Studies on the synthesis of 2‐(2‐arylvinyl)thieno[2,3‐d]pyrimidines and 5‐(2‐arylvinyl)triazolothieno[3,2‐e]pyrimidines

Synthesis of 2‐(2‐arylvinyl)thienopyrimidines, by the acid catalyzed condensation of nitriles with thiophene o‐aminocarbonyl compounds, the condensation of aldehydes with thiophene o‐aminoamides, the base catalyzed condensation of aldehydes with 2‐methylthienopyrimidines and by the Wittig condensation of 2‐thieno‐pyrimidinylmethylphosphonium salts with aldehydes is described. Isomeric 5‐methyltriazolothienopyrimidines were found to react, under basic condition, with aldehydes yielding 5‐(2‐arylvinyl)triazolo[2,3‐c]thieno‐pyrimidines. While 5‐styryltriazolo[4,3‐c] isomers resisted acid catalysed isomerization, they were found to isomerize to triazolo[2,3‐c]pyrimidines under base catalysis.