Microwave assisted urea-acetic acid catalyzed knoevenagel condensation of ethyl cyanoacetate and 1,3-Thiazolidine-2,4-dione with aromatic aldehydes under solvent free condition

Article abstract of DOI:10.14233/ajchem.2017.20695

Knoevengel condensation reaction of various aromatic aldehydes with ethyl cyanoacetate and 1,3-thiazolidinone-2,4-diones catalyzed by urea-acetic acid under solvent free condition where olefinic products were obtained in high yield within short reaction time.

Full text of DOI:10.14233/ajchem.2017.20695

Asian Journal of Chemistry; Vol. 29, No. 11 (2017), 2401-2405
ASIAN JOURNAL OF CHEMISTRY
https://doi.org/10.14233/ajchem.2017.20695
Microwave Assisted Urea-Acetic Acid Catalyzed Knoevenagel Condensation of Ethyl Cyanoacetate
and 1,3-Thiazolidine-2,4-dione with Aromatic Aldehydes under Solvent Free Condition
PRAVIN. T. TRYAMBAKE
Department of Chemistry, S.N. Arts, D.J.M. Commerce and B.N.S. Science College, Sangamner-422 605, India
Corresponding author: Fax: +91 2425 225893; E-mail: pravintryambake21@rediffmail.com
Received: 8 April 2017;
Accepted: 5 June 2017;
Published online: 29 September 2017;
AJC-18559
Knoevengel condensation reaction of various aromatic aldehydes with ethyl cyanoacetate and 1,3-thiazolidinone-2,4-diones catalyzed by
urea-acetic acid under solvent free condition where olefinic products were obtained in high yield within short reaction time.
Keywords: Knoevengel condensation, Solvent free, Urea-Acetic acid.
[27] and ethylenediamine diacetate [28]. Recently, ionic liquids
catalyzed synthesis of 5-arylidene-2,4-thiazolidinediones have
also been reported [29,30]. All the above methods have their
own advantages but also suffer from one or more disadvantages
such as long reaction time, low to moderate yields, tedious
work-up procedures, requirement of special apparatus and use
of organic solvents.
INTRODUCTION
Knoevenagel condensation is an important reaction in
organic chemistry by which carbon-carbon double bond is
formed. One of the product ethyl α-cyanocinnamates is used
as an important intermediate for the synthesis of different
pharmaceutically important organic compounds and also has
application in making paper, dyes, fibers, plastics etc. [1]. Other
product 5-arylidene derivatives of 4-thiazolidinones are well
known in the pharmaceutical industry and have been shown a
broad spectrum of biological activities including anti-
inflammatory [2a], antibacterial [2b], antiviral [2c], antimicrobial
[2d], antifungal [2e] and possess aldose reductase inhibitors
[2f], antidiabetic activity [2g-k].
In present work, urea-acetic acid couple is used as a catalyst
for Knoevengel condensation between aromatic aldehydes and
compounds with active methylene group like ethyl cyano-
acetate (Scheme-I) and 1,3-thiazolidinone-2,4-dione (Scheme-
II) under microwave irradiation. Both are non-toxic, easily
available, easy to handle and low cost compounds.
