Transition Metal, Azide, and Oxidant-Free Homo- and Heterocoupling of Ambiphilic Tosylhydrazones to the Regioselective Triazoles and Pyrazoles

With N-tosylhydrazone as an ambiphilic reagent,
an unprecedented cyclization reaction of two identical or different
tosylhydrazones has been developed to access various 4,5-disubstituted-2H-triazoles under transition metal, azide, and oxidant-free
conditions. A mechanistic rationalization study led to the identification
of several electronically diverse unsaturated systems for regioselective
synthesis of 1- and 2-substituted 1,2,3-triazoles and pyrazoles.