An efficient protocol for the one-pot synthesis of 4-(2-(4-bromophenyl)-1, 2,3-triazol-4-yl)-3,4-dihydropyrimidin-2(1H)-ones/thiones catalyzed by Mg(NO3)2

Article abstract of DOI:10.1002/jhet.517

A series of novel 4-(2-(4-bromophenyl)-1,2,3-triazol-4-yl)-3,4- dihydropyrimidin-2(1H)-ones/thiones were prepared by condensing 2-(4-bromophenyl)-4-formyl-1,2,3-triazole with 1,3-dicarbonyl compound and urea or thiourea using Mg(NO₃)₂

Full text of DOI:10.1002/jhet.517

92
An Efficient Protocol for the One-Pot Synthesis of 4-(2-(4-
Bromophenyl)-1,2,3-triazol-4-yl)-3,4-dihydropyrimidin-2(1H)-
ones/thiones Catalyzed by Mg(NO3)2
Vol 48
Chenjiang Liu,a,b* Xinhai Zhao,b and Yanping Lib
aPhysics and Chemistry Detecting Center, Xinjiang University, Urumqi 830046, China
bKey Laboratory of Petroleum and Gas Fine Chemicals of Ministry of Education, School of
Chemistry and Chemical Engineering, Xinjiang University, Urumqi 830046, China
*E-mail: pxylcj@126.com
Received January 27, 2010
DOI 10.1002/jhet.517
Published online 2 September 2010 in Wiley Online Library (wileyonlinelibrary.com).
A series of novel 4-(2-(4-bromophenyl)-1,2,3-triazol-4-yl)-3,4-dihydropyrimidin-2(1H)-ones/thiones
were prepared by condensing 2-(4-bromophenyl)-4-formyl-1,2,3-triazole with 1,3-dicarbonyl compound
and urea or thiourea using Mg(NO3)2 as an efficient and cheap catalyst. The satisfactory results were
obtained with excellent yields and short reaction time.
J. Heterocyclic Chem., 48, 92 (2011).
INTRODUCTION
liquid [21] have also been utilized to improve and mod-
ify this reaction.
In recent years, dihydropyrimidinones (DHPMs) and
their derivatives have occupied an important position in
natural and synthetic organic chemistry because of their
wide range of biological activities, such as calcium
channel blockers, antiviral, antihypertensive, antifilarial,
and antibacterial [1]. Some of them have been success-
fully used as ala-antagonists and neuropeptide Y (NPY)
antagonists [2]. Several alkaloids which contain the
dihydropyrimidine core unit that have been isolated
from marine sources also showed interesting biological
properties. Most notable among these are the batzella-
dine alkaloids, which were found to be potent as HIV
gp-120-CD4 inhibitors [3].
In the past works, some other groups used conven-
tional aliphatic and substituted aromatic aldehydes as
substrates. Because of the biological properties of tria-
zole derivatives [22,23], in this work, we studied the
possibility to synthesize 4-(2-(4-bromophenyl)-1,2,3-tria-
zol-4-yl)-3,4-dihydropyrimidi-n-2(1H)-ones/thiones by
the Biginelli reaction using 2-(4-bromophenyl)-4-formyl-
1,2,3-triazole instead of the ordinary aromatic aldehydes
as substrates and using Mg(NO3)2 as the catalyst
(Scheme 1). Here, an efficient and simple method for
the synthesis of target compounds is described and none
of them has yet been reported in the literature.
