Dowex 50W in aqueous medium: Highly efficient biginelli condensation procedure for the synthesis of 4-aryl-3,4-dihydropyrimidones

Article abstract of DOI:10.3987/COM-06-10924

We report here Dowex 50W-mediated efficient synthesis of 4-aryl 3,4-dihydropyrimidones in water for the first time in a one-pot operation.

Full text of DOI:10.3987/COM-06-10924

HETEROCYCLES, Vol. 71, No. 1, 2007
181
HETEROCYCLES, Vol. 71, No. 1, 2007, pp. 181 - 188. © The Japan Institute of Heterocyclic Chemistry
Received, 20th October, 2006, Accepted, 17th November, 2006, Published online, 24th November, 2006. COM-06-10924
DOWEX 50W IN AQUEOUS MEDIUM: HIGHLY EFFICIENT BIGINELLI
CONDENSATION
PROCEDURE
FOR
THE
SYNTHESIS
OF
4-ARYL-3,4-DIHYDROPYRIMIDONES
a
a
b
Chhanda Mukhopadhyay, * Arup Datta, and Bimal K. Banik
a: Department of Chemistry, University of Calcutta, 92 APC Road, Kolkata-700009,
India. E.mail: csm@vsnl.net, cmukhop@hotmail.com
Fax: 91-33-23519755 , Telephone: 91-33-23371104.
b: Department of Chemistry, The University of Texas-Pan American, 1201 West
University Drive, Edinburg, Texas 78541, USA
Abstract – We report here Dowex 50W-mediated efficient synthesis of 4-aryl
3
,4-dihydropyrimidones in water for the first time in a one-pot operation.
INTRODUCTION
In recent years, 4-aryl dihydropyrimidones have shown immense interest as calcium channel blockers,
1
2
antihypertensive agents, alpha-1a-antagonists
and neuropeptide
Y
(NPY) antagonists.
3
Dihydropyrimidone-5-carboxylate moiety is also present in biologically active marine alkaloids. In this
series the most important examples are batzelladine alkaloids which are potent HIV group-120-CD4
4
inhibitors. As a result of their biological properties, synthesis of the dihydropyrimidone nucleus has
received much attention. The initial synthesis of dihydropyrimidone following Biginelli condensation
5
has proved to be inefficient with 20-50% yield. Better methods have been discovered, but through
5
b,6,7
multiple sequences and hazardous conditions.
A few other attractive methods are known, but most
1b,8
of them employ anhydrous reaction conditions and Lewis acids.
Therefore, an efficient and
operationally simple method is necessary for the synthesis of this type of multifunctionalized rings.
RESULTS AND DISCUSSION
We report here Dowex 50W-mediated synthesis of dihydropyrimidone in water for the first time in a
one-pot operation. This method has been successfully applied with a number of substrates and results in
excellent yield of the products.
The experimental procedure of our reaction is very simple. In this procedure the reactants and Dowex 50W
in water are mixed and heated (70 °C) for the specified time period (Table). After pouring in crushed ice,
an extraction of the reaction mixture with organic solvent is then followed to isolate the pure product in
excellent yield. Since Dowex 50W is a cationic ion exchange resin, maintenance of dry reaction

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HETEROCYCLES, Vol. 71, No. 1, 2007
conditions is not necessary. In addition, the additional acidic reagent is not required as Dowex 50W acts
both as a catalyst and a proton source. Very recently, dihydropyrimidones have been synthesized using
9
solvent free conditions. Our conditions employ temperature of 70 °C, yields excellent, with no side
products and very simple operational procedure. Thus Dowex 50W in water is a “green catalyst” for the
Biginelli condensation as the aqueous medium is non-hazardous and non-toxic to the environment. No
reaction takes place without the addition of Dowex 50W.
