Intramolecular cyclisation of phenolic oximes. Part I. Cyclisations with manganese(III) tris(acetylacetonate)

Reactions of a series of p-hydroxyarylpropan-2-one oximes with manganese(III) tris(acetylacetonate) resulted in intramolecular cyclisation to the corresponding spiro-isoxazolines by a two-electron oxidation in which an incipient phenoxonium ion is trapped by the oxime hydroxy-group. o-Hydroxyarylpropan-2-one oximes did not react in this way but gave instead benzofurans and the parent ketones.