An efficient synthesis of new 3,4-dihydropyrimidin- 2(1H)-ones incorporating a phenyl moiety at C-5 and C-6 catalyzed by TMSCl and Co(OAc)2.4H2O

Article abstract of DOI:10.1080/10426500802341499

New 3,4-dihydropyrimidin-2-ones having a phenyl moiety at C-5 and C-6 have been prepared by a microwave-assisted Biginelli-like reaction by a three-component, one-pot condensation of an aromatic aldehyde, deoxybenzoin and urea, or thiourea using TMSCl and

Full text of DOI:10.1080/10426500802341499

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Phosphorus, Sulfur, and Silicon
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An Efficient Synthesis of
New 3,4-Dihydropyrimidin-
2(1H)-ones Incorporating a
Phenyl Moiety at C-5 and
C-6 Catalyzed by TMSCl and
Co(OAc)2.4H2O
Hassan Kefayati a , Maryam Fakhriyannejad a & Ali A.
Mohammadi b
a Department of Chemistry, Islamic Azad University,
Bandar Anzali Branch, Iran
b Department of Chemistry, Shahid Beheshti
University, Tehran, Iran
Version of record first published: 22 Jun 2009.
To cite this article: Hassan Kefayati , Maryam Fakhriyannejad & Ali A. Mohammadi
(2009): An Efficient Synthesis of New 3,4-Dihydropyrimidin- 2(1H)-ones Incorporating
a Phenyl Moiety at C-5 and C-6 Catalyzed by TMSCl and Co(OAc)2.4H2O, Phosphorus,
Sulfur, and Silicon and the Related Elements, 184:7, 1796-1804
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Phosphorus, Sulfur, and Silicon, 184:1796–1804, 2009
Copyright © Taylor & Francis Group, LLC
ISSN: 1042-6507 print / 1563-5325 online
DOI: 10.1080/10426500802341499
An Efficient Synthesis of New 3,4-Dihydropyrimidin-
2(1H)-ones Incorporating a Phenyl Moiety at C-5 and C-6
Catalyzed by TMSCl and Co(OAc)2.4H2O
Hassan Kefayati,1 Maryam Fakhriyannejad,1
and Ali A. Mohammadi2
1Department of Chemistry, Islamic Azad University, Bandar Anzali
Branch, Iran
2Department of Chemistry, Shahid Beheshti University, Tehran, Iran
New 3,4-dihydropyrimidin-2-ones having a phenyl moiety at C-5 and C-6 have been
prepared by a microwave-assisted Biginelli–like reaction by a three-component,
one-pot condensation of an aromatic aldehyde, deoxybenzoin and urea, or thiourea
using TMSCl and Co(OAc) .4H O as an efficient Lewis acid catalyst.
2
2
Keywords Biginelli–like reaction; Co(OAc)2.4H2O; 3,4-dihydropyrimidin-2-one;
microwave-assisted; TMSCl
INTRODUCTION
Many aryl-substituted 3,4-dihydropyrimidin-2-ones (DHPMs) and
their derivatives are an important class of compounds in the field of
drugs and pharmaceuticals.1 They are found to exhibit a wide range
of biological activities2 such as antibacterial, antiviral, antitumor, and
anti-inflammatory properties. Most of the DHPMs and their derivatives
are medicinally important as calcium channel blockers, antihyperten-
sive agents, X1a-antagonists, and HIV agents.3 The biological activities
of some marine alkaloids isolated recently have been attributed to the
presence of dihydropyrimidinone moiety.4 The first reported synthe-
sis of 3,4-dihydropyrimidin-2(1H)-ones using a multicomponent reac-
tion milieu was described by Biginelli in 1893.5 The Biginelli reaction
consists of a three-component, one-pot condensation of β-ketoesters,
with aldehydes and urea under strongly acidic conditions to afford 3,4-
dihydropyrimidinones having an esters moiety at C-5 and an alkyl sub-
stituent at C-6. However, the yields of the products were very low, just
20%–50%. From then on, many new techniques, such as microwave-
assisted synthesis techniques,6 ionic liquids,7 ultrasound irradiation,8
and solvent free techniques,9 and many new catalysts such as
1796