Scheme1
Ar
H
O
5
6
X
4
R
Dowex50W
water
3
NH
R
+
ArCHO +
H N
NH2
O
O
2
2
7
0°C
1
X
N
R=Me, OMe, OEt
X=O, S
H
We have investigated our reactions in water-THF (1:1), water-MeOH (1:1) or water-EtOH (1:1), but no
improvement of yield has been observed. In addition to the simplicity, our method has other benefits. For
example, this method has become successful with β-keto esters and β-diketones and a variety of substituted
aryl aldehydes. Nitro, chloro, hydroxy, methoxy, N,N-dimethylamino groups on the aryl nucleus have
remained unaffected under this reaction condition. Urea and thiourea are equally effective and produce
products with excellent yields. It has been found that 20 mg of Dowex 50W per mmol of the aldehyde is
sufficient to complete the reaction. Higher amount of Dowex 50W could not improve the yield of the
reaction. Dowex 50W can be reused three times without loss of activity. Under the same conditions,
the aliphatic aldehydes produced the dihydropyrimidones (crude by IR), but the yields being very poor,
could not be isolated in substantial amounts.
1
0
The mechanism of the dihydropyrimidone formation is similar as proposed by Folkers and Johnson. The
sulphonic acid group in Dowex 50W may stabilize the acylimine intermediate and this intermediate may
then react with the β-diketone or the β-ketoester effectively. Finally, a favorable cyclisation and
dehydration path may follow to produce the dihydropyrimidone system. Thus our method has the
following advantages:
a) the reactions are investigated in water
b) dry conditions are not needed
c) the conditions of the reactions are mild
d) additional proton sources are not required
e) Dowex 50W can be reused several times
In contrast, most the available procedures require expensive acids (catalytic or stoichiometric), dry
reaction conditions and dry solvents.

HETEROCYCLES, Vol. 71, No. 1, 2007
183
CONCLUSION
In conclusion we have demonstrated a new, mild, efficient and cost effective highly efficient procedure for
the synthesis of 4-aryl-3, 4-dihydropyrimidones in aqueous Dowex 50W. Considering the wide generality
of the substrates, this method may find useful application in synthetic organic chemistry and chemistry of
drug design.
EXPERIMENTAL
General Procedure for the Synthesis of Dihydropyrimidones: Aromatic aldehyde (4 mmoles),
β-diketone (5 mmoles) or β-ketoester (5 mmoles) and urea (6 mmoles) or thiourea (6 mmoles) were
mixed with Dowex 50W (80 mg) in water (3 mL) and heated with stirring on a water bath at 70 °C for the
specified time period (Table) till the TLC showed the absence of the starting aldehyde. The reaction
mixture was then cooled, poured onto crushed ice, stirred for 10 minutes when the solid
dihydropyrimidones separated out. It was filtered to remove Dowex 50W, dissolved in hot ethanol and
allowed to settle when the pure dihydropyrimidone crystals separated out. The products were
1
13
characterized (mp, IR, H NMR and C NMR) with respect to the known compounds (references given
