12004
P. Singh et al. / Tetrahedron 61 (2005) 11999–12005
3.4. General procedure for Diels–Alder cycloaddition
between 3c and dienophiles
(75 MHz, CDCl ): 14.1 (–O–C–CH ), 24.4 [–C (H-6)], 34.1
3 3
[–C (H-7)], 39.5 [–C (H-8)], 42.2 [–C (H-3)], 62.7 (–OCH2),
22.6, 125.8, 127.8, 128.4, 130.2, 135.2, 158.2, 158.9,
C
160.4, 175.3 and 177.2. m/z: 374 (M ).
1
Bicyclic pyrimidinone 3c (5.0 mmol) and dienophiles
[
(
(
N-phenylmaleimide (5.0 mmol), N-tolylmaleimide
5.0 mmol), maleic anhydride (5.0 mmol), methylacrylate
5.2 mmol) and acrylonitrile (5.2 mmol)] were refluxed in
3
.4.4. 6-(6-Methoxycarbonyl-cyclohex-2-enyl)-5-oxo-5H-
thiazolo[3,2-a]pyrimidine-2-carboxylic acid ethyl ester
ortho)/6-(5-methoxycarbonyl-cyclohex-2-enyl)-5-oxo-
H-thiazolo[3,2-a]pyrimidine-2-carboxylic acid ethyl
dry toluene for 16–18 h. The solvent was removed under
reduced pressure and the crude product thus obtained was
purified by recrystallisation from a mixture (1:5, v/v) of
ethylacetate and hexane.
(
5
ester (meta)(5a). Colourless crystalline solid, yield: 68%;
mp 103–104 8C. Anal. Calcd for C H N O S: C, 56.34; H,
1
7 18 2 5
5
nmax: 1724, 1683, 1508 cm . d (300 MHz, CDCl ): 1.40
.01; N, 7.73. Found: C, 56.61; H, 4.95; N, 7.69%. IR (KBr)
3
1
.4.1. 6-(1,3-Dioxo-2-phenyl-2,3,3a,4,7,7a-hexahydro-
H-isoindol-4-yl)-5-oxo-5H-thiazolo[3,2-a]pyrimidine-2-
K1
H
3
[
t, 6H, JZ7.2 Hz, 2!–O–C–CH (o and m)], 1.72–1.80 [m,
carboxylic acid ethyl ester (4a). Light yellow solid, yield:
8
3
2
H, H , H (o)], 1.91–1.93 [m, 2H, H , H (m)], 2.14–
7a 7b 7a 7b
2%; mp 207–208 8C. Anal. Calcd for C H N O S: C,
2
3 19 3 5
2
.20 [m, 2H, H , H (o)], 2.22–2.24 [m, 2H, H , H (m)],
6a 6b 6a 6b
61.46; H, 4.26; N, 9.35. Found: C, 61.86; H, 4.61; N, 9.32%.
IR (KBr) nmax: 1708, 1666, 1510, 1386 cm . dH
K1
2
.89–2.91 [m, 1H, H (m)], 3.01 [unresolved dd, JZ5.4,
8
7
–
.5 Hz, 1H, H (o)], 3.58 [s, 3H, –OCH (o)], 3.64 [s, 3H,
OCH (m)], 3.95 [ddd, JZ3.1, 5.4, 10.5 Hz, 1H, H (m)],
3 3
(
300 MHz, CDCl ): 1.42 (t, 3H, JZ7.2 Hz, –O–C–CH ),
8
3
3
3
2
.40 (unresolved ddd, JZ7.5, 15.3 Hz, 1H, H ), 2.99