A number of synthetic strategies have been developed for
the Knoevengel condensation of aromatic aldehydes and ethyl
cyanoacetate. This reaction is catalyzed by organic bases or
with variety of catalyst like zeolites [3], AlPO4-Al2O3 [4],
LaCl3·H2O [5], I2/K2CO3 [6], CTMAB [7], TEBA [8], NH4OAc-
Basic alumina [9], H3PW12O40 [10], NaF and LiCl [11], MgBr2·
OEt2 [12], TiCl4/Base [13], MgO and ZnO [14], ZnCl2 [15],
lipase as a biocatalyst [16], etc. The synthesis of 5-arylidene-
2,4-thiazolidinediones such as sodium acetate in acetic acid
under reflux conditions [17], microwave irradiation [18],
piperidine in ethanol [19a], piperidinium acetate in toluene
under reflux conditions [19b], piperidinium acetate in DMF
under microwave irradiation [20], glycine and sodium carbonate
in H2O under reflux conditions [21], grinding with ammonium
acetate in the absence of solvents [22], alum in H2O [23], Baker’s
yeast [24], KF-Al2O3 under microwave irradiation [25], glycine
under microwave irradiation [26], polyethylene glycol-300
EXPERIMENTAL
Melting points were determined in open capillary tubes
and are uncorrected. IR spectra were recorded with a Shimadzu
1
IR-408 spectrometer. H NMR spectra were determined in
CDCl3/DMSO-d6 solution on a Bruker Avance II (400 MHz)
NMR spectrometer and TMS was used as a internal standard.
Mass spectra wererecorded on aWATERS, Q-TOFMICROMASS
(LC-MS). Domestic microwave oven (Samsung) was used at
Power 600 W.
General procedure for synthesis of ethyl α-cyanocinna-
mates (3a-n) and 5-arylidine-2,4-thiazolidinediones (5a-l):
A mixture of aromatic aldehydes (4.7 mmol), ethyl cyano-
acetate (0.531 g, 4.7 mmol) or 1,3-thiazolidinone-2,4-dione
(0.550 g, 4.7 mmol) and urea-acetic acid in (0.028 g : 0.028 g,
10 mmol % 1:1) was taken in an Erlenmeyer flask and subjected
to microwave irradiation at 600 W at 10 s interval for a specified

2402 Tryambake
Asian J. Chem.
time as indicated in Tables 1 and 2. The completion of the
reaction was monitored byTLC (20 % ethyl acetate in n-hexane).
The reaction mixture was cooled to room temperature and
treated with cold water the product thus obtained was filtered,
dried and recrystallized from ethanol affording pure products.
2231, 1725, 1603, 1527, 1343; 1H NMR (400 MHz, CDCl3):
δ = 8.7 (s, 1H, CH), 8.3 (s, 1H, phenyl), 7.8 (m, 2 H, phenyl),
7.7 (t, 1H, phenyl), 4.4 (q, J = 7.12 Hz, 2H, CH2), 1.4 (t, J =
7.1 Hz, 3H, CH3). LC-MS: m/z (M +1) calcd. for C12H10N2O4:
247; found: 247.1
Ethyl (E)-2-cyano-3-(4-methoxyphenyl)-2-propenoate
(3j): Yield: 90 %; m.p.: 80-82 °C (lit. 86 °C [16]); FTIR (KBr,
Physical and spectral data
1
νmax, cm–1): 2990, 2941, 2841, 2213, 1716, 1585; H NMR
Ethyl (E)-2-cyano-3-phenyl-2-propenoate (3a): Yield:
96 %; m.p.: 50-51 °C (lit. 50 °C [11]); FTIR (KBr, νmax, cm–1):
2982, 2222, 1725, 1605; 1H NMR (400 MHz, CDCl3): δ = 8.2
(s, 1H, CH), 7.9 (m, 2H, phenyl), 7.5 (m, 3H phenyl), 4.3–4.4
(q, J = 7.12 Hz, 2H, CH2), 1.3–1.4 (t, J = 7.12 Hz, 3H, CH3);
LC-MS: m/z (M +1) calcd. for C12H11NO2 : 202; found: 202.
Ethyl (E)-2-cyano-3-(3-nitrophenyl)-2-propenoate
(3b): Yield: 96 %; m.p.: 130-132 °C (lit. 130 °C [11]); FTIR
(400 MHz, CDCl3): δ = 8.1 (s, 1H, CH), 8.0 (d, 2H, phenyl),
7.0 (d, J = 7.0 Hz, 2H, phenyl), 4.3 (q, J = 7.12 Hz, 2H, CH2),
3.8 (s, 3H, OCH3), 1.3–1.4 (t, J = 7.12 Hz, 3H, CH3).