in the Table).
Table. Dowex 50W catalysed synthesis of 4-aryl, 3-4 dihydropyrimidones
in aqueous medium
Entry
Ar
R
X
Time(h) Yield (%) References
1
2
Ph
Ph
Me
O
O
6
7
85
80
8, 11,13
1b, 8
OMe
3
4
5
6
7
Ph
Ph
OEt
Me
O
S
7
8
8
6
7
82
82
81
80
88
1b, 8
8
Ph
OEt
OEt
Me
S
9a
8
3-OH-C
6
H
4
O
O
4OMe-C
6
H
4
8, 13, 15
8
9
4OMe-C
4OMe-C
4OMe-C
6
6
6
H
H
H
4
4
4
OMe
OEt
OEt
OEt
O
O
S
7
8
9
7
87
85
80
78
13, 15
13, 15
13, 15
12
1
0
1
1
4NMe
2
-C
6
H
4
O

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HETEROCYCLES, Vol. 71, No. 1, 2007
1
1
2
3
4-Cl-C
6
6
H
4
4
OMe
OEt
O
O
10
10
77
75
1b, 8, 13, 15
1b, 8, 13, 15
4-Cl-C
H
14
15
16
17
3-NO
2
C
6
H
4
OEt
OMe
OMe
OEt
O
O
O
O
10
10
3
77
75
82
84
12, 14, 15
15
3-NO
2
6 4
-C H
4-OH-C
6
6
H
4
8, 16
4-OH-C
H
4
3
8 ,16
1
8
9
4-NO
2
2
-C
6
6
H
4
4
OMe
OEt
O
O
12
11
75
73
13, 15
13, 15
1
4-NO
-C
H
2
2
0
1
2-furanyl
2-furanyl
Me
O
O
6
7
75
70
8
OEt
16
2
2
4OH-3OMe-
OEt
O
6
4
81
12
6 3
C H
4
OH-3OMe-
OMe
S
82
2
3
6 3
C H
4
OH-3OMe-
OMe
O
5
75
17
2
4
C H
6
3
The physical data for majority of the compounds are given below:
1
3
5
2
–
1
1
5
-Acetyl-6-methyl-4-phenyl-3,4-dihydropyrimidin-2(1H)-one (entry 1): mp 232-235°C (lit., mp
-1 1
33-236 °C); IR (KBr): 3260, 2924, 2368, 1704, 1603, 1235 cm ; H NMR (DMSO-d
COCH ), 2.29 (s, 3H, C -CH ), 5.29 (d, J=3.4Hz, 1H, C -H), 7.22-7.36 (m, 5H, phenyl protons), 7.84 (s,
): δ 19.4, 30.8, 54.3, 110.1, 126.9, 127.8, 128.9, 144.7,
6
): δ 2.11 (s, 3H.
3
6
3
4
1
3
H, NH), 9.19 (s, 1H, NH); C NMR (DMSO-d
6
48.6, 152.6, 194.8.
-Methoxycarbonyl-6-methyl-4-phenyl-3,4-dihydropyrimidin-2(1H)-one (entry 2): mp 210-212 °C
1
b
-1 1
(
lit., mp 209-212 °C); IR (KBr): 3333, 3226, 1697, 1668, 1237, 1092 cm ; H NMR (DMSO-d
6
): δ 2.26
(
s, 3H, CH ), 3.54 (s, 3H, -OCH ), 5.15 (d, J=3.6Hz, 1H, C -H), 7.22-7.35 (m, 5H, phenyl protons), 7.75
3
3
4

HETEROCYCLES, Vol. 71, No. 1, 2007
185
1
3
(
brt, 1H, NH), 9.21 (s, 1H, NH); C NMR (DMSO-d
49.1, 152.6, 166.3.
6
): δ 18.3, 51.2, 54.3, 99.5, 126.6, 127.7, 128.9, 145,1,
1
5
2
3
1
1
5
8
-Acetyl-6-methyl-4-phenyl-3,4-dihydropyrimidin-2(1H)-thione (entry 4): mp 218-220 °C (lit., mp
-1 1
20-222 °C); IR (KBr): 3287, 1610, 1456, 1184 cm ; H NMR (DMSO-d
6
3
): δ 2.16 (s, 3H, COCH ), 2.33 (s,
H, CH ), 5.30 (d, J=3.6Hz, 1H, C -H), 7.22-7.37 (m, 5H, phenyl protons), 9.73 (d, J=3.3Hz, 1H, NH),
3
4
1
3
0.26 (s, 1H, NH); C NMR (DMSO-d ): δ 18.7, 30.8, 54.3, 111.0, 127.0, 128.2, 129.1, 143.3, 145.1,
6
74.5, 195.4.
-Ethoxycarbonyl-6-methyl-4-phenyl-3,4-dihydropyrimidin-2(1H)-thione (entry 5): mp 222-224 °C
9
a
-1 1
(
lit., mp 223-224 °C); IR (KBr): 3328, 3174, 1671, 1575, 1465, 1190, 1114 cm ; H NMR (DMSO-d
δ 1.10 ( t, J=7.2Hz, 3H, -OCH CH ), 2.30 (s, 3H, CH ), 4.01 (q, J=7.2Hz, 2H, -OCH CH
J=3.6Hz,1H, C -H), 7.21-7.37( m, 5H, phenyl protons), 9.64( s, 1H, NH), 10.32( s, 1H, NH);
6
):
2
3
3
2
3
), 5.19 (d,
1
3
4
C
NMR(DMSO-d ): δ 14.5, 17.6, 54.5, 60.1, 101.2, 126.8, 128.1, 129.0, 143.9, 145.5, 165.6, 174.7.