6
a
4
.13 [dd, JZ3.2, 9.2 Hz, 1H, H (o)], 4.41 [q, JZ7.2 Hz,
(
unresolved ddd, JZ4.5, 15.3 Hz, 1H, H ), 3.44 (ddd, JZ
3
6
b
4
H, 2!–CH (o and m)], 5.61–5.63 [m, 1H, H (m)], 5.64–
2 4
1
3
7
7
.8, 7.2, 9.3 Hz, 1H, H ), 3.79 (dd, JZ6.9, 9.1 Hz, 1H, H ),
7
8
5
[m, 1H, H
.66 [m, 1H, H (o)], 5.98–6.00 [m, 1H, H (m)], 6.01–6.03
4
.97 (unresolved dd, JZ6.6 Hz, 1H. H ), 4.42 (q, JZ
5
3
.2 Hz, 2H, –OCH ), 6.21–6.23 (m, 2H, H and H ), 7.15–
.43 (m, 5H, ArH), 7.99 (s, 1H, H ), 8.58 (s, 1H, H ). d
C
5
(o)], 7.88 [s, 1H, H
1
(o)], 7.91 [s, 1H, H (m)],
1
2
4
5
8.51 [s, 1H, H
CDCl ): 14.2 [–O–C–CH
3
(o)], 8.53 [s, 1H, H
(m)]. d (75 MHz,
2 C
1
2
2
(
75 MHz, CDCl ): 14.1 (–CH ), 24.3 [C (H-6)], 33.4 [–C
3
3
(o and m)], 21.5 [–C (H-7) (m)],
3
(
1
1
H-7)], 39.8 [–C (H-8)], 42.0 [–C (H-3)], 62.7 (–OCH2),
22.5 [–C (H-7) (o)], 22.6 [–C (H-6) (o)], 24.2 [–C (H-6)
(m)], 29.1 [–C (H-8) (o)], 30.1 [–C (H-8) (m)], 34.3 [–C
20.7, 126.2, 126.7, 128.0, 128.2, 128.4, 128.9, 129.4,
31.6, 151.7, 158.3, 159.7, 161.1, 176.2 and 178.3. m/z: 449
(H-3) (m)], 37.2 [–C (H-3)], 52.8 [–OCH
(m)], 62.7 [–OCH (o and m)], 117.4 (o), 118.0 (m), 120.9
o), 121.0 (m), 123.3 (o), 123.5 (m), 127.3 (o), 127.4 (m),
(o)], 53.4 [–OCH
3 3
C
(
M ).
2
(
3
1
.4.2. 6-(1,3-Dioxo-2-p-tolyl-2,3,3a,4,7,7a-hexahydro-
H-isoindol-4-yl)-5-oxo-5H-thiazolo[3,2-a]pyrimidine-2-
129.5 (o), 130.2 (m), 152.1 (o), 152.3 (m), 153.6 (o), 153.7
(m), 159.5 (o), 160.1 (m), 162.2 (o), 162.3 (m), 163.6 (o) and
163.7 (m). m/z: 362 (M ).
C
carboxylic acid ethyl ester (4b). Pale white solid, yield:
8
6
1%; mp 213–215 8C. Anal. Calcd for C H N O S: C,
24 21 3 5
2.19; H, 4.57; N, 9.07. Found: C, 62.49; H, 4.22; N, 8.99%.
K1
3.4.5. 6-(6-Cyano-cyclohex-2-enyl)-5-oxo-5H-thiazolo[3,
2
IR (KBr) nmax: 1712, 1669, 1512 cm . dH (300 MHz,
CDCl ): 1.41 (t, 3H, JZ7.2 Hz, –O–C–CH ), 2.39 (s, 3H,
-a]pyrimidine-2-carboxylic acid ethyl ester (ortho)/6-(5-
3
3
cyano-cyclohex-2-enyl)-5-oxo-5H-thiazolo[3,2-a]pyrimi-
dine-2-carboxylic acid ethyl ester (meta)(5b). Light
yellow crystalline solid, yield: 75%; mp 107–108 8C.
