Heterocyclic rearrangements. Synthesis and reactivity of oximes of some 3-acylisoxazoles. A reinvestigation

Abstract

The oximation reaction of some 3-acylisoxazoles with hydroxylamine hydrochloride and the geometry of the product oximes were reinvestigated. 3-Benzoylisoxazoles gave mixtures of (E)- and (Z)-isomers, whereas 3-acetylisoxazoles gave (E)-isomers only. The base-induced rearrangement of 3-acylisoxazole oximes to 1,2,5-oxadiazoles (furazans) was reinvestigated and was shown to depend on the geometry of the oximes since, when treated with aqueous potassium hydroxide, only (Z)-oximes readily rearranged.

On the basis of our findings, some discrepancies in the literature have been corrected.