6
5
-Ethoxycarbonyl-4-(3-hydroxyphenyl)-6-methyl-3,4-dihydropyrimidin-2(1H)-one (entry 6): mp
8
-1 1
1
63-165 °C ( lit., mp 164-166 °C); IR (KBr): 3244, 1724, 1678, 1639, 1600, 1458, 1224, 1095 cm ; H
): δ 1.12 (t, J=7.2Hz, 3H, -OCH CH ), 2.24 (s, 3H, C -CH ), 4.00 (q, J=7.2Hz, 2H,
), 5.07 (d, J=3.3Hz, 1H, C -H), 6.61-6.69 (m, 3H, aromatic C -H, C -H and C -H), 7.09 (t,
J=8.1Hz, 1H, aromatic C -H), 7.67 (s, 1H, NH), 9.14 (s, 1H, OH), 9.36 (s, 1H, NH);
DMSO-d ): δ 14.6, 18.2, 54.3, 59.7, 99.9, 113.6, 114.6, 117.4, 129.7, 146.7, 148.5, 152.7, 157.8, 165.9.
-Acetyl-4-(4-methoxyphenyl)-6-methyl-3,4-dihydropyrimidin-2(1H)-one (entry 7): mp 178-179 °C
NMR (DMSO-d
6
2
3
6
3
-OCH CH
2
3
4
2
4
6
1
3
5
C NMR
(
6
5
1
5
-1 1
(
lit., mp177-179 °C); IR (KBr): 3249, 3108, 1717, 1625, 1237 cm ; H NMR (DMSO-d
COCH ), 2.28 (s, 3H, C -CH ), 3.72 (s, 3H, aromatic OMe), 5.21( d, J=3.3Hz, 1H, C -H), 6.88 (d, J=8.6Hz,
H, aromatic C -H and C -H), 7.17 (d, J=8.6 Hz, 2H, aromatic C -H and C -H), 7.74 (s, 1H, NH), 9.13 (s,
6
): δ 2.08 (s, 3H,
-
3
6
3
4
2
1
1
3
5
2
6
1
3
H, NH); C NMR (DMSO-d ): δ 19.3, 30.6, 53.8, 55.5, 110.1, 114.3, 128.1, 136.8, 148.2, 152.6, 159.0,
6
94.9.
5
-Ethoxycarbonyl-4-(4-methoxyphenyl)-6-methyl-3,4-dihydropyrimidin-2(1H)-one (entry 9): mp
1
5
-1
1
99-201 °C ( lit., mp 199-201 °C; IR (KBr): 3243, 3113, 2938, 1709, 1649, 1460, 1224, 1090, 781 cm ;
1
H NMR (DMSO-d
), 3.98 (q, J=7.2Hz, 2H, -OCH
C -H and C -H), 7.15 (d, J=8,7Hz, 2H, aromatic C -H and C -H), 7.65 (s, 1H, NH), 9.12 (d, J=1.2 Hz, 1H,
6
): δ 1.10 (t, J=7.2 Hz, 3H, -OCH
2
CH
3
), 2.24 (s, 3H, C
6 3
-CH ), 3.71 (s, 3H, aromatic
OCH
3
2
CH ), 5.10 (d, J=3.3 Hz, 1H, C
3
4
-H), 6.87 (d, J=8.7Hz, 2H, aromatic
3
5
2
6
1
3
NH); C NMR (DMSO-d ): δ 14.5, 18.2, 53.8, 55.5, 59.7, 100.1, 114.2, 127.9, 137.5, 148.4, 152.7, 158.9,
6
1
65.9.
