Non-regiospecific additions of enamines to αβ-unsaturated sulphones

Abstract

αβ-Unsaturated sulphones react with 1-pyrrolidino-cyclopentene and -cyclohexene to give, after hydrolysis, the corresponding 2-(sulphonylalky)cycloalkanones. When the vinyl sulphone system carries no substituents or only a β-methyl group, only the expected normal product, derived from nucleophilic attack of the enamine on the β-position of the olefin, is obtained, i.e. the reaction is regiospecific. In contrast, sulphones bearing a β-phenyl group afford two isomeric 2-(sulphonylalkyl)cycloalkanones, in which C-2 is linked to either the β- or the α-carbon atom of the staring sulphone.