Facile Synthesis of Fully Substituted 1,2,4-Triazoles via [3+2] Cycloaddition of Nitrileimines with Amidine under Transition Metal-Free Conditions

An efficient synthesis of densely 1,2,4-triazoles has been achieved by [3+2] cycloaddition of nitrileimides with amidine hydrochlorides under transition metal-free conditions. This method features mild reaction conditions, wide substrate scope and good functional group tolerance. A series of aryl, heterocyclic and alkyl substituted 3-CF3-1,2,4-triazoles were synthesized smoothly under the promotion of NaHCO3 and yield up to 96%. In addition, both gram-scale reaction and synthetic transformations are smoothly elaborated to indicate the utility of this reaction.