5
-Ethoxycarbonyl-4-(4-methoxyphenyl)-6-methyl-3,4-dihydropyrimidin-2(1H)-thione (entry 10):
15
-1
mp 138-139 °C (lit., mp 138-140 °C); IR (KBr): 3313, 3171, 1668, 1575, 1462, 1184, 1115, 1025 cm ;

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HETEROCYCLES, Vol. 71, No. 1, 2007
1
H NMR(DMSO-d
6
): δ 1.10 (t, J=7.2Hz, 3H, -OCH
CH ), 5.12 (d, J=3.6Hz, 1H, C
-H ), 7.13 (d, J=8.4Hz, 2H, aromatic C -H and C -H), 9.57 (s, 1H, NH), 10.25 (s, 1H, NH); C
NMR (DMSO-d ): δ 14.5, 17.6, 53.9, 55.6, 60.1, 101.5. 114.3, 128.1, 136.1, 145.2, 159.2, 165.7, 174.5.
2
CH
3
), 2.28 (s, 3H, C
6 3
-CH ), 3.71 (s, 3H, aromatic
OMe), 3.99 (q, J=7.2Hz, 2H, -OCH
2
3
4
-H), 6.89 (d, J=8.4Hz, 2H, aromatic
1
3
C
3
-H and C
5
2
6
6
5
-Ethoxycarbonyl-4-(4-dimethylaminophenyl)-6-methyl-3,4-dihydropyrimidin-2(1H)-one (entry 11):
1
2
-1 1
mp 256-257 °C( lit., mp 255-257 °C); IR (KBr): 3242, 3115, 2363, 1707, 1649, 1228, 1091 cm ; H
NMR(DMSO-d ): δ 1.12 (t, J=7.2Hz, 3H, -OCH CH ), 2.23 (s, 3H, C -CH ), 2.85 [s, 6H, N(CH ], 3.98
q, J=7.2Hz, 2H, -OCH CH ), 5.04 (d, J=3.3Hz, 1H, C -H), 6.65 (d, J=8.7Hz, 2H, aromatic protons), 7.04
d, J=8.7Hz, 2H, aromatic protons), 7.57 (s, 1H, NH), 9.06 (s, 1H, NH); C NMR (DMSO-d
6
2
3
6
3
3 2
)
(
(
2
3
4
1
3
6
): δ 14.6, 18.2,
5
5
2
3.8, 59.6, 100.4, 112.7, 127.4, 133.1, 148.0, 150.2, 152.8, 166.0.
-Methoxycarbonyl-4-(4-chlorophenyl)-6-methyl-3,4-dihydropyrimidin-2(1H)-one (entry 12): mp
1
5
-1 1
03-205 °C (lit., mp 204-206 °C); IR (KBr): 3364, 3106, 2953, 1706, 1636, 1228, 1090 cm ; H NMR
): δ 2.25 (s, 3H, C -CH ), 3.53 (s, 3H, -COOMe), 5.15 (d, J=3.3Hz, 1H, C -H), 7.25 (d, J=8.4Hz,
H, aromatic protons), 7.39 (d, J=8.4Hz, 2H, aromatic protons), 7.78 (s, 1H, NH), 9.25 (s, 1H, NH); C
): δ 18.3, 51.3, 53.7, 99.2, 128.6, 128.9, 132.3, 144.0, 149.4, 152.5, 166.2.
-Ethoxycarbonyl-6-methyl-4-(3-nitrophenyl)-3,4-dihydropyrimidin-2(1H)-one (entry 14): mp
(DMSO-d
6
6
3
4
1
3
2
NMR (DMSO-d
6
5
1
5
-1 1
2
26-228 °C (lit., mp 225-227 °C); IR (KBr): 3332, 2960, 1703, 1626, 1526, 1338, 1221, 1088 cm ; H
NMR(DMSO-d ): δ 1.10(t, J=7.2Hz, 3H, -OCH CH ), 2.28 (s, 3H, C -CH ), 4.00 (q, J=7.2Hz, 2H,
6
2
3
6
3
-
OCH
2
CH
3
), 5.31 (d, J=3.3Hz, 1H, C
4
-H), 7.63-7.72 (m, 2H, aromatic C
5
-H and C
-H), 9.36 (s, 1H, NH); C NMR (DMSO-d
9.9, 98.9, 121.5, 122.8, 130.7, 133.4, 147.5, 148.2, 149.9, 152.3, 165.5.
