Electrophilic olefin heterocyclization in organic synthesis. Highly stereoselective synthesis of trans 3,5-disubstituted pyrrolidin-2-ones by iodolactamization via homoallylic asymmetric induction

α-Substituted γ,δ-unsaturated thioimidates, prepared by methylation of the corresponding thioamides, undergo iodine-induced lactamization to provide 3,5-disubstituted pyrrolidin-2-ones. High 1,3-asymmetric induction by the homoallylic substituents is observed in this iodolactamization. The origin of the trans diastereoselectivity of the reaction is explained by nonbonded interactions in transition states. The γ-lactams served as precursors for pharmacologically active compounds