Synthesis of 3-substituted pyrido[4′,3′:4,5]-thieno[2,3-d]pyrimidines and related fused thiazolo derivatives

Convenient syntheses of 3-substituted ethyl 4-oxo-2-thioxo-1,2,3,4,5,6,7,8-octahydropyrido[4' 3':4,5]thieno[2,3-d]pyrimidine-7-carboxylates 3a, b, 6, 11-13, ethyl 3-methyl-5-oxo-2,3,6,9-tetrahydro-5H-pyrido[4',3:4,5]thieno[2,3-d][1,3]thiazolo[3,2-a]-pyrimidine-8(7H)-carboxylate (4), and ethyl 2-methyl-5-oxo-2,3,6,9-tetrahydro-5H-pyrido[4', 3.-4,5]thieno[2, 3-d][1,3]thiazolo[3,2-a]pyrimidine-8[7H]carboxylate (8) from diethyl 2-isothiocyanato-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3,6-dicarboxylate (1) are reported. (C) 2003 Wiley Periodicals, Inc.