In 1893, Biginelli reported the first synthesis of
DHPM by a simple one-pot condensation reaction of
ethyl acetoacetate, benzaldehyde, and urea [4]. How-
ever, this method often suffers from drawbacks such as
harsh conditions, long reaction times and low yields,
particularly when aliphatic and substituted aromatic
aldehydes are used. Recently, several synthetic proce-
dures for preparing of DHPMs have been reported, such
as the use of a number of Lewis acid catalysts as well
as protic acids including Y(NO3)3ꢀ6H2O [5], SbCl3 [6],
Cu(BF4)2 [7], KAl(SO4)2ꢀ12H2O [8], H3PW12O40 [9],
Sr(OTf)2 [10], Sr(NO3)2 [11], Mg(ClO4)2 [12], InY3
[13], Cu(OTf)2 [14], triphenylphosphine [15], ZrCl4
[16], Ca(NO3)2 [17], H3BO3 [18]. In addition, micro-
wave irradiation [19], ultrasound irradiation [20], ionic
RESULTS AND DISCUSSION
Initially, five nitrate salts were examined in the model
reaction of ethyl acetoacetate, 2-(4-bromophenyl)-4-
formyl-1,2,3-triazole and urea in acetonitrile and
afforded 4-(2-(4-bromophenyl)-1,2,3-triazol-4-yl)-5-etho-
xycarbon-yl-6-methyl-3,4-dihydropyrimidin-2(1H)-one 4a
in various yields (Table 1, entries 1–5). The results show
that the catalytic activity of Mg(NO3)2 was better than
those of the other four nitrate salts. The effect of the sol-
vent on the reaction was also studied and acetonitrile
was found to be the best (Table 1, entries 2, 6–7). The
amount of Mg(NO3)2 was examined next and the results
are summarized in Table 1, entries 2, 8–12. It is clear
C
V
2010 HeteroCorporation

January 2011
An Efficient Protocol for the One-Pot Synthesis of 4-(2-(4-Bromophenyl)-1,2,3-
triazol-4-yl)-3,4-dihydropyrimidin-2(1H)-ones/thiones Catalyzed by Mg(NO3)2
93
Scheme 1. One-pot synthesis of dihydropyrimidin-2(1H)-ones/thiones.
Table 2
Mg(NO3)2-catalyzed one-pot synthesis of the
3,4-dihydropyrimidin-2(1H)ones/thiones 4.a
Product
R
R1
R2
X
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
4-Br-C6H4
4-Br-C6H4
4-Br-C6H4
4-Br-C6H4
4-Br-C6H4
4-Br-C6H4
4-Br-C6H4
4-Br-C6H4
4-Br-C6H4
4-Br-C6H4
4-Br-C6H4
4-Br-C6H4
4-Br-C6H4
4-Br-C6H4
CH3
CH3
CH3
CH3
Ph
OCH2CH3
OCH3
OCH(CH3)2
OC(CH3)3
OCH2CH3
CH3
Ph
OCH2CH3
OCH3
OCH(CH3)2
OC(CH3)3
OCH2CH3
CH3
O
O
O
O
O
O
O
S
from that 10 mol % of Mg(NO3)2 gave the best result
(Table 1, entry 2). However, in the absence of
Mg(NO3)2, the desired product cannot be formed illus-
trating the crucial role of Mg(NO3)2 for the reaction to
proceed (Table 1, entry 8). Hence, the best condition
uses 0.1:1:1:1.5 mole ratio of Mg(NO3)2, ethyl acetoace-
tate, 2-(4-bromophenyl)-4-formyl-1,2,3-triazole and urea
at 80ꢁC using acetonitrile as solvent. To study the scope
of the procedure, a series of DHPMs were synthesized
using the new reaction set-up in satisfactory yields. The
results are listed in Table 2.
CH3
CH3
CH3
CH3
CH3
CH3
Ph
S
S
S
S
CH3
CH3
S
S
Ph
a Reaction conditions: 2-(4-bromophenyl)-4-formyl-1,2,3-triazole (1
mmol), ethylacetoacetate (1 mmol), urea or thiourea (1.5 mmol), cata-
lyst (10 mol), acrylonitrile (6 mL), 80ꢁC.
Spectral examination and microanalysis data of the
products 4a–n confirmed the formation of dihydropyri-
midin ring. The IR spectra of all the products are char-
acterized by the presence of absorbtion bands at 3305–
3171 and 1718–1661 cmꢂ1 corresponding to NH and
C¼¼O functions in the structure. The products 4h–n are
characterized by the presence of absorbtion bands at
at about d 10.35–10.67 ppm assignable to the N1-H pro-
ton on the DHPMs structure. The signals of N3-H pro-
tons appeared as a singlet at about d 7.82–7.96 or d
9.53–9.83 ppm.
