9
8
Transition Met Chem (2013) 38:93–103
Table 4 continued
Entry
Product
Yield (%)
88
MP (°C) (observed)
MP (°C) (reported) [Ref.]
6
217–220
216–218 [23]
O
O
Cl
O
EtO
NH
N
H
7
60
195–197
196–197 [18]
EtO
NH
N
H
O
4-(4-Chloro-phenyl)-6-methyl-2-oxo-1,2,3,4-tetrahydro-
pyrimidine-5-carboxylic acid ethyl ester (Table 2, entry 2)
the microwave oven for shaking. The total period of
microwave irradiation was 5 min. The progress of the
reaction was monitored by TLC. After completion of
reaction, the resulting mixture was dissolved in 10 ml
ethanol and poured into 50 ml water. The resulting pre-
cipitate was filtered off and purified by silica gel column
chromatography using chloroform as eluent, to afford the
desired 1,4-dihydropyridine in pure form.
White powder, IR (KBr): 1,651, 1,711, 2,957, 3,106,
1
-
1
3
,230 cm
.
H
NMR (DMSO-d6): d = 1.10 (t,
J = 7.1 Hz, 3H, CH ), 2.26 (s, 3H, CH ), 3.99 (q,
3
3
J = 7.1 Hz, 2H, CH ), 5.14 (d, J = 3.3 Hz, 1H, CH), 7.25
2
(
d, J = 8.4 Hz, 2H, arom CH), 7.40 (d, 8.4 Hz, 2H, arom
1
3
CH), 7.77 (s, 1H, NH), 9.24 (s, 1H, NH). C NMR
(
DMSO-d ) d = 14.9, 18.6, 54.2, 60.1, 99.6, 129.0, 129.2,
32.6, 144.6, 149.6, 152.7, 166.0.
6
Spectral data of selected compounds
1
Diethyl 1,4-dihydro-2,6-dimethyl-4-phenylpyridine-3,5-
dicarboxylate (Table 3, entry 1)
6-Methyl-4-(4-nitro-phenyl)-2-oxo-1,2,3,4-tetrahydro-
pyrimidine-5-carboxylic acid ethyl ester (Table 2, entry 3)
Yellow powder, IR (KBr): 1,703, 2,950, 3,100,
1 1
Pale yellow powder, IR (KBr): 1,343, 1,520, 1,641, 1,702,
-
-
3
,300 cm . H NMR (CDCl , 500 MHz): d (ppm) 1.24
1
1
3
2
,957, 3,007, 3,106, 3,230 cm . H NMR (DMSO-d ):
6
(6H, t, J = 7.0 Hz, 2CH ), 3.37 (6H, s, CH ), 4.13 (4H, m,
3 3
d = 1.10 (t, J = 7.0 Hz, 3H, CH ), 2.28 (s, 3H, CH ), 3.99
3
3
2
7
CH ), 5.02 (1H, s, CH aliphatic), 5.72 (1H, s, NH),
2
(
q, J = 7.0 Hz, 2H, CH ), 5.28 (d, J = 2.7 Hz, 1H, CH),
2
13
.12–7.35 (5H, m, arom). CNMR (CDCl , 125 MHz): d
3
7
.51 (t, J = 8.5 Hz, 1H, arom CH), 7.91 (s, 1H, NH), 8.22
(ppm) 14.5, 20.4, 40.2, 60.6, 104.5, 126.8, 128.3, 128.8,
1
d, J = 8.5 Hz, 1H, arom CH), 9.36 (s, 1H, NH). C NMR
3
(
145.0, 148.3, 168.5.
(
DMSO-d ) d = 14.9, 18.7, 54.5, 60.2, 99.0, 124.6, 128.5,
6
1
47.5, 150.2, 152.6, 152.8, 165.9.
Diethyl 1,4-dihydro-2,6-dimethyl-4-(3-nitrophenyl)
pyridine-3,5-dicarboxylate (Table 3, entry 4)
General procedure for the synthesis
of 1,4-dihydropyridines
Yellow powder, IR (KBr): 1,695, 2,970, 3,080,
-
1 1
3,320 cm . H NMR (CDCl , 500 MHz): d (ppm) 1.28
A mixture of aldehyde (1 mmol), ethylacetoacetate
3
(
2 mmol), NH OAc (1 mmol), and [Fe(III)(salen)]Cl
4
(6H, t, J = 7.0 Hz, 2CH ), 2.40 (6H, s, 2CH ), 4.15 (4H,
3
3
(
5 mmol %) in glycerol (4 ml) was placed in a microwave
m, 2OCH ), 5.12 (1H, s, CH), 5.85 (1H, s, NH), 7.44 (1H, t,
2
oven and irradiated for a period of 1 min at a time. After
each irradiation, the reaction mixture was removed from
J = 7.5 Hz, CH arom), 7.66 (1H, d, J = 7.5 Hz, CH
arom), 8.03 (1H, d, J = 7.6 Hz, CH arom), 8.16 (1H, s, CH
1
23