 (-COOCH2CH3),
89.2 (C-5), 107.0 (C-3), 127.3, 129.1, 129.4, 130.3, 131.7, 137.0, 139.3,
140.4 (aromatic carbons), 164.8 (COOCH2CH3), 168.0 (C-2), 192.4
(ArCO). Anal. calcd. for C22H21ClO4: C, 68.66; H, 5.50. Found: C,
68.54; H, 5.51.
ACKNOWLEDGMENTS
S. R. and M. G. thank the University Grants Commission for the finan-
cial support under Major Research Project F. 31-96=2005 (SR). S. R. and
M. G. also thank the secretary and the principal, Fatima College,
Madurai, for providing facilities.
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