1195–1176 cmꢂ1 corresponding to C¼¼S function.
1
In the
HNMR spectra of the products 4a–n,
EXPERIMENTAL
resonances of C-4 methine proton of the ring were seen
as a doublet due to N3-H proton at about d 5.38–5.57
ppm. All products have a one-proton singlet at about d
7.71–8.05 ppm assignable to the triazolyl ring proton.
The products 4a,4c,4d,4e,4f,4g,4h,4i,4n have a one-pro-
ton singlet at about d 9.21–9.36 ppm and other products
The IR spectra are obtained as potassium bromide pellets
with a FTS-40 spectrome-ter (BIO-RAD, U.S.A). The One-
dimensional (1H) and two-dimensional (gHSQC, gHMBC) nmr
spectra are obtained on a Varian Inova-400 (400 MHz) spec-
trometer using CDCl3 or DMSO-d6 as solvent (shown in
details in data part) and tetramethylsilane (TMS) as an internal
standard, chemical shifts are given in ppm. Elemental analyses
(C, H, N) are performed on a Perkin-Elmer Analyzer 2400.
Melting points are determined using a Bu¨chi B-540 instrument
and are uncorrected.
Table 1
Effect of different reaction conditions for condensation of 4a.a
General procedure for preparation synthesis of dihydro-
pyrimidin-2(1H)-ones/thiones (4a–n). A solution of 2-(4-bro-
mophenyl)-4-formyl-1,2,3-triazole (0.25 g, 1 mmole), 1,3-
dicarbonyl compound (1 mmole), urea or thiourea (1.5 mmole)
and Mg(NO3)2 (0.1 mmole) in acetonitrile (6 mL) was heated
with stirring at 80ꢁC in oil bath for an appropriate time (Table
2). The progress of the reaction was monitored by TLC using
ethyl acetate/petroleum ether (1:3). After completion the reac-
tion, the mixture was cooled and the precipitated solid was fil-
tered out, then recrystallized with ethanol to afford pure
product 4a–n. The physicochemical data for the synthesized
compounds are as shown below.
Catalyst
(mol %)
Yield
(%)b
Entry
Catalyst
Conditions
1
2
Ba(NO3)2
Mg(NO3)2
Sr(NO3)2
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
CH3CH2OH
CH3OH
CH3CN
CH3CN
CH3CN
CH3CN
CH3CN
10
10
10
10
10
10
10
none
1
83
94
3
4
86
85
Nd(NO3)3
La(NO3)3
Mg(NO3)2
Mg(NO3)2
Mg(NO3)2
Mg(NO3)2
Mg(NO3)2
Mg(NO3)2
Mg(NO3)2
5
6
91
68
7
30
8
9
none
56
10
11
12
5
15
20
73
79
4-(2-(4-Bromophenyl)-1,2,3-triazol-4-yl)-5-ethoxycarbonyl-6-
methyl-3,4-dihydropyrimidin-2(1H)-one (4a). This compound
82
1
was obtained as white solid, 94% yield, m.p. 250–253ꢁC; H-
a Reaction conditions: 2-(4-bromophenyl)-4-formyl-1,2,3-triazole (1
mmol), ethyl acetoacetate (1 mmol), urea (1.5 mmol) and catalyst in
solvent (6 mL), 80ꢁC.
NMR (DMSO-d6): 9.34 (s, 1H, NH), 7.91 (s, 1H, Tr-H), 7.84
(s, 1H, NH), 7.75–7.89 (dd, 4H, Ar-H), 5.43 (d, 1H, J ¼ 3.2),
4.07 (q, 2H, J ¼ 7.2), 2.25 (s, 3H, CH3), 1.14 (t, 3H, J ¼ 7.2);
IR (KBr) m: 3250, 3180, 2996, 1718, 1665 cmꢂ1; Anal. Calcd
b Isolated yields.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

94
C. Liu, X. Zhao, and Y. Li
Vol 48
(%) for C16H16BrN5O3: C; 47.31, H; 3.97, N; 17.24. found: C;
47.42, H; 3.90, N; 17.36.
