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Part-IExperimentalNMR (CDCl 3 )δppm : 1.62 (4H, s, CH 2 at 6 & 7), 2.77 (2H, s, CH 2 at 4), 3.02 (2H, s,MS m/e : 255(M + ), 221, 149.CH 2 at 8), 4.55 (2H, s, CH 2 at 2), 10.60 (1H, s, NH at 3).2. Reaction of 2-amino-3-carbethoxy-5-carbemethoxy-4-methylthiophene withchloroacetonitrile in the presence of dry hydrogen chloride gas (IIii)A stream of dry hydrogen chloride gas was bubbled through an ice-cold mixture of 2-amino-3-carbethoxy-5-carbemethoxy-4-methylthiophene (Iii, 16.3 gm; 0.06 mole) andchloroacetonitrile (6.8 gm; 0.09 mole) in dry dioxane (60 ml) for 6-8 hrs. The reactionwas worked up as for IIi. The crude product on recrystallisation from dioxane yieldedfine needles (14 gm; 86%), melting at 250-250 o C, characterized as methyl 2-(chloromethyl)-3,4-dihydro-5-methyl-4-oxothieno[2,3-d]pyrimidine 6-carboxylate (IIii).Mol. Formula : C 10 H 9 ClN 2 O 3 S; Mol. Wt. 272.71IR (KBr) cm -1 : 1724(γ COO- ), 1664(γ CONH ), 2863(γ ArH ), 1254(γ CH2 ), 686(γ C-Cl ).3. Reaction of diethyl 5-amino-3-methylthiophene 2,4-dicarboxylate with chloroacetonitrilein the presence of dry hydrogen chloride gas (IIiii)A stream of dry hydrogen chloride gas was bubbled through an ice-cold mixture ofdiethyl 5-amino-3-methylthiophene 2,4-dicarboxylate (Iiii, 17.1 gm; 0.06 mole) andchloroacetonitrile (6.8 gm; 0.09 mole) in dry dioxane (60 ml) for 6-8 hrs. The reactionwas woked up as for IIi. The crude product on recrystallisation from dioxane yielded fineneedles (15 gm; 87%), m.p 241-243 o C (243-246 o C) 3 , characterized as ethyl 2-(chloromethyl)-3,4-dihydro-5-methyl-4-oxothieno[2,3-d]pyrimidine-6-carboxylate (IIiii).Mol. Formula : C 11 H 11 ClN 2 O 3 S; Mol. Wt. 286.7IR (KBr)/cm -1 : 2864(γ CH- ), 1725(γ COO- ), 1670(γ CONH ), 763(γ C-Cl ).NMR (CDCl 3 )δppm : 1.41 (3H, t, J = 7, CH 3 ), 2.95 (3H, s, CH 3 ), 4.38 (2H, quartlet, J =7, CH 2 ), 4.57 (2H, s, CH 2 ), 10.62 (1H, s, NH),MS m/e : 286(M + ).178