3,4-DIHYDROPYRIMIDIN-2(1H)-ONES
1215
Table 4. Influence of xanthan sulfuric acid on reaction rates and yieldsa
Entry
Catalyst (g)
Time (min)
Yield (%)b
1
2
3
4
5
6
None
0.01
0.04
0.08
0.1
120
20
20
20
20
40
Trace
25
51
81
95
0.1
95
aReaction conditions: Mixture of benzaldehyde (1 mmol), EAA (1 mmol),
urea (1.5 mmol), and xanthan sulfuric acid (0.1 g) stirred at 40 ꢀC under
solvent-free conditions.
bIsolated yield.
Ethyl 1,2,3,4-tetrahydro-6-methyl-4-(6-nitro-4-oxo-4H-chromen-3-yl)-2-
oxopyrimidine-5-carboxylate (Table 3, Entry 4o). Mp 90 ꢀC. 1H NMR
(DMSO-d6): d 9.13 (bs, 1H, NH), 7.92 (bs, 1H, NH), 7.12–7.25 (m, 3H, Ar-H),
7.02 (s, 1H, CH), 5.18 (s, 1H, C4-H), 4.09 (q, 2H, OCH2), 2.40 (s,3H, CH3), 1.75
(t, 3H, CH3); IR (KBr): 3250, 3196, 1734, 1716, 1652 cmꢁ1. EIMS, 70 ev, m=z: 373
(Mþ). Calcd. for C17H15N3O7: C, 54.69; H, 4.05; N, 11.26. Found: C, 54.62; H,
4.16; N, 11.06.
Ethyl 1,2,3,4-tetrahydro-6-methyl-4-(naphthalen-6-yl)-2-thioxopyrimi-
1
dine-5-carboxylate (Table 3, Entry 4p). Mp 149–150 ꢀC. H NMR (DMSO-d6):
d 9.27 (bs, 1H, NH), 7.52 (bs, 1H, NH), 7.20–7.81 (m, 7H, CH), 5.19 (s, 1H, C4-
H), 3.97 (q, 2H, OCH2), 2.25 (s,3H, CH3), 1.10 (t, 3H, CH3); IR (KBr) : 3245,
3170, 1723, 1639 cmꢁ1. EIMS, 70 ev, m=z: 326 (Mþ). Calcd. for C17H15N3O7: C,
66.23; H, 5.56; N, 8.58. Found: C, 66.31; H, 5.44; N, 8.62.
Ethyl 1,2,3,4-tetrahydro-4-(7-hydroxy-2-oxo-2H-chromen-8-yl)-6-methyl-
1
2-oxopyrimidine-5-carboxylate (Table 3, Entry 4q). Mp 121–122 ꢀC. H NMR
(DMSO-d6): d 9.23 (bs, 1H, NH), 8.01 (d, 1H, C4-H), 7.90 (bs,1H, NH), 7.57 (d,
1H, Ar-H), 7.14 (d, 1H, Ar-H), 6.35 (d, 1H), 5.12 (d, 1H, C4-H), 3.97 (q, 2H,
OCH2), 2.20 (s,3H, CH3), 1.17 (t, 3H, CH3); IR (KBr): 3415, 3,315, 1728, 1710,
1690 cmꢁ1. EIMS, 70 ev, m=z: 344 (Mþ). Calcd. for C17H16N2O6: C, 59.30; H,
4.68; N, 8.14. Found: C, 59.37; H, 4.54; N, 8.09.
Ethyl
1,2,3,4-tetrahydro-6-methyl-2-oxo-4-(4-oxo-4H-chromen-3-yl)
1
pyrimidine-5-carboxylate (Table 3, Entry 4r). Mp 110 ꢀC. H NMR (DMSO-
d6): d 9.40 (bs, 1H, NH), 8.20 (d, 1H, Ar-H), 7.90 (bs, 1H, NH), 7.45-7.60 (m,
3H, Ar-H), 6.95 (1H, CH), 5.10 (s, 1H, C4-H), 4.12 (q, 2H, OCH2), 2.20 (s, 3H,
CH3), 1.25 (t, 3H, CH3); IR (KBr): 3310, 3170, 1734, 1710, 1695 cmꢁ1. EIMS,
70 ev, m=z: 328 (Mþ). Calcd. for C17H16N2O5: C, 62.19; H, 4.91; N, 8.53. Found:
C, 62.27; H, 4.83; N, 8.59.
CONCLUSION
In conclusion, we have developed a mild, simple, cost-effective procedure
for the synthesis of 3,4-dihydropyrimidinones=thiones using a reusable solid acid