NH), 7.91 (s, 1H, Tr-H), 7.73–7.89 (dd, 4H, Ar-H), 5.43 (d,
1H, J ¼ 3.2), 4.05 (q, 2H, J ¼ 7.2), 2.27 (s, 3H, CH3), 1.14
(t, 3H, J ¼ 7.2); IR (KBr) m: 3305, 3196, 2992, 1668, 1187
cmꢂ1; Anal. Calcd (%) for C16H16BrN5O2S: C; 45.51, H; 3.82,
N; 16.58. found C; 45.69, H; 3.86, N; 16.42.
4-(2-(4-Bromophenyl)-1,2,3-triazol-4-yl)-5-methoxycarbonyl-
6-methyl-3,4-dihydropyrimidin-2(1H)-one (4b). This compound
1
was obtained as white solid, 88% yield, m.p. 227–229ꢁC; H-
NMR (DMSO-d6): 10.51 (s, 1H, NH), 9.74 (s, 1H, NH), 7.95
(s, 1H, Tr-H), 7.76–7.90 (dd, 4H, Ar-H), 5.46 (d, 1H, J ¼
3.6), 3.61 (s, 3H, CH3O), 2.31 (s, 3H, CH3); IR (KBr) m:
3302, 3192, 2979, 1710, 1661 cmꢂ1; Anal. Calcd (%) for
C15H14BrN5O3: C; 45.94, H; 3.60, N ;17.86. found: C; 46.08,
H; 3.66, N; 18.02.
4-(2-(4-Bromophenyl)-1,2,3-triazol-4-yl)-5-methoxycarbonyl-
6-methyl-3,4-dihydropyrimidin-2(1H)-thione (4i). This com-
pound was obtained as light yellow solid, 97% yield, m.p.
265–266ꢁC; 1H-NMR (DMSO-d6): 9.36 (s, 1H, NH), 7.92 (s,
1H, Tr-H), 7.86 (s, 1H, NH), 7.74–7.90 (dd, 4H, Ar-H), 5.42
(d, 1H, J ¼ 3.6), 3.60 (s, 3H, CH3O), 2.25 (s, 3H, CH3); IR
(KBr) m: 3278, 3185, 2992, 1686, 1176 cmꢂ1; Anal. Calcd (%)
for C15H14BrN5O2S: C; 44.13, H; 3.46, N; 17.15. found C;
43.92, H; 3.42, N; 17.36.
4-(2-(4-Bromophenyl)-1,2,3-triazol-4-yl)-6-methyl-5-(iso-pro-
pyloxycarbonyl)-3,4-dihydropyrimidin-2(1H)-one (4c). This
compound was obtained as muddy color solid, 83% yield, m.p.
218–221ꢁC; 1H-NMR (DMSO-d6): 9.30 (s, 1H, NH), 7.90 (s,
1H, Tr-H), 7.83 (s, 1H, NH), 7.75–7.89 (dd, 4H, Ar-H), 5.42
(d, 1H, J ¼ 3.2), 4.88 (m, 1H, CH), 2.25 (s, 3H, CH3), 1.19
(d, 3H, J ¼ 6.4), 1.06 (d, 3H, J ¼ 6.0); IR (KBr) m: 3250;
4-(2-(4-Bromophenyl)-1,2,3-triazol-4-yl)-6-methyl-5-(iso-pro-
pyloxycarbonyl)-3,4-dihydropyrimidin-2(1H)-thione (4j). This
compound was obtained as yellow solid, 86% yield, m.p. 288–
1
290ꢁC; H-NMR (DMSO-d6): 10.47 (s, 1H, NH), 9.71 (s, 1H,
3181; 2980; 1716; 1676 cmꢂ1
;
Anal. Calcd (%) for
NH), 7.93 (s, 1H, Tr-H), 7.76–7.90 (dd, 4H, Ar-H), 5.46 (d,
1H, J ¼ 3.6), 4.89 (m, 1H, CH), 2.31 (s, 3H, CH3), 1.19
(d, 3H, J ¼ 6.4), 1.05 (d, 3H, J ¼ 6.0); IR (KBr) m: 3280,
C17H18BrN5O3: C; 48.58, H; 4.32, N; 16.66. found: C; 48.43,
H; 4.38, N; 16.52
4-(2-(4-Bromophenyl)-1,2,3-triazol-4-yl)-5-(tert-butyloxycarb-
ony)-6-methyl-3,4-dihydropyrimidin-2(1H)-one (4d). This com-
pound was obtained as white solid, 88% yield, m.p. 255–
256ꢁC; 1H-NMR (DMSO-d6): 9.21 (s, 1H, NH), 7.90 (s, 1H,
Tr-H), 7.87 (s, 1H, NH), 7.76–7.88 (dd, 4H, Ar-H), 5.38 (d,
1H, J ¼ 3.2), 2.22 (s, 3H, CH3), 1.35 (s, 9H, (CH3)3C); IR
(KBr) m: 3279, 3191, 2975, 1712, 1672 cmꢂ1; Anal. Calcd (%)
for C18H20BrN5O3: C; 49.78, H; 4.64, N; 16.13. found: C;
49.63, H; 4.60, N; 16.26.