Efficient Synthesis of New 3,4-Dihydropyrimidin-2(1H)-ones
1797
polyphosphonate ester (PPE),10 montmorillonite,11 InCl3,12 lanthanide
triflate,13 cericammonium nitrate,14 BiCl3,15 LiClO4,16 TMSCl,17–18
and Co(II),19 etc., were used to improve this transformation.
The first Biginelli–like reaction, reported by Wang et al.,20 was con-
ducted in CH3CN by using aldehydes, ketones, and urea, which re-
markably broadened the Biginelli reaction. In recent years, several
synthetic procedures for preparing DHPMs via a Biginelli–like re-
action have been reported. In spite of their potential utility, some
of these methods involve long reaction times (12 h), stoichiometric
amounts of catalysts, and unsatisfactory yields. Furthermore, the scope
of substrates was limited to aromatic aldehydes, acetophenone, and
urea.21–22
Following our previous work about the Biginelli reaction,23,24 we
would like to report, for the first time, a simple approach to the
Biginelli–like reaction via a three-component cyclocondensation of an
aromatic aldehyde, ketone or β-ketoester, urea or thiourea as sub-
strates, and Co(OAc)2.4H2O and chlorotrimethylsilane (TMSCl) as cat-
alysts under microwave irradiation, which is an efficient preparation
of new 3,4-dihydropyrimidin-2(1H)-ones having phenyl moiety at C-5
and C-6.
RESULTS AND DISCUSSION
We first began to study the reaction involving 3-methoxy benzaldehyde
(5 mmol), deoxybenzoin (5 mmol), and urea (15 mmol) by examining
the type of catalysts (Scheme 1). Many catalysts or promoters, such as
Zn(OAc)2, FeCl3, FeCl3.6H2O, AlCl3.6H2O, and Co(OAc)2.4H2O, were
used to explore the reaction conditions (Table I). From these results, we
found that most of the Lewis acids could promote the reaction, but the
yields were not very high. In comparison with other catalysts, the use of
0.25 mmol of Co(OAc)2.4H2O could make the yield reach 69% under the
microwave power (P) of 300 W and the irradiation time of 7 min. How-
ever, we found that the addition of TMSCl accelerated the Biginelli–
like reaction and gave a good result. For example, the TMSCl-mediated
Biginelli–like reaction of deoxybenzoine, 3-methoxybenzaldehyde, and
urea gave the corresponding product in high yield. From the result,
we concluded that the mixture of Co(OAc)2.4H2O and TMSCl is the
best catalyst for this reaction. The amount of Co(OAc)2.4H2O and TM-
SCl was further examined, and the results are summarized in Table
I. It could be seen that 0.25 mmol of Co(OAC)2.4H2O and 2.5 mmol of
TMSCl gave the best result in this reaction.

1798
H. Kefayati et al.
TABLE I Effects of the Type and the Amount of
Catalysts on the Formation of 4a∗
Entry
Catalysis (mmol)
TMSCI (mmol)
Yield (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
Zn(OAc)2 (0.25)
Zn(OAc)2 (1)
Zn(OAc)2 (1.5)
Co(OAc)2. 4H2O (0.25)
Co(OAc)2. 4H2O (1)
Zn(OAc)2 (1)
Zn(OAc)2 (2.5)
Co(OAc)2. 4H2O (1)
Co(OAc)2. 4H2O (0.25)
Co(OAc)2. 4H2O (0.25)
Co(OAc)2. 4H2O (0.25)
Co(OAc)2. 4H2O (.25)
FeCl3 (1)
FeCl3. 6H2O (1)
AlCl3. 6H2O (1)
–
—
—
—
—
—
2.5
2.5
2.5
2.5
5
7.5
9
5
5
5
60
73
78
69
64
69
54
82
91
60
60
58
77
78
74
52
57
61
45
2.5
5
7.5
9
–
–
–
∗Reaction condition: 3-methoxybenzaldehyde 5 mmol, deoxybenzoin
5 mmol, urea 15 mmol, P = 300 W, DMF.
Based on the above optimized result, we further examined the effect
of a stoichiometric amount of urea, type of solvent, microwave power,
and the irradiation time on the Biginelli–like reaction, involving de-
oxybenzoin, 3-methoxybenzaldehyde, and urea to afford DHPM 4a, as
shown in Scheme 1.
It could be found that with the increase of the microwave power
from 80 to 300 W, the yield of 4a increased to 91% when the irradiation
time was 7 min. However, with the microwave power of 300 W, when
MeO
O
O
MeO
catalysis, solvent
+
NH
+
H2N
NH2
microwave
irradiation
N
H
O
CHO
2
3
4a
1
SCHEME 1 Microwave-assisted Biginelli–like reaction by various catalysts.

