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27. Synthesis of 2-methyl-5-phenylthieno[2,3-d]pyrimidin-4(3H)-one (Vxxvii)Part-IIExperimentalA mixture of ethyl 2-amino-4-phenylthiophene-3-carboxylate (Iv, 4.9 gm; 0.02 mole),acetonitrile (1.0 gm; 0.022 mole) and catalytic amount of HCl (0.5 ml) were reactedunder microwave irradiation (45 min) as per procedure described for the compound Vi.The crude product on recrystallization from methanol-chloroform mixture yielded 2-methyl-5-phenylthieno[2,3-d]pyrimidin-4(3H)-one (Vxxvii).M.P. : 235-237 o C (235-237 o C) 10 ; Yield: 77%Mol. Formula : C 13 H 10 N 2 OS; Mol. Wt. 242.3IR (KBr) cm -1 : 2998(γ C-H ), 1667(γ CONH ).1 H NMR (CDCl 3 )δppm : 3.36 (3H, s, CH 3 ), 7.31-7.50 (5H, m, Ar-H and 1H at 6), 12.28(1H, s, NH).28. Synthesis of ethyl 3,4-dihydro-2,5-dimethyl-4-oxothieno[2,3-d]pyrimidine 6-carboxylate (Vxxviii)A mixture of diethyl 5-amino-3-methylthiophene-2,4-dicarboxylate (Iiii, 5.1 gm; 0.02mole), acetonitrile (1.0 gm; 0.022 mole) and catalytic amount of HCl (0.5 ml) werereacted under microwave irradiation (30 min) as per procedure described for thecompound Vi. The crude product on recrystallization from methanol-chloroform mixtureyielded ethyl 3,4-dihydro-2,5-dimethyl-4-oxothieno[2,3-d]pyrimidine 6-carboxylate(Vxxviii).M.P. : 278-280 o C (280-283 o C) 11 ; Yield: 99%Mol. Formula : C 11 H 12 N 2 O 3 S; Mol. Wt. 252.29IR (KBr) cm -1 : 2960(γ C-H ), 1718(γ C=O ) 1667(γ CONH ).1 H NMR (CDCl 3 )δppm : 1.40 (3H, t, CH 3 , J = 7.3), 2.55 ( 3H, s, CH 3 ), 2.94 (3H, s, CH 3 ),4.36 (2H, CH 2 quartlet, J = 7.1), 10.95 (1H, s, NH).29. Synthesis of 2-methyl-5,6,7,8-tetrahydro-3H-benzo[4,5]thieno[2,3-d]pyrimidin-4-one (Vxxix)A mixture of ethyl 2-amino-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate (Ii, 4.5gm; 0.02 mole), acetonitrile (1.0 gm; 0.022 mole) and catalytic amount of HCl (0.5 ml)were reacted under microwave irradiation (30 min) as per procedure described for the374