N-cyanochloroacetamidine - A convenient reagent for the regioselective synthesis of fused diaminopyrimidines.

N-Cyanochloroacetamidin reacts wit conjugated thiolato(selenolato)nitriles to give product of regioselective S(Se) allcylation that can subsequently be involved in the Thorpe reaction. Resulting enaminocyanamidines form pyrimidine rings under acid or base catalysis forming fused diaminopyrimidines. According to this common scheme, functionally substituted thieno[3,2-d]pyrimidines, thiazolo[4,5-d]pyrimidines, pyrimido[4 '',5 '' :4',5']thieno[3',2':4,5]thieno[3',2-'d]pyrimidine, pyrido[3',2':4,5]thieno(selenopheno)[3,2-d]pyrimidines, their hydrogenated analogues,and pyrimido-[4',5':4,5]thieno[2,3 -d]pyrimidine were synthesized.