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Part-IIExperimentalM.P. : 260-262 o C; Yield: 63%Mol. Formula : C 12 H 9 Cl N 2 O 2 S; Mol Wt. 280.7IR(KBr)cm -1 : 2978(γ C-H ), 1676(γ CONH ), 736(γ C-Cl )5.5 Synthesis of condensed 2-methylpyrimidin-4(3H)-ones under MicrowaveIrradiation (MWI) (Vxxv-xxx)25. Synthesis of 2-methyl-5-(4-methylphenyl)thieno[2,3-d]pyrimidin-4(3H)-one(Vxxv)A mixture of ethyl 2-amino-4-(4-methylphenyl)thiophene-3-carboxylate (Ivii, 5.22 gm;0.02 mole), acetonitrile (1.0 gm; 0.022 mole) and catalytic amount of HCl (0.5 ml) werereacted under microwave irradiation (40 min) as per procedure described for thecompound Vi. The crude product on recrystallization from methanol-chloroform mixtureyielded 2-methyl-5-(4-methylphenyl)thieno[2,3-d]pyrimidin-4(3H)-one (Vxxv).M.P. : 97-99 o C; Yield: 80%Mol. Formula : C 14 H 12 N 2 OS; Mol. Wt. 256.3IR (KBr) cm -1 : 2898(γ C-H ), 1667(γ CONH ).1 H NMR (CDCl 3 )δppm : 2.39 (3H, s, CH 3 ), 2.47 (3H, s, CH 3 ), 7.04 (1H, s, H), 7.16-7.48(4H, m, Ar-H), 11.90 (1H, s, NH).26. Synthesis of 2,5,6-trimethylthieno[2,3-d]pyrimidin-4(3H)-one (Vxxvi)A mixture of ethyl 2-amino-4,5-dimethylthiophene 3-carboxylate (Iiv, 3.98 gm; 0.02mole), acetonitrile (1.0 gm; 0.022 mole) and catalytic amount of HCl (0.5 ml) werereacted under microwave irradiation (55 min) as per procedure described for thecompound Vi. The crude product on recrystallization from methanol-chloroform mixtureyielded 2,5,6-trimethylthieno[2,3-d]pyrimidin-4(3H)-one (Vxxvi).M.P. : 102-104 o C (102-104 o C) 10 ; Yield: 70%Mol. Formula : C 9 H 10 N 2 OS; Mol. Wt. 194.25IR (KBr) cm -1 : 2918(γ C-H ), 1665(γ CONH ).1 H NMR (CDCl 3 )δppm : 2.37 (3H, s, CH 3 ), 2.46 (3H, s, CH 3 ), 2.51 (3H, s, CH 3 ), 12.04(br, s, 1H, NH).373