A new facile route to synthesize thieno[3,2-e][1,2,4]triazolo[4,3- c]pyrimidine derivatives

A new facile route for synthesis of 3-(aryl)-8,9-di(alkyl)thieno[3,2-e][1,2,4]triazolo pyrimidinesderivative from the same starting material, 2-amino-4,5-di(alkyl)thiophene-3-carboxamide, hasbeen developed through heterocyclization of the corresponding arylidene-hydrazino-5,6-di(alkyl)thieno[2,3-d]pyrimidine under refluxing condition with acetic anhydride followed by airoxidation. The products were obtained in high yield with an easy work-up in simple reactionalong with the purification of products by non-chromatographic method. This general syntheticprocedure can be extended to the preparation of a wide variety of isomeric triazoles using 2-aminothiophene-3-carboxamide bifunctional derivatives.

Keywords:

Thieno[3 , 2-e][1 , 2 , 4]triazolo[4 , 3-c]pyrimidines , heterocyclization , acetic anhydride , air oxidation