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 Eksperiments

The mechanism for the thermal rearrangement of 4-alkyl-1,2,4-triazoles to the corresponding 1-alkyl-1,2,4-triazoles, was studied by cross-over experiments with mixtures of 4-ethyl-3,5-diphenyl-4H-1,2,4-t riazole and 3,5-bis(4-methylphenyl)-4-propyl-4H-1,2,4-triazole. This gave support to a proposed mechanism involving the formation of an ionic triazolium triazolate intermediate, and a subsequent nucleophilic attack of the tr iazolate anion at the 1- and 4-alkylgroup positions to form the observed products. Further support was obtained by thermolysis of a mixture of 1-ethyl-3,5-bis(4-methylphenyl)-4-propyl-1,2,4-triazolium tetrafluoroborate and potassium 3,5-diphenyl-1H-triazolate.