Ethyl (E)-2-cyano-3-(3,4,5-trimethoxyphenyl)-2-
propenoate (3k): Yield: 90 %; m.p.: 98-99 °C; FTIR (KBr,
1
νmax, cm–1): 2981, 2948, 2844, 2218, 1730, 1601, 1577; H
NMR (400 MHz, CDCl3): δ = 8.1 (s, 1H, CH), 7.3 (s, 2H,
phenyl), 4.4 (q, J = 7.12 Hz, 2H, CH2), 3.96 (s, 3H, CH3),
3.93 (s, 6H, CH3), 1.4 (t, J = 7.12 Hz, 3H, CH3). LC-MS: m/z
(M +1) calcd. for C15H17NO5: 292; found: 292.1.
(KBr, νmax, cm–1): 2987, 2224, 1719, 1605, 1528, 1355; H
1
NMR (400 MHz, DMSO-d6): δ = 8.49 (s, 1H, CH), 8.9 (s, 1H,
phenyl), 8.41 (t, 2H, phenyl), 7.82 (t, 1H, phenyl), 4.4 (q, J =
6.8 Hz, 2H, CH2), 1.4 (t, J = 6.8 Hz, 3H, CH3).
Ethyl (E)-2-cyano-3-(2-methoxyphenyl)-2-propenoate
(3l): Yield: 94 %; m.p.: 70-72 °C (lit. 70 °C [16]); FTIR (KBr,
Ethyl (E)-2-cyano-3-(2-chlorophenyl)-2-propenoate
(3c): Yield: 92 %; m.p.: 62-64 °C; FTIR (KBr, νmax, cm–1): 2994,
2223, 1731, 1609, 758; 1H NMR (400 MHz, CDCl3): δ = 8.69
(s, 1H, CH), 8.2 (d, 1H, phenyl), 7.5 (m, 2H, phenyl), 7.4 (m,
1H, phenyl), 4.4 (q, J = 7.2 Hz, 2H, CH2), 1.4 (t, J = 7.2 Hz,
3H, CH3); LC-MS: m/z (M +1) calcd. for C12H10NO2Cl : 236;
found: 236
1
νmax, cm–1): 2988, 2942, 2835, 2223, 1709, 1596; H NMR
(400 MHz, CDCl3): δ = 8.7 (s, 1H, CH), 8.3 (d, 1H, phenyl),
7.5 (t, 1H, phenyl), 7.0 (t, 1H, phenyl), 6.9 (d, 1H, phenyl),
4.3–4.4 (q, J = 7.12 Hz, 2H, CH2), 3.9 (s, 3H, OCH3), 1.3–1.4
(t, J = 7.12 Hz, 3H, CH3).
Ethyl (E)-2-cyano-3-(4-fluorophenyl)-2-propenoate
(3m): Yield: 94 %; m.p.: 96-98 °C (lit. 97 °C [16]); FTIR
(KBr, νmax, cm–1): 2998, 2224, 1717, 1593, 762; 1H NMR (400
MHz, CDCl3): δ = 8.2 (s, 1H, CH), 8.0 (t, 2H, phenyl), 7.2 (t,
2H, phenyl,), 4.4 (q, J = 7.12 Hz, 2 H, CH2), 1.4 (t, J = 7.12
Hz, 3H, CH3).
Ethyl (E)-2-cyano-3-(3-methoxy 4-hydroxyphenyl)-2-
propenoate (3d):Yield: 95 %; m.p.: 112 °C (lit. 114 °C [16]);
FTIR (KBr, νmax, cm–1): 3376, 2983, 2940, 2218, 1703, 1575;
1H NMR (400 MHz, CDCl3): δ = 8.1 (s, 1H, CH), 7.8 (s, 1H,
phenyl), 7.4 (d, 1H, phenyl), 7.0 (d, 1H, phenyl), 6.5 (s, 1H,
OH), 4.3 (q, J = 6.8 Hz, 2H, CH2), 3.9 (s, 3H, OCH3), 1.4 (t, J
= 6.8 Hz, 3H, CH3).