3198, 2975, 1694, 1189 cmꢂ1
; Anal. Calcd (%) for
C17H18BrN5O2S: C; 46.80, H; 4.16, N; 16.05. found C; 46.59,
H; 4.10, N; 16.21.
4-(2-(4-Bromophenyl)-1,2,3-triazol-4-yl)-5-(tert-butyloxy-
carbony)-6-methyl-3,4-dihydropyrimidin-2(1H)-thione (4k). This
compound was obtained as white solid, 98% yield, m.p. 210–
1
213ꢁC; H-NMR (DMSO-d6): 10.38 (s, 1H, NH), 9.65 (s, 1H,
NH), 7.91 (s, 1H, Tr-H), 7.77–7.90 (dd, 4H, Ar-H), 5.41 (d,
1H, J ¼ 4.0), 2.27 (s, 3H, CH3), 1.39 (s, 9H, (CH3)3C); IR
(KBr) m: 3265, 3205, 2985, 1690, 1190 cmꢂ1; Anal. Calcd (%)
for C18H20BrN5O2S: C; 48.01, H; 4.48, N; 15.55. found C;
48.20, H; 4.42, N; 15.69.
4-(2-(4-Bromophenyl)-1,2,3-triazol-4-yl)-5-ethoxycarbonyl-6-
phenyl-3,4-dihydropyrimidin-2(1H)-one (4e). This compound
1
was obtained as white solid, 82% yield, m.p. 154–157ꢁC; H-
NMR (DMSO-d6): 10.35 (s, 1H, NH), 9.53 (s, 1H, NH), 7.95
(s, 1H, Tr-H), 7.53–7.97 (m, 9H, Ar-H), 5.41 (d, 1H, J ¼ 3.2),
4.25 (q, 2H, J ¼ 7.2), 1.19 (t, 3H, J ¼ 7.2); IR (KBr) m: 3255,
4-(2-(4-Bromophenyl)-1,2,3-triazol-4-yl)-5-ethoxycarbonyl-6-
phenyl-3,4-dihydropyrimidin-2(1H)-thione (4l). This com-
pound was obtained as yellow solid, 81% yield, m.p. 219–
220ꢁC; 1H-NMR (DMSO-d6): 10.67 (s, 1H, NH), 9.83 (s,
1H, NH), 8.06 (s, 1H, Tr-H), 7.78–7.94 (dd, 4H, Ar-H),
7.34–7.45 (m, 5H, Ar-H), 5.56 (d, 1H, J ¼ 4.0), 3.80 (q, 2H,
J ¼ 7.2), 0.77 (t, 3H, J ¼ 7.2); IR (KBr) m: 3259, 3181,
3190, 2985, 1708, 1680 cmꢂ1
; Anal. Calcd (%) for
C21H18BrN5O3: C; 53.86, H; 3.87, N; 14.95, found: C; 54.03,
H; 3.81, N; 15.06.
