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 cyclic nitrones; 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 products.