Ethyl (E)-2-cyano-3-(1-naphthyl)-2-propenoate (3n):
Yield: 90 %; m.p.: 95-96 °C; FTIR (KBr, νmax, cm–1): 2969, 2223,
1718, 1603; 1H NMR (400 MHz, CDCl3): δ = 9.1 (s, 1H, CH),
8.3 (d, 1H,Ar), 8.0 (t, 2H,Ar), 7.9 (d, 1H,Ar), 7.6 (m, 3H,Ar),4.4
(q, J = 7.12 Hz, 2 H, CH2), 1.4 (t, J = 7.12 Hz, 3H, CH3); LC-
MS: m/z (M +1) calcd. for C16H13NO2: 253; found: 253.1
5-(Benzylidene)-1,3-thiazolidine-2,4-dione (5a):Yield:
93 %; m.p.: 240 °C (lit. 240 °C [22]); IR (KBr, νmax, cm–1):
3140, 3031, 2785, 1738, 1688); 1H NMR (400 MHz, DMSO-
d6): δ = 12.5 (s, 1H, NH), 7.7 (s, 1H, =CH), 7.4-7.5 (m, 5H,
Ar); LC-MS: m/z (M +1) calcd. for C10H7NO2S: 206; found: 206
5-[(Furan-2-yl)methylidene]-1,3-thiazolidine-2,4-dione
(5b): Yield: 91 %; m.p.: 233-235 °C (lit. 231-233 °C [28]); IR
Ethyl (E)-2-cyano-3-(3-chlorophenyl)-2-propenoate
(3e): Yield: 98 %; m.p.: 102-103 °C; FTIR (KBr, νmax, cm–1):
2985, 2221, 1714, 1609, 759; 1H NMR (400 MHz, CDCl3): δ
= 8.1 (s, 1H, CH), 7.9 (d, 2H, phenyl), 7.5 (d, 1H, phenyl), 7.4
(t, 1H, phenyl), 4.4 (q, J = 6.8 Hz, 2 H, CH2), 1.4 (t, J = 6.8
Hz, 3H, CH3).
Ethyl (E)-2-cyano-3-furyl-2-propenoate (3f): Yield: 92
%; m.p.: 94-96 °C (lit. 95 °C [11]); FTIR (KBr, νmax, cm–1):
2988, 2222, 1716, 1620; 1H NMR (400 MHz, CDCl3): δ = 8.0
(s, 1H, CH), 7.7 (d, 1H, furyl), 7.4 (d, 1H, furyl), 6.6 (t, 1H,
furyl), 4.3 (q, J = 7.12 Hz, 2 H,CH2), 1.4 (t, J = 7.12 Hz, 3H,CH3).
Ethyl (E)-2-cyano-3-(4-chlorophenyl)-2-propenoate
(3g): Yield: 94 %; m.p.: 90-92 °C (lit. 92-93 °C [11]); FTIR
(KBr, νmax, cm–1): 2988, 2221, 1722, 1608, 758; 1H NMR (400
MHz, CDCl3): δ = 8.2 (s, 1H, CH), 7.9 (d, 2H, phenyl), 7.4 (d,
2H, phenyl), 4.4 (q, J = 7.12 Hz, 2H, CH2), 1.4 (t, J = 7.12
Hz, 3H, CH3).
1
(KBr, νmax, cm–1): 3131, 3031, 2800, 1785, 1685; H NMR
(400 MHz, DMSO-d6): δ = 12.3 (s, 1H, NH), 7.5 (s, 1H, =CH),
7.9 (d, 1H, Ar), 6.9 (d, 1H, Ar), 6.6 (m, 1H, Ar).
