Regioselective Sulfenylation of α′-CH3 or α′-CH2 Groups of α,β-Unsaturated Ketones with Heterocyclic Thiols

A rare regioselective sulfenylation of alpha'-CH3 or alpha'-CH2 bonds adjacent to alpha,beta-unsaturated ketones using dimethyl sulfoxide as an oxidant and a substoichiometric amount of aq HI as an additive is described. This methodology employs a strong acid such as aq HI or iodine and exhibits a high regioselectivity without undergoing conjugate addition, which is difficult to achieve under the cross dehydrogenative coupling method.