Anal. Calcd for C H N O S: C, 58.34; H, 4.59; N,
–
CH ) 2.42 (unresolved ddd, JZ7.5, 15.2 Hz, 1H, H ),
3
6
a
3
.01 (unresolved ddd, JZ4.2, 15.2 Hz, 1H, H ), 3.43 (ddd,
6
b
JZ1.8, 7.5, 9.5 Hz, 1H, H ), 3.81 (dd, JZ6.6, 9.2 Hz, 1H,
H ), 3.96 (unresolved dd, JZ6.8 Hz, 1H. H ), 4.41 (q, JZ
7
7.01 (d, JZ8.0 Hz, 2H, ArH), 7.02–7.04 (d, JZ8.0 Hz, 2H,
ArH), 7.98 (s, 1H, H ), 8.59 (s, 1H, H ). d (75 MHz,
CDCl ): 14.1 (–O–C–CH ), 20.9 (–CH ) 24.3 [–C (H-6)],
3
7
1
6 15 3 3
8
3
1
1
2.76. Found: C, 58.51; H, 4.41; N, 12.69%. IR (KBr) nmax:
718, 1676, 1508 cm . d (300 MHz, CDCl ): 1.41 [t, 6H,
.2 Hz, 2H, –OCH ), 6.20–6.23 (m, 2H, H and H ), 6.98–
2 4 5
K1
H
3
JZ7.2 Hz, 2!–O–C–CH (o and m)], 1.71–1.82 [m, 2H,
3
1
2
C
H , H (o)], 1.88–1.92 [m, 2H, H , H (m)], 2.15–2.19
[m, 2H, H , H (o)], 2.21–2.24 [m, 2H, H , H (m)],
7a
7b
7a
7b
3
3
3
(
3.3 [–C(H-7)], 39.9 [–C(H-8)], 42.1 [–C(H-3)], 62.8
–OCH ), 120.6, 125.8, 126.4, 127.8, 128.4, 129.1, 130.2,
6a 6b 6a 6b
2
7
.89–2.91 [m, 1H, H (m)], 3.03 [unresolved dd, JZ5.4,
8
2
.4 Hz, 1H, H (o)], 3.89 [ddd, JZ3.2, 5.4, 10.5 Hz, 1H, H
131.4, 135.2, 152.6, 158.2, 159.6, 161.2, 176.3 and 178.2.
m/z: 463 (M ).
8
3
C
(
m)], 4.11 [dd, JZ3.2, 9.6 Hz, 1H, H (o)], 4.43 [q, JZ
3
7
5
6
.2 Hz, 4H, 2!–CH (o and m)], 5.59–5.62 [m, 1H, H (m)],
.63–5.68 [m, 1H, H (o)], 5.88–5.99 [m, 1H, H (m)],
2
4
3
.4.3. 6-(1,3-Dioxo-1,3,3a,4,7,7a-hexahydro-isobenzo-
4
5
.03–6.08 [m, 1H, H (o)], 7.84 [s, 1H, H (o)], 7.89 [s, 1H,
5
furan-4-yl)-5-oxo-5H-thiazolo[3,2-a]pyrimidine-2-car-
boxylc acid ethyl ester (4c). Colorless solid, yield: 72%;
mp 219–221 8C. Anal. Calcd for C H N O S: C, 54.54; H,
1
H (m)], 8.52 [s, 1H, H (o)], 8.53 [s, 1H, H (m)]. d
C
1
2
2
(
(
75 MHz CDCl ): 14.1 [–O–C–CH (o and m)], 21.6 [–C
3 3
H-7) (m)], 22.5 [–C (H-7) (o)], 22.7 [–C (H-6) (o)], 24.2
1
7 14 2 6
3.77; N, 7.48. Found: C, 54.68; H, 3.67; N, 7.34%. IR (KBr)
nmax: 1710, 1665, 1514 cm . d (300 MHz, CDCl ): 1.42
K1
[–C (H-6) (m)], 28.8 [–C (H-8) (o)], 30.2 [–C (H-8) (m)],
34.4 [–C (H-3) (m)], 37.2 [–C (H-3)], 62.9 [–OCH (o and
H
3
(
t, 3H, JZ7.2 Hz, –O–C–CH ), 2.40 (unresolved ddd, JZ
2
3
7
1
3
6
.4, 15.1 Hz, 1H, H ), 2.99 (unresolved ddd, JZ4.3,
m)], 118.7 (o), 118.8 (m), 121.0 (o), 121.2 (m), 124.4 (o),
124.7 (m), 126.7 (o), 126.8 (m), 129.5 (o), 130.1 (m), 152.0
(o), 152.1 (m), 152.9 (o), 153.0 (m), 157.5 (o), 157.6 (m),
159.6 (o), 159.7 (m), 162.1 (o) and 162.3 (m). m/z: 329
6
a
5.2 Hz, 1H, H ), 3.44 (ddd, JZ1.7, 7.2, 9.5 Hz, 1H, H ),
6
b
7
.82 (dd, JZ6.5, 9.5 Hz, 1H, H ), 3.97 (unresolved dd, JZ
8
.6 Hz, 1H. H ), 4.41 (q, JZ7.2 Hz, 2H, –OCH ), 6.19–6.23
3
2
C
(
m, 2H, H and H ), 7.99 (s, 1H, H ), 8.61 (s, 1H, H ). d
C
(M ).
4
5
1
2