Mononuclear heterocyclic rearrangements. Part 11. Kinetic study of the rearrangement of (Z)-phenylhydrazones of some 5-alkyl-3-benzoyl-1,2,4-oxadiazoles into 4-acylamino-2,5-diphenyl-1,2,3-triazoles in benzene, dioxane–water, and acetonitrile

Abstract

The kinetics of the title reactions have been measured at various catalyst concentrations. The 5-alkyl-substituted phenylhydrazones (alkyl = Me, Et, Prⁱ, or Bu^t) rearrange more slowly than the 5-H parent compound; moreover the rearrangement rate is little affected by the structure of the 5-alkyl substituent. These facts are considered as evidence against a rearrangement mechanism involving catalyst addition to the C(5)–N(4) bond of the 1,2,4-oxadiazole ring. The observed reactivity pattern can be related to the influence of the 5-substituent on the leaving group ability of the substituent–C(5)–O system.