Efficient synthesis of 3-substituted 1,2,4-triazolo[4,3-a]pyridine by [bis(trifluroacetoxy)iodo]benzene-catalyzed oxidative intramolecular cyclization of heterocyclic hydrazones

摘要

A series of 1,2,4-triazolopyridines have been prepared by oxidative intramolecular cyclization of heterocyclic hydrazones with [bis(trifluroacetoxy) iodo]benzene. General applicability of this simple transformation was confirmed by synthesis of 1,2,4-triazolo[4,3-a]pyridine. The advantages of this protocol are the nontoxicity of catalyst and shorter reaction time to obtain good preparative yield.