Chalcogenide–Lewis Acid Mediated Tandem Michael Aldol Reaction — an Alternative to the Morita–Baylis–Hillman Reaction and a New Development

Abstract

AbstractA tandem Michael aldol reaction mediated by a chalcogenide and Lewis acid was developed in three different types. Reactions of electron‐deficient alkenes with aldehydes or α‐keto esters in the presence of a sulfide and TiCl4 gave α‐chloromethyl aldols. Reactions of chalcogenide–enones with carbonyl compounds gave α‐(α‐hydroxyalkyl)enones (Mori‐ta–Baylis–Hillman adducts) after the work‐up of the reaction mixture with triethylamine. The intramolecular Michael aldol reactions of N‐enoylthioamides with aldehydes in the presence of BF3Et2O produced tricyclic compounds bearing a bridgehead bound to four heteroatoms and induced four stereocenters in one step, three of which were consecutive. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)