Thermally induced isomerisation of isoxazol-5-ylhydrazines

Abstract

The thermal isomerisation of isoxazol-5-ylhydrazines (I) led to 1-aminopyrazolin-5-ones (II), 4-aminopyrazolin-5-ones (III), and 1,2,4-triazin-6-ones (IV), in ratios depending on the nature of the substituents and the solvents used. A reaction mechanism involving a bicyclic intermediate, is suggested on the basis of the behaviour of isoxazolyl hydrazines methylated on the hydrazine moiety towards heating. Heating the methylated isoxazolyl-hydrazines (IXg and h) afforded the corresponding azirinecarbohydrazides (XII).