A New Synthesis of Pyrazolo- [4,3-e][1,2,4]triazines via Acid Promoted Ring Closure of the Phenylhydrazones of 5-Acyl-1,2,4-triazines

Abstract

The reaction of various substituted phenylhydrazones of 5-acyl-1,2,4triazines in the presence of 1.1 equivalent of HCl in boiling ethanol-dioxane mixture has been studied.In all reactions the formation of the corresponding pyrazolo[4,3-e][1,2,4]triazines (3a-r) takes place in good yield.The structures of 3a-r were unequivocally established by spectroscopic methods as well as by X-Ray analysis of selected 5-methyl-3-phenyl-7-(p-tolyl)pyrazolo [4,3-e][1,2,4]triazine (3a).