Efficient Synthesis of New 3,4-Dihydropyrimidin-2(1H)-ones
1799
TABLE II Effects of the Microwave Power and the Irradiation
Time on the Formation of 4a∗
Entry
Time (min)
P(W)
Yield (%)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
10
15
2
3
4
5
6
7
8
10
14
2
3
4
80
150
300
300
300
300
300
300
300
300
300
450
450
450
650
650
—
10
60
72
80
80
89
91
88
87
32
45
30
—
15
—
1
2
∗Reaction condition: 3-methoxybenzaldehyde 5 mmol, deoxybenzoin 5
mmol, urea 15 mmol, Co(OAC)2.4H2O 0.25 mmol, and TMSCl 2.5 mmol, DMF.
we increased the microwave irradiation time, the yield of 4a increased
first, then showed a slight decrease when the time was more than 7
min. So optimized microwave power and the irradiation time were 300
W and 7 min, respectively (Table II).
In order to examine the substrate scope of Biginelli–like reaction, we
examined the reacation of various ketones, aromatic aldehyde, and urea
or thiourea under the above optimized reaction condition (Scheme 2).
R1
X
O
Co(OAC)2 .4H2O
R3
TMSCl, DMF
R3
R1
NH
microwave
NH2
irradiation
R2
H2N
+
+
R2
N
H
X
CHO
X=O, S
6
4a-s
5
7
SCHEME 2 Microwave-assisted Biginelli–like reaction by various aromatic
aldehydes, ketone or β-ketoester, and urea or thiourea.

1800
H. Kefayati et al.
TABLE III Cyclocondensation of Aromatic Aldehydes, Ketone or
β-Ketoester, and Urea or Thiourea∗
Found
Reported
t
t
Yield
Yield
Entry
R1
R2
R3
X
mp (◦C) (time) (%)
mp (◦C)
(time) (%)
4a
4b
4c
4d
4e
4f
4g
4h
4i
4j
4k
4l
4m
4n
4o
4p
4q
4r
4s
3-OMe Ph Ph
3-Cl Ph Ph
3-NO2 Ph Ph
O
O
O
O
O
S
S
S
S
O
O
O
O
O
O
O
O
S
191–193
199–201
222–224
256–258
240–242
259–261
241–243
239–241
263–265
228–230
218–220
265–266
201–202
224–226
191–192
200–202
217–219
204–205
203–204
7
7
7
7
7
7
7
7
7
7
7
7
6
6
6
6
6
4
4
91
82
96
91
85
97
98
95
95
80
90
95
94
97
95
91
90
96
94
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
4-Cl
H
H
Ph Ph
Ph Ph
Ph Ph
Ph Ph
4-Me
3-OMe Ph Ph
3-Cl
3-Cl
H
4-Cl
H
Ph Ph
Me Me
–
–
–
3 h
–
ph
ph
H
H
218–219[21]
267–269[22] 8 min
87
93
90
80
93
84
85
86
53
Me COOEt
200–202[25]
225–227[25]
192–194[24]
199–201[25]
216–218[25]
205–206[25]
203–205[26]
3 h
3 h
4 h
3 h
3 h
3 h
3 h
3-NO2 Me COOEt
3-Cl Me COOEt
4-OMe Me COOEt
2-Cl
H
Me COOEt
Me COOEt
3-NO2 Me COOEt
S
∗Reaction condition: aromatic aldehyde 5 mmol; ketone or β-ketoester 5 mmol;
urea15 mmol or thiourea 12 mmol, Co(OAc)2.4H2O 0.25 mmol and TMSCl 2.5 mmol,
DMF, P = 300 W.
The results are shown in Table III, entries 4a–l. From the result, we
could see that all reactions afforded the corresponding DHPMs in mod-
erate to high yield. Promoted by this success and in order to compare
with other methods,21–26 we extended this reaction of urea or thiourea
with various aldehydes and ethylacetoacetate under similar conditions
and obtained the respective 3,4-dihydropyrimidin-2(1H)-ones 4m–s in
good to excellent yields. The optimized results are summarized in Table
III.
In conclusion, an efficient and high-yield protocol for the synthesis
of new 3,4-dihydropyrimidin-2(1H)-ones involving a three-component,
one-pot condensation of an aromatic aldehyde, ketones or β-ketoester,
and urea or thiourea using Co(OAc)2.4H2O and TMSCl as an efficient
Lewis acid catalyst under microwave irradiation was developed and
compared with other methods. Short reaction time, high yield, simple