-Ethoxycarbonyl-4-(4-hydroxyphenyl)-6-methyl-3,4-dihydropyrimidin-2(1H)-one (entry 17): mp
6
-H), 7.90 (s, 1H, NH),
1
3
8
5
5
2
.09-8.15 (m, 2H, aromatic C
2
-H and C
4
6
): δ 14.4, 18.3, 54.0,
1
6
-1 1
28-230 °C (lit., mp 227-229 °C); IR (KBr): 3512, 3119, 1687, 1645, 1463, 1232, 1090 cm ; H NMR
(
DMSO-d ): δ 1.09 (t, J=7.2Hz, 3H, -OCH CH ), 2.23 (s, 3H, C -CH ), 3.97 (q, J=7.2Hz, 2H, -OCH CH ),
6
2
3
6
3
2
3
4
5.05 (d, J=3.0 Hz, 1H, C -H), 6.69 (d, J=8.4Hz, 2H, aromatic protons), 7.03 (d, J=8.4Hz, 2H, aromatic
1
3
protons), 7.59( s,1H, NH), 9.07 (s, 1H, NH), 9.40 (brs, 1H, OH); C NMR (DMSO-d ): δ 14.5, 18.2, 53.9,
6
5
9.6, 100.3, 115.5, 127.9, 135.9, 148.2, 152.7, 157.0, 166.0.
5
-Ethoxycarbonyl-6-methyl-4-(4-nitrophenyl)-3,4-dihydropyrimidin-2(1H)-one (entry 19): mp
1
5
-1
2
05-207 °C(lit., mp 205-207 °C); IR (KBr): 3235, 3119, 2363, 1706, 1642, 1521, 1216, 1092, 779 cm ;
1
H NMR (DMSO-d
OCH CH ), 5.28 (d, J=3.3 Hz, 1H, C
NH), 8.21 (d, J=8.7Hz, 2H, aromatic C
6
): δ 1.09 (t, J=7.2Hz, 3H, -OCH
2
CH
3
), 2.26 (s, 3H, C
6
-CH
-H and C
-H), 9.32 (s, 1H, NH); C NMR (DMSO-d
6
3
), 3.98 (q, J=7.2Hz, 2H,
-H), 7.87 (s, 1H,
): δ 14.5, 18.3,
-
2
3
4
-H), 7.51 (d, J=8.7Hz, 2H, aromatic C
2
6
1
3
3
-H and C
5
5
4.1, 59.9, 98.7, 124.3, 128.1, 147.2, 149.8, 152.2, 152.4, 165.6.

HETEROCYCLES, Vol. 71, No. 1, 2007
187
5
-Ethoxycarbonyl-4-(2-furanyl)-6-methyl-3,4-dihydropyrimidin-2(1H)-one (entry 21): mp 202-204
1
6
-1 1
°
C (lit., mp 204-205 °C); IR (KBr): 3354, 3116, 2363, 1697, 1643, 1306, 1227, 1097 cm ; H NMR
DMSO-d ): δ 1.13 (t, J=6.9Hz, 3H, -OCH CH ), 2.23 (s, 3H, C -CH ), 4.03 (q, J=6.9 Hz, 2H, -OCH CH ),
.21 (d, J=3.3 Hz, 1H, C -H), 6.09 (d, J=3Hz, 1H, furanyl proton), 6.35 (t, J=2.4 Hz, 1H, furanyl proton),
.54 (t, J=1.2Hz, 1H, furanyl C
8.2, 59.7, 97.3, 105.8, 110.8, 142.6, 149.8, 152.9, 156.3, 165.5.
