X=Y-ZH systems as potential 1,3-dipoles. Part 31. Generation of nitrones from oximes, background and scope of the tandem 1,2-prototropy-intramolecular cycloaddition sequence

Article abstract of DOI:10.1016/S0040-4020(01)86441-3

1,2-Prototropy in aryl and aliphatic oximes generates a small equilibrium concentration of the corresponding NH nitrone. Examples of a tandem 1,2-prototropy-intramolecular cycloaddition sequence involving aryl and aliphatic oximes are described and steric and electronic factors that favour or disfavour such a sequence are discussed. Deuterium labelling studies with an aliphatic oxime rule out the involvement of an enehydroxylamine in the prototropic generation of the NH nitrone.