5-Acetyl-4-(2-(4-bromophenyl)-1,2,3-triazol-4-yl)-6-methyl-
3,4-dihydropyrimidin-2(1H)-one (4f). This compound was
obtained as pink solid, 87% yield, m.p. 298–300ꢁC; 1H-NMR
(DMSO-d6): 9.32 (s, 1H, NH), 7.93 (s, 1H, NH), 7.87 (s, 1H,
Tr-H), 7.75–7.90 (dd, 4H, Ar-H), 5.52 (d, 1H, J ¼ 3.6), 2.28
(s, 3H, CH3CO), 2.26 (s, 3H, CH3); IR (KBr) m: 3260, 3171,
2992, 1706, 1688 cmꢂ1; Anal. Calcd (%) for C15H14BrN5O2:
C; 47.89, H; 3.75, N; 18.62. found: C; 48.03, H; 3.79, N;
18.73.
5-Acetyl-4-(2-(4-bromophenyl)-1,2,3-triazol-4-yl)-6-phenyl-
3,4-dihydropyrimidin-2(1H)-one (4g). This compound was
obtained as light yellow solid, 86% yield, m.p. 271–273ꢁC;
1H-NMR (DMSO-d6): 9.34 (s, 1H, NH), 7.98 (s, 1H, Tr-H),
7.96 (s, 1H, NH), 7.74–7.88 (dd, 4H, Ar-H), 7.45–7.59 (m,
5H, Ar-H), 5.57 (d, 1H, J ¼ 3.6),1.66 (s, 3H, CH3CO); IR
(KBr) m: 3290, 3249, 2961, 1714, 1675 cmꢂ1; Anal. Calcd (%)
for C20H16BrN5O2: C; 54.81, H; 3.68, N; 15.98. found: C;
54.66, H; 3.75, N; 16.12
2975, 1666, 1195 cmꢂ1
;
Anal. Calcd (%) for
C21H18BrN5O2S: C; 52.07, H; 3.75, N; 14.46. found C;
52.23, H; 3.79, N; 14.59.
5-Acetyl-4-(2-(4-bromophenyl)-1,2,3-triazol-4-yl)-6-methyl-
3,4-dihydropyrimidin-2(1H)-thione (4m). This compound was
1
obtained as white solid, 98% yield, m.p. 300–303ꢁC; H-NMR
(DMSO-d6): 10.45 (s, 1H, NH), 9.83 (s, 1H, NH), 7.89 (s, 1H,
Tr-H), 7.76–7.89 (dd, 4H, Ar-H), 5.56 (d, 1H, J ¼ 4.0), 2.34
(s, 3H, CH3CO), 2.29 (s, 3H, CH3); IR (KBr) m: 3286, 3206,
2992, 1675, 1184 cmꢂ1; Anal. Calcd (%) for C15H14BrN5OS:
C; 45.93, H; 3.60, N; 17.85. found C; 46.14, H; 3.55, N;
17.94.
5-Acetyl-4-(2-(4-bromophenyl)-1,2,3-triazol-4-yl)-6-phenyl-
3,4-dihydropyrimidin-2(1H)-thione (4n). This compound was
obtained as yellow solid, 94% yield, m.p. 268–271ꢁC; 1H-
NMR (DMSO-d6): 9.34 (s, 1H, NH), 7.98 (s, 1H, Tr-H), 7.96
(s, 1H, NH), 7.74–7.87 (dd, 4H, Ar-H), 7.45–7.59 (m, 5H, Ar-
H), 5.57 (d, 1H, J ¼ 3.2), 1.66 (s, 3H, CH3); IR (KBr) m:
3257, 3177, 2992, 1695, 1179 cmꢂ1; Anal. Calcd (%) for
C20H16BrN5OS: C; 52.87, H; 3.55, N; 15.41. found C; 52.69,
H; 3.52, N; 15.57.
4-(2-(4-Bromophenyl)-1,2,3-triazol-4-yl)-5-ethoxycarbonyl-6-
methyl-3,4-dihydropyrimidin-2(1H)-thione (4h). This com-
pound was obtained as white solid, 91% yield, m.p. 206–
208ꢁC; 1H-NMR (DMSO-d6): 9.33 (s, 1H, NH), 7.94 (s, 1H,
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

January 2011
An Efficient Protocol for the One-Pot Synthesis of 4-(2-(4-Bromophenyl)-1,2,3-
triazol-4-yl)-3,4-dihydropyrimidin-2(1H)-ones/thiones Catalyzed by Mg(NO3)2
95
[10] Su, W. K.; Li, J. J.; Zheng, Z. G.; Shen, Y. C. Tetrahedron
Lett 2005, 46, 6037.
