Oxidation of 2-phenylhydrazono-γ-butyrolactone: a novel ring expansion rearrangement leading to tetrahydro-1,3-oxazine-2,4-dione derivatives

Abstract

2-Hydroxy-2-phenylazo-γ-butyrolactone 3a, prepared from oxidation of phenylhydrazone 1a, either decomposes to form α-keto-γ-butyrolactone 2a in 80% yield or rearranges to tetrahydro-1,3-oxazine-2,4-dione derivative 4a in 95% yield under different conditions.