Efficient Synthesis of New 3,4-Dihydropyrimidin-2(1H)-ones
1801
product isolation procedure, and the use of low amount of catalyst were
the advantages of this protocol.
EXPERIMENTAL
All reagents were purchased from Merck and Fluka and used with-
out further purification. All melting points were measured on an Elec-
trothermal IA 9100 apparatus and are uncorrected. IR spectra were
recorded on a Shimadzu FT-IR 8600 instrument. 1H and 13C NMR
spectra were recorded in DMSO using TMS as an internal standard
on a Bruker DRX-300 Avance spectrometer at 300 MHz. Elemental
analyses were carried out on a Thermo Finnigan Flash EA 1112 series
instrument. All products are new compounds, which were identified by
IR, 1H, and 13C NMR spectral data.
General Procedure
A mixture of an aromatic aldehyde 5 (5 mmol), ketone or β-ketoester
6 (5 mmol), urea (15 mmol) or thiourea 7 (12 mmol), Co(OAc)2.4H2O
(0.25 mmol), TMSCl (2.5 mmol), and DMF (5 mL) contained in a 100
mL beaker was placed in the microwave oven. The beaker was covered
with a stemless funnel and subjected to irradiation conditions as shown
in Table III. After the reaction was complete, it was allowed to cool to
room temperature. Then distilled water (30 mL) was added into the
beaker and stirred for several minutes. The precipitate thus obtained
was filtered off. The crude product purified by recrystallization from
ethanol and dried to give powder compounds 4a–s.
3,4-Dihydro-4-(3-methoxyphenyl)-5,6-diphenylpyrimidin-2(1H)-
one 4a
White powder; mp 191–193◦C; IR (KBr) νmax: 3211, 3076, 2925, 1664,
1595, 1485 cm−1; 1H NMR(DMSO) δ: 3.70 (s, 3H, OMe), 5.12 (s, 1H, CH),
6.81–7.28 (m, 14H, Ar-H), 7.53 (s, 1H, NH), 8.67 (s, 1H, NH); 13C NMR
(DMSO) δ: 54.88, 59.18, 109.36, 112.62, 112.84, 119.06, 125.82, 127.70,
128.01, 128.13, 129.25, 129.28, 129.68, 134.79, 134.95, 138.02, 145.29,
153.18, 159.38. Anal. Calcd. For C23H20N2O2 (356.42): C, 77.51; H, 5.66;
N, 7.86. Found: C, 77.40; H, 5.61; N, 7.88.
3,4-Dihydro-4-(3-chlorophenyl)-5,6-diphenylpyrimidin-2(1H)-
one 4b
White powder; mp 199–201◦C; IR (KBr) νmax: 3220, 3091, 2918, 1689,
1
1595, 1471 cm−1; H NMR(DMSO) δ: 5.19 (s, 1H, CH), 6.78-7.38 (m,

