One–pot synthesis of 1,2,4-triazole-Fused heterocycles via sequential condensation and iron-catalyzed aerobic oxidation

Abstract

A one-pot method has been devised for the synthesis of 1,2,4-triazole-fused heterocycles. This method involves the condensation of commercially available (hetero)aromatic/aliphatic aldehydes and 2-hydrazinopyridine derivatives, succeeded by iron-catalyzed oxidation using O2 in air as the oxidant and without using any ligands or additives. The salient merits of this chemistry include broad substrate scope, simple operation, one-pot synthesis, and excellent functional group tolerance, as well as the use of air, a cheap and abundant iron catalyst, and ligand- and additive-free conditions. The efficacy of this synthetic method has been demonstrated through the synthesis of 30 examples of 1,2,4-triazole-fused heterocycles with diverse substituents in moderate to excellent yields. Furthermore, the successful synthesis of an antibacterial agent has been achieved with a satisfactory yield.