Construction of 1,2,4-Triazole Derivatives via Cyclocondensation of Alkylidene Dihydropyridines and Aryldiazonium Salts

Alkylidene dihydropyridines (anhydrobases) prepared via dearomatization of N-acylated 4-(aminomethyl)pyridines participate in [3 + 2] cyclocondensation reactions with aryldiazonium cations to afford substituted 1,2,4-triazolium salts or neutral 1,2,4-triazoles in high isolated yield. The reaction proceeds in the presence of a variety of N-acyl groups and aryl-susbtituted diazonium salts and offers a general route to pyridyl-substituted 1,2,4-triazoles.