v-Triazolines. Part III. cis-trans Equilibrium of 1-aryl-4,5-dihydro-v-triazoles

Abstract

The stereochemical features of the reaction between 4-nitrophenyl azide and some enamines deriving from straight-chain aliphatic ketones or aryl alkyl ketones have been studied. Under kinetically controlled conditions the cis–trans equilibrium mixture of the enamine reacts with the azide, yielding exclusively the trans-triazoline. At higher temperature or in the presence of acidic catalysts, the trans-triazoline epimerizes, thus affording a cis–trans equilibrium mixture. The factors which affect the equilibrium position and the epimerization rate are discussed and a probable epimerization mechanism is suggested.