5-(3,4,5-Trimethoxybenzylidene)-1,3-thiazolidine-2,4-
dione (5c): Yield: 90 %; m.p.: 210 °C; IR (KBr, νmax, cm–1):
3197, 2993, 2949, 1749, 1699; 1H NMR (400 MHz, DMSO-
d6): δ = 12.55 (s, 1H, NH), 7.71 (s, 1H, =CH), 6.8 (s, 2H, Ar),
3.7 (s, 3H, CH3). 3.8 (s, 6H, 2CH3); LC-MS: m/z (M +1) calcd.
for C13H13NO5S: 296.1; found: 296.1.
Ethyl (E)-2-cyano-3-(4-hydroxyphenyl)-2-propenoate
(3h): Yield: 90 %; m.p.: 170-172 °C (lit. 168 °C [16]); FTIR
(KBr, νmax, cm–1): 3253, 2988, 2231, 1731, 1713; H NMR
1
(400 MHz, DMSO-d6): δ = 10.5 (s, 1H, OH), 8.1 (s, 1H, CH),
7.9 (d, 2H, phenyl), 6.9 (d, 2H, phenyl), 4.3 (q, J = 7.12 Hz,
2H, CH2), 1.38 (t, J = 7.12 Hz, 3H,CH3) ppm.
5-[(Naphthalene-1-yl) methylidene]-1,3-thiazolidine-
2,4-dione (5d): Yield: 87 %; m.p.: 234-236 °C; IR (KBr, νmax
,
1
cm–1): 3120, 3010, 2766, 1742, 1693; H NMR (400 MHz,
DMSO-d6): δ = 12.64 (s, 1H, NH), 8.41 (s, 1H, =CH), 8.1 (d,
1H, Ar), 7.9 (m, 2H, Ar), 7.5-7.6 (m, 4H, Ar).
Ethyl (E)-2-cyano-3-(2-nitrophenyl)-2-propenoate (3i):
Yield: 95 %; m.p.: 118-120 °C; FTIR (KBr, νmax, cm–1): 2995,

Vol. 29, No. 11 (2017)
Microwave Assisted Knoevenagel Condensation of Ethyl Cyanoacetate and 1,3-Thiazolidine-2,4-dione 2403
O
H
R
COOEt
COOEt
5-(4-Hydroxybenzylidene)-1,3-thiazolidine-2,4-dione
(5e):Yield: 86 %; m.p.: 310 °C (lit. 309-310 °C [28]); IR (KBr,
Urea-Acetic acid, 1:1,10 mol%
Microwave
+
R
H
CN
CN
1
νmax, cm–1): 4302, 3126, 3004, 2790, 1724, 1678; H NMR
1a-k
3a-k
2
Scheme-I: Synthesis of ethyl α-cyanocinnamates
(400 MHz, DMSO-d6): δ = 12.35 (s, 1H, NH), 10.21 (s, 1H,
OH), 7.6 (s, 1H, =CH), 7.4 (d, 2H, Ar), 6.9 (d, 2H, Ar).
5-(3-Nitrobenzylidene)-1,3-thiazolidine-2,4-dione (5f):
Yield: 95 %; m.p.: 188 °C (lit. 187-189 °C [28]); IR (KBr,
H
O
O
Urea-Acetic acid, 1:1,10 mol%
R
O
H
NH
1
νmax, cm–1): 3165, 3052, 2772, 1747, 1695, 1534, 1353; H
+
NH
S
S
R
Microwave
NMR (400 MHz, DMSO-d6): δ = 12.72 (s, 1H, NH), 7.92 (s,
1H, =CH), 8.4 (t, 1H, Ar), 8.28 (dq, 1H, Ar), 7.98 (d, 1H, Ar),
7.7 (t, 1H, Ar); LC-MS: m/z (M +1) calcd. for C10H6N2O4S:
251; found: 251
O
5a-m
O
4
1a-m
Scheme-II: Synthesis of 5-arylidine-2,4-thiazolidinediones
5-(4-Chlorobenzylidene)-1,3-thiazolidine-2,4-dione
(5g): Yield: 92 %; m.p.: 228-229 °C (lit. 228 °C [28]); IR
catalyst from 10 mol % to 20 mol % on the reaction rate as
well as yield of the product.