1802
H. Kefayati et al.
14H, Ar-H), 7.53 (s, 1H, NH), 8.66 (s, 1H, NH); 13C NMR (DMSO) δ:
58.75, 108.94, 125.55, 125.94, 126.86, 127.39, 127.77, 127.99, 128.18,
129.26, 129.28, 130.51, 133.07, 134.75, 135.03, 137.63, 146.20, 152.85.
Anal. Calcd. For C22H17ClN2O (360.84): C, 73.23; H, 4.75; N, 7.76.
Found: C, 73.31; H, 4.69; N, 7.85.
3,4-Dihydro-4-(3-nitrophenyl)-5,6-diphenylpyrimidin-2(1H)-
one 4c
Yellow powder; mp 222–224◦C; IR (KBr) νmax: 3232, 3097, 2928, 1702,
1
1651, 1530 cm−1; H NMR(DMSO) δ: 5.41 (s, 1H, CH), 6.79-8.13 (m,
14H, Ar-H), 8.19 (s, 1H, NH), 8.79 (s, 1H, NH); 13C NMR (DMSO) δ:
58.50, 108.66, 121.65, 122.48, 126.06 127.87, 128.05, 128.29, 129.31,
130.26, 133.69, 134.66, 135.44, 137.38, 145.87, 147.91, 152.80. Anal.
Calcd. For C22H17N3O3 (371.39): C, 71.15; H, 4.61; N, 11.31. Found: C,
71.22; H, 4.57, N, 11.25.
3,4-dihydro-4-(4-chlorophenyl)-5,6-diphenylpyrimidin-2(1H)-
one 4d
White powder; mp 256–258◦C; IR (KBr) νmax: 3211, 3060, 2906,
1690, 1596, 1490 cm−1 1H NMR(DMSO) δ: 5.20 (s, 1H, CH), 6.79-
;
7.42 (m, 14H, Ar-H), 7.56 (s, 1H, NH), 8.70 (s, 1H, NH); 13C NMR
(DMSO) δ: 59.55, 110.03, 126.83, 128.69, 128.89, 129.08, 129.47, 129.78,
130.2, 132.86, 135.70, 135.74, 138.66, 143.71, 153.82. Anal. Calcd. For
C22H17ClN2O (360.84): C, 73.23; H, 4.75; N, 7.76. Found: C, 73.27; H,
4.71; N, 7.69.
3,4-Dihydro-4,5,6-triphenylpyrimidin-2(1H)-one 4e
White powder; mp 240–242◦C; IR (KBr) νmax: 3220, 3082, 2918,
1699, 1595, 1481 Cm−1 1H NMR(DMSO) δ: 5.15 (s, 1H, CH), 6.78-
;
7.38 (m, 15H, Ar-H), 7.53 (s, 1H, NH), 8.66 (s, 1H, NH); 13C NMR
(DMSO) δ: 59.39, 109.53, 125.79, 126.93, 127.40, 127,65, 127,93, 128,06,
128.51, 129.27, 134.61, 134.92, 137.99, 143.81, 153.08. Anal. Calcd. For
C22H18N2O (326.39): C, 80.96; H, 5.56; N, 8.58. Found: C, 80.89; H, 5.54;
N, 8.61.
3,4-dihydro-4,5,6-triphenylpyrimidin-2(1H)-thione 4f
White powder; mp 259–261◦C; IR (KBr) νmax: 3168, 3100, 2972, 1645,
1
1568, 1479 cm−1; H NMR(DMSO) δ: 5.13 (s, 1H, CH), 6.78–7.39 (m,
15H, Ar-H), 9.33 (s, 1H, NH), 9.95 (s, 1H, NH); 13C NMR (DMSO) δ:
58.82, 111.17, 126.31, 127.09, 127.80, 127.86, 128.00, 128.42, 128.72,
128.97, 129.59, 133.42, 133.81, 137.22, 142.42, 173.56. Anal. Calcd. For

