Oximes possessing γ-, δ or ω-alkenyl substituents are cyclised by phenylselenyl bromide, or by phenylselenyl chloride and an appropriate silver salt to the corresponding cyclicnitrones; the seleno nitrones undergo facially specific cycloaddition reactions with N-methylmaleimide; bis(alk-γ,δ-enyl) ketones undergo regiospecific cyclisation and stereospecific intramolecular cycloaddition to furnish spirocyclic
Palladium(II) chloride-catalysed cascade cyclisationâcycloaddition reactions of δ-alkenyl oximes occur regio- and facially-specifically in high yield via intermediate six-membered cyclic nitrones; preliminary studies of γ-alkenyl oximes show they are reluctant to cyclise; four potential synthetic variants of the cascade process are identified and examples of two of the classes are provided.
Bis(acetonitrile) palladium (II) chloride (10 mol %) effects cyclization of δ-alkenyl oximes to nitrones which undergo in situ 1,3-dipolar cycloaddition reactions with suitable dipolarophiles to afford a range of complex isoxazolidine derived heterocycles in high yield (81–85%).