1
(KBr, νmax, cm–1): 3144, 3048, 2763, 1722, 1609; H NMR
In most of the cases, products (3a-3n, Table-1 and 5a-5l,
Table-2) were identified by previously reported melting points
and spectroscopic methods and newly synthesized compounds
(3c, 3e, 3i, 3k, 3n Table-1 and 5c, 5d, 5h, 5j, 5k, 5l Table-2)
are characterized by IR, 1H NMR and LC-MS. The generality
of this approach has been demonstrated by the condensation
of a wide verity of aromatic aldehydes including electron donating,
electron withdrawing groups and carbocyclic, heterocyclic
rings with active methylene compounds. It was found that in
all cases high yield of product is formed except unsaturated
aldehydes.
(400 MHz, DMSO-d6): δ = 12.57 (s, 1H, NH), 7.74 (s, 1H,
=CH), 7.49-7.55(m, 4H, Ar).
5-(2-Nitrobenzylidene)-1,3-thiazolidine-2,4-dione (5h):
Yield: 92 %; m.p.: 218-220 °C; IR (KBr, νmax, cm–1): 3155,
3056, 2768, 1741, 1682; 1H NMR (400 MHz, DMSO-d6): δ =
12.46 (s, 1H, NH), δ 8.02 (s, 1H, =CH), 8.18 (dq, 1H, Ar),
7.83 (t, 1H, Ar), 7.7-7.6 (m, 2H, Ar).
5-(4-Hydroxy-3-methoxybenzylidene)-1,3-thiazolidine-
2,4-dione (5i): Yield: 90 %; m.p.: 195-197 °C (lit. 194-196
°C [23]); IR (KBr, νmax, cm–1): 3486, 3225, 3018, 2783, 1734,
1677; 1H NMR (400 MHz, DMSO-d6): δ = 12.33 (s, 1H, NH),
9.82 (s, 1H, Ar-OH), 7.67 (s, 1H, =CH), 7.0 (d, 1H, Ar), 7.03
(dq, 1H, Ar), 6.9 (d, 1H, Ar), 3.87 (s, 3H, CH3).
TABLE-1
KNOEVENAGEL CONDENSATION OF ETHYL
CYANOACETATE WITH AROMATIC ALDEHYDES
5-(4-Bromobenzylidene)-1,3-thiazolidine-2,4-dione
(5j):Yield: 90 %; m.p.: 262-264 °C; IR (KBr, νmax, cm–1): 3148,
3052, 2764, 1749, 1722; 1H NMR (400 MHz, DMSO-d6): δ =
12.61 (s, 1H, NH), 7.75 (s, 1H, =CH), 7.6 (d, 2H, Ar), 7.5-7.4
(d, 2H, Ar). LC-MS: m/z (M +1) calcd. for C10H6NO2SBr:
284.9; found: 284.9
Entry
3a
3b
3c
R
Time (s)
50
Yield (%)a,b
C6H5
96
96
92c
3-NO2C6H4
2-ClC6H4
50
60
3-OCH3,4-OHC6H3
3-ClC6H4
60
95
3d
3e
70
98c
92
5-(3-Chlorobenzylidene)-1,3-thiazolidine-2,4-dione
(5k): Yield: 95 %; m.p.: 244-246 °C; IR (KBr, νmax, cm–1):
3166, 3052, 2774, 1745, 1677; 1H NMR (400 MHz, DMSO-
d6): δ = 12.62 (s, 1H, NH), 7.71 (s, 1H, =CH), 7.54 (s, 1H,
Ar), 7.42-7.54 (m, 3H, Ar).