Efficient Synthesis of New 3,4-Dihydropyrimidin-2(1H)-ones
1803
C22H18N2S (342.46): C, 77.16; H, 5.30; N, 8.18. Found: C, 77.09; H, 5.32;
N, 8.21.
3,4-Dihydro-4-(4-metylphenyl)-5,6-diphenylpyrimidin-2(1H)-
thione 4g
White powder; mp 241–243◦C; IR (KBr) νmax: 3209, 3050, 2943, 1649,
1569, 1479 cm−1; 1H NMR(DMSO) δ: 2.28 (s, 3H, CH3), 5.07 (s, 1H, CH),
6.79–7.28 (m, 14H, Ar-H), 9.28 (s, 1H, NH), 9.91 (s, 1H, NH); 13C NMR
(DMSO) δ: 20.65, 58.59, 111.23, 126.28, 127.03, 127.79, 128.00, 128.40,
129.27, 129.59, 133.33, 133.85, 137.10, 137.31, 139.54, 173.46. Anal.
Calcd. For C23H20N2S (356.48): C, 77.49; H, 5.65; N, 7.86. Found: C,
77.53; H, 5.62; N, 7.81.
3,4-Dihydro-4-(3-methoxyphenyl)-5,6-diphenylpyrimidin-2(1H)-
thione 4h
White powder; mp 239–241◦C; IR (KBr) νmax: 3192, 3091, 2954, 2842,
1
1639, 1558, 1461 cm−1; H NMR(DMSO) δ: 3.71 (s, 3H, OCH3), 5.10
(s, 1H, CH), 6.80–7.31 (m, 14H, Ar-H), 9.32 (s, 1H, NH), 9.96 (s, 1H,
NH); 13C NMR (DMSO) δ: 54.95, 58.68, 111.00, 112.97, 113.05, 119.16,
126.34, 127.84, 128.07, 128.46, 128.96, 129.57, 129.87, 133.56, 133.83,
137.24, 143.84, 159.46, 173.65. Anal. Calcd. For C23H20N2OS (372.48):
C, 74.16; H, 5.41; N, 7.52. Found: C, 74.03; H, 5.44; N, 7.50.
3,4-Dihydro-4-(3-chlorophenyl)-5,6-diphenylpyrimidin-2(1H)-
thione 4i
White powder; mp 263–265◦C; IR (KBr) νmax: 3161, 3095, 2976, 1649,
1
1573, 1481 cm−1; H NMR(DMSO) δ: 5.20 (s, 1H, CH), 6.79–7.42 (m,
14H, Ar-H), 9.32 (s, 1H, NH), 9.96 (s, 1H, NH); 13C NMR (DMSO) δ:
58.20, 110.65, 125.69, 126.44, 127.00, 127.85, 127.90, 128.04, 128.51,
128.96, 129.56, 130.71, 133.25, 133.62, 133.78, 136.86, 144.68, 173.76.
Anal. Calcd. For C22H17ClN2S (376.08): C, 70.11; H, 4.55; N, 7.43.
Found: C, 70.21; H, 4.53; N, 7.41.
3,4-Dihydro-4-(3-chlorophenyl)-5,6-dimethylpyrimidin-2(1H)-
one 4j
White powder; mp 228–230◦C; IR (KBr) νmax: 3238, 3085, 2914, 1687,
1587, 1489 cm−1 1H NMR(DMSO) δ: 1.79 (s, 3H, Me), 2.12 (s, 3H,
;
Me), 4.79 (s, 1H, CH), 7.34–7.45 (m, 4H, Ar-H), 7.63 (s, 1H, NH), 8.13
(s, 1H, NH); 13C NMR (DMSO) δ: 14.40, 19.04, 59.58, 109.75, 120.20,
127.44, 128.53, 130.48, 133.50, 139.13, 146.31, 152.84. Anal. Calcd. For
C12H13ClN2O (236.70): C, 60.89; H, 5.54; N, 11.84. Found: C, 61.01; H,
5.51; N, 11.86.

1804
H. Kefayati et al.
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