Two approaches to a new heterocyclic system of pyrazolo[4,3-e][1,2,4] triazolo[1,5-c]pyrimidine

Derivatives of a new heterocyclic system, viz. pyrazolo[4,3-e][1,2,4] triazolo[1,5-c] pyrimidine 5, have been synthesized by coupling imidoesters of 1-substituted-5-aminocarbonitriles 2 with acylhydrazides. The thermal recyclization of 1-substituted-4-(2-acylhydrazin-1-yl) pyrazolo[3,4d]-pyrimidines 7 is found to be an alternative approach to the heterocyclic system 5.