2-Furyl
50
3f
4-ClC6H4
60
94
3g
3h
3i
4-HOC6H4
2-NO2C6H4
4-OCH3C6H4
3,4,5-(OCH3)3C6H2
2-OCH3C6H4
4-Fluoro C6H4
2-Naphthyl
50
90
95c
50
80
90
3j
80
90c
94
3k
3l
5-(2-Methoxybenzylidene)-1,3-thiazolidine-2,4-dione
(5l):Yield: 95 %; m.p.: 260-262 °C; IR (KBr, νmax, cm–1): 3135,
3028, 2769, 1738, 1677; 1H NMR (400 MHz, DMSO-d6): δ =
12.53 (s, 1H, NH), 8.00 (s, 1H, =CH), 7.4 (m, 1H, Ar), 7.3
(dq, 1H,Ar), 7.09-7.04 (m, 2H,Ar); LC-MS: m/z (M +1) calcd.
for C11H9NO3S: 236; found: 236.1.
40
50
94
90c
3m
3n
3k
60
d
–
Ph CH=CH
5-6 min
b
1
aYield of isolated product; Compounds are characterized by IR, H
c
NMR, LC-MS and compared with authentic samples; New com-
pounds; dNo reaction.
RESULTS AND DISCUSSION
The possible mechanism (Scheme-III) for microwave
assisted urea-acetic acid catalyzed Knoevengel condensation,
involves the protonation of carbonyl oxygen of aromatic
aldehydes by acetic acid (III) so increasing electrophilicity of
carbonyl carbon while urea at high energy act as a base reacts
with active methylene compound to forms intermediate (II),
active hydrogen of active methylene is pulled toward the more
electronegative atoms oxygen and nitrogen result in increase
in nucleophilicity of methylene carbon. Then addition of resul-
ting nucleophiles to the carbonyl group of aromatic aldehydes
after dehydration gives the final product.
In this report a simple, efficient, solvent free and rapid method
for microwave-assisted synthesis of ethyl α-cyanocinnamates
(3) and 5-arylidine-2,4-thiazolidinediones (5) is demonstrated.
Various aromatic aldehydes (1) react with active methylene
compounds ethyl cyanoacetate (2) and 1,3-thiazolidine-2,4-
diones (4) catalyzed by urea-acetic acid couple under solvent
free microwave irradiation condition (Schemes I and II). The
reaction was rapid completed within 1-2 min and gave desired
products in good to excellent yield. It was observed that the
reaction does not proceed when performed without urea-acetic
or one of them and no effect on increasing in concentration of

2404 Tryambake
Asian J. Chem.
O
H
−δ
H
O
EWG
CH2
EWG
EWG
+
NH2
H2N
NH2
EWG
NH2
I
II
H
−δ
H
O
EWG
H+
Acetic acid
OH
R
O
+
NH2
+δ
EWG
R
H
NH2
H
III
EWG
O
H
H
+
H+
+
HO
H2N
NH2
EWG
R
IV
-H2O
H
EWG
R
EWG
V
Scheme-III: Possible mechanism for Knoevengel condensation
TABLE-2
KNOEVENGEL CONDENSATION OF 1,3-THIAZOLIDINE-2,4-
DIONES WITH AROMATIC ALDEHYDES
aldehydes improves in terms of simple workup, short reaction
time and good to excellent yield.
Entry
5a
5b
5c
R
Time (min)
1.5
Yield (%)a,b
ACKNOWLEDGEMENTS
C6H5
93
91
90c
87c
86
The author is thankful to University Grants Commission
New Delhi, India for financial assistance and also toThe Director,
SAIF, Panjab University, Chandigarh, India for providing the
spectral analysis.
2-Furyl
1.5
3,4,5-(OCH3)3 C6H2
2-Naphthyl
1.5
2.0
5d
5e
4-HO C6H4
2.0
3-NO2 C6H4
4-Cl C6H4
1.5
95
5f
2.0
92
92c
5g
5h
5i
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