The Boulton–Katritzky Reaction: A Kinetic Study of the Effect of 5-Nitrogen Substituents on the Rearrangement of Some (Z)-Phenylhydrazones of 3-Benzoyl-1,2,4-oxadiazoles

The kinetics of the ring-into-ring conversion of some new
(Z)-phenylhydrazones of 3-benzoyl-1,2,4-oxadiazole containing
different nitrogen-substituents at C-5 (3b–d; X = NHMe,
NMe2, and NHCOMe) into the relevant triazoles 4b–d have
been examined in a wide range of pS+ (0.1–11.9) in 1:1
(v/v) dioxane/water solution. The obtained results have been
compared with previous data concerning the (Z)-phenyl-hydrazone of 5-amino-3-benzoyl-1,2,4-oxadiazole (3a; X =
NH2). All of the studied (Z)-phenylhydrazones rearrange
through three different pathways (specific acid-catalysed,
uncatalysed and general base-catalysed). The different effects
of the substituents on the course of the rearrangement
in the three pathways have been examined.