Iodosulfonation of alkenes with benzenesulfinic acid – N-iodosuccinimide — Facile preparation of α,β-unsaturated sulfones

Reaction of alkenes and alkenols with N-iodosuccinimide (NIS) and benzenesulfinic acid in dichloromethane at room temperature affords vic-iodophenylsulfonyl adducts in good to high yields. Treatment of the iodosulfones with neutral alumina in dichloromethane at room temperature results in dehydroiodination to give the corresponding vinyl sulfones in high yield and purity by this convenient two-step procedure. Application of the iodosulfonation–dehydroiodination sequence to allylic alcohols and silyl ethers gave γ-oxygenated, α,β-unsaturated phenylsulfones, while the attempted iodosulfonation of glycals, as intermediates to vinyl sulfones, resulted in addition of benzenesulfinic acid with double bond shift (Ferrier rearrangement). Key words: iodosulfonation, vinyl sulfones, benzenesulfinic acid, N-iodosuccinimide, dehydroiodination.