AN EFFICIENT IMINOPHOSPHORANE-MEDIATED SYNTHESIS FOR PYRIDO[3',2'4,5]THIENO[3,2-D] PYRIMIDINE-DERIVATIVES

A ready one-pat preparation for pyridothienopyrimidines bearing variou s substituents at position 2 of the pyrimidine ring is reported. The a za Wittig-type reaction of iminophosphoranes derived from the aldehyde 4 with heterocumulenes leads to functionalized fused pyrimidines. Imi nophosphoranes 6, nylphosphoranylidine)amino]thieno[2,3-b]pyridines, r eact with isocyanates, carbon dioxide and carbon disulfide under mild conditions to give the functionalized 3-dihydropyrido[3',2':4,5]thieno [3,2-d]pyrimidines 7, 8 and 9, respectively.