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 pyrimidines derivative from the same starting material, 2- amino - 4,5 -di (alkyl) thiophene-3- carboxamide, has been 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 air oxidation. The products were obtained in high yield with an easy work-up in simple reaction along with the purification of products by non-chromatographic method. This general synthetic procedure can be extended to the preparation of a wide variety of isomeric triazoles using 2-amino thiophene-3-carboxamide bifunctional derivatives.