-Ethoxycarbonyl-4-(4-hydroxy-3-methoxyphenyl)-6-methyl-3,4-dihydropyrimidin-2(1H)-one
(
6
2
3
6
3
2
3
5
7
4
5
4
1
3
5
6
-H), 7.74 (s, 1H, NH), 9.21( s, 1H, NH); C NMR (DMSO-d ): δ 14.6, 18.2,
1
2
-1 1
(
entry 22): mp 230-232 °C (lit., mp 230-232 °C); IR (KBr): 3244, 3116, 1701, 1645, 1516, 1223 cm ; H
NMR(DMSO-d ): δ 1.12 (t, J=7.2Hz, 3H, -OCH CH ), 2.24 (s, 3H, C -CH ), 3.73 (s, 3H, aromatic OMe),
.99(q, J=7.2Hz, 2H, -OCH CH ), 5.06 (d, J=3.0 Hz, 1H, C -H), 6.62 (brd, J=8.1Hz, 1H, aromatic C -H),
.71 (dd, J=8.1Hz and 0.6 Hz, 1H, aromatic C -H), 6.80 (brs, 1H, aromatic C -H), 7.62 (s,1H, NH), 8.89 (s,
): δ 14.6, 18.2, 54.0, 56.1, 59.6, 100.1, 111.4, 115.8,
6
2
3
6
3
3
6
1
1
5
2
3
4
6
5
2
1
3
H, OH), 9.10 (s,1H, NH); C NMR (DMSO-d
6
18.8, 136.4, 146.3, 147.7, 148.3, 152.7, 165.9.
-Methoxycarbonyl-4-(4-hydroxy-3-methoxyphenyl)-6-methyl-3,4-dihydropyrimidin-2(1H)-thione
-
1 1
(
entry 23): mp 258-260 °C; IR (KBr): 3471, 3334, 3179, 1678, 1571, 1516, 1449, 1274, 1186, 752 cm ; H
NMR (DMSO-d ): δ 2.28 (s, 3H, C -CH ), 3.56 (s, 3H, -COOMe), 3.73 (s, 3H, aromatic OMe), 5.09 (d,
J=3.3 Hz, 1H, C -H), 6.60 (dd, J=8.1Hz and 1.9Hz, 1H, aromatic C -H), 6.72 (d, J=8.1Hz, 1H, aromatic
-H), 6.80 (d, J=1.9 Hz, 1H, aromatic C -H), 9.04 (s, 1H, OH), 9.55 (d, J=3.0Hz, 1H, NH), 10.25 (s, 1H,
): δ 17.6, 51.5, 54.0, 56.1, 101.2, 111.4, 115.9, 118.9, 134.8, 145.3, 146.6, 147.9,
66.2, 174.5. Anal. Calcd for C14 S: C, 54.53; H, 5.23; N, 9.08. Found: C, 54.41; H, 5.30; N, 9.11.
-Methoxycarbonyl-4-(4-hydroxy-3-methoxyphenyl)-6-methyl-3,4-dihydropyrimidin-2(1H)-one
6
6
3
4
6
C
5
2
1
3
NH); C NMR (DMSO-d
6
1
16 2 4
H N O
5
1
7
-1 1
(
entry 24): mp 251-253 °C (lit., mp 253-254 °C); IR (KBr): 3393, 3257, 1680, 1435, 1235, 1094 cm ; H
NMR(DMSO-d ): δ 2.25 (s, 3H, C -CH ), 3.54 (s, 3H, -COOMe), 3.73 (s, 3H, aromatic OMe), 5.07
6
6
3
(
J=3.3 Hz, 1H, C
4
-H), 6.60 (dd, J=8.1Hz and 1.9Hz, 1H, aromatic C
-H), 7.64 (s, 1H, NH), 8.91 (s, 1H, OH), 9.14 (s, 1H, NH); C
): δ 18.2, 51.2, 53.9, 56.1, 99.7, 111.3, 115.7, 118.6, 136.2, 146.3, 147.8, 148.7, 152.7,
6
-H), 6.71 (d, J=8.1Hz, 1H, aromatic
1
3
C
5
-H), 6.81 (d, J=1.9Hz, 1H, aromatic C
NMR(DMSO-d
66.4.
2
6
1
ACKNOWLEDGEMENT
One of the authors (A.D.) thanks the Council of Scientific and Industrial Research for his fellowship
(J.R.F.). We thank Professor Brindaban C. Ranu, Department of Chemistry, Indian Association for the
Cultivation of Science. Jadavpur, Kolkata-700032, India, for the supply of Dowex 50W and the CAS
instrumentation facility, University of Calcutta, India, for the spectral data.

188
HETEROCYCLES, Vol. 71, No. 1, 2007
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