Thermal rearrangement of 4-alkyl-4H-1,2,4-triazoles to 1-alkyl-1H-1,2,4-triazoles - A study of the mechanism by cross-over experiments

The mechanism for the thermal rearrangement of 4-alkyl-1,2,4-triazoles to t he corresponding l-alkyl-l,2,4-triazoles, was studied by cross-over experim ents with mixtures of 4-ethyl-3,5-diphenyl-4H-1,2,4-triazole and 3,5-bis(4- methylphenyl)-4-propyl-4H-1,2,4-triazole. This gave support to a proposed m echanism involving the formation of an ionic triazolium triazolate intermed iate, and a subsequent nucleophilic attack of the triazolate anion at the 1 - and 4-alkyl-group positions to form the observed products. Further suppor t was obtained by thermolysis of a mixture of 1-ethyl-3,5-bis(4-methylpheny l)-4-propyl-1,2,4-triazolium tetrafluoroborate and potassium 3,5-diphenyl-1 H-triazolate.