Acknowledgment. The authors thank the National Natural Sci-
ence Foundation of China (No. 20662009) for their support.
[11] Liu, C. J.; Wang, J. D.; Li, Y. P. J Mol Catal A: Chem
2006, 258, 367.
REFERENCES AND NOTES
[12] Zhang, X. L.; Li, Y. P.; Liu, C. J. J Mol Catal A: Chem
2006, 253, 207.
[1] (a) Kappe, C. O. Eur J Med Chem 2000, 35, 1043; (b)
Kappe, C. O.; Shishkin, O. V.; Uray, G.; Verdino, P. Tetrahedron
2000, 56, 1859; (c) Singh, B. K.; Mishra, M.; Saxena, N.; Yadav,
G. Eur J Med Chem 2008, 43, 2717; (d) Deshmukh, M. B.; Sal-
unkhe, S. M.; Patil, D. R.; Anbhule, P. V. Eur J Med Chem 2009,
44, 2651.
[13] Fu, N. Y.; Yuan, Y. F.; Pang, M. L.; Wang, J. T.; Peppe,
C. J Organomet Chem 2003, 672, 52.
[14] Paraskar, A. S.; Dewkar, G. K.; Sudalai, A. Tetrahedron
Lett 2003, 44, 3305.
[15] Debache, A.; Amimour, M.; Belfaitah, A.; Rhouati, S.; Car-
boni, B. Tetrahedron Lett 2008, 49, 6119.
[2] Atwal, K. S.; Rovnyak, G. C.; O’Reilly, B. C.; Schwartz, J.
J Org Chem 1989, 54, 5898.
[16] Kumar, H.; Parmar, A. Ultrason Sonochem 2008, 15, 129.
[17] Abdelmadjid, D.; Raouf, B.; Radia, T.; Ali, B.; Salah, R.;
Bertrand, C. Chin J Chem 2008, 26, 2112.
[3] Patil, A. D.; Kumar, N. V.; Kokke, W. C.; Bean, M. F.
J Org Chem 1995, 60, 1182.
[18] Tu, S.-J.; Zhu, X.-T.; Fang, F.; Zhang, X.-J.; Zhu, S.-L.; Li,
T.-J.; Shi, D.-Q.; Wang, X.-S.; Ji, S.-J. Chin J Chem 2005, 23, 596.
[19] Zhang, M.; Li, Y.-Q.; Zhou, M.-Y. Chin J Chem 2006, 24,
282.
[4] Biginelli, P. Gazz Chim Ital 1893, 23, 360.
[5] Nandurkar, N. S.; Bhanushali, M. G.; Bhor, M. D.; Bhan-
age, B. M. J Mol Catal A: Chem 2007, 271, 14.
[6] Cepanec, I.; Litvic, M.; Litvic, M. F.; Gru¨ngold, I. Tetrahe-
dron 2007, 63, 11822.
[20] Memarian, H. R.; Senejani, M. A. Ultrason Sonochem
2008, 15, 110.
[7] Kamal, A.; Krishnaji, T.; Azhar, M. A. Catal Commun
2007, 8, 1929.
[21] Yadav, L. D. S.; Rai, A.; Rai, V. K.; Awasthi, C. Tetrahe-
dron 2008, 64, 1420.
[8] Azizian, J.; Mohammadi, A. A.; Karimi, A. R.; Mohamma-
dizadeh, M. R. Appl Catal A: Gen 2006, 300, 85.
[9] Amini, M. M.; Shaabani, A.; Bazgir, A. Catal Commun
2006, 7, 843.
[22] Kupper, T.; Bucheli, T. D.; Brndli, R. C.; Ortelli, D.; Edder,
P. Bioresour Technol 2008, 99, 7988.
[23] Paul, K. V.; Loganathan, D. Tetrahedron Lett 2008, 49, 6356.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet