H2SO4/Silica gel: An Efficient and Reusable Heterogeneous Catalyst for the Synthesis of Pyrazolo[4,3-e][1,2,4]triazolo[4,3-c]pyrimidines

Abstract

Sulfuric acid adsorbed on silica gel has been used as an effective and reusable catalyst for the synthesis of pyrazolo[4,3-e][1,2,4]triazolo-[4,3-c]pyrimidines through cyclocondensation of 4- hydrazino-1H-pyrazolo[3,4-d]pyrimidines with triethylorthoesters under conventional heating and solvent-free microwave irradiation conditions. The present methodology offers several advantages, such as high yields, short reaction times, mild reaction condition and a recyclable and relatively green catalyst with easy work up.