Electrophilic alkene sulfenylation with sulfinate esters.

An electrophilic alkene sulfenylation using sulfinate esters as readily available sulfur sources has been developed under mild HI activation. Terminal and 1,2-disubstituted alkenes, including cyclic substrates, predominantly undergo electrophilic addition to afford β-alkoxysulfides with high regio- and stereoselectivity. In contrast, 1,1-diarylethenes favor electrophilic substitution to give alkenyl sulfides selectively. Control experiments and Hammett analyses reveal that sulfinate esters serve as precursors to sulfur(II) electrophiles and that episulfonium ion formation constitutes the rate-determining step. These findings establish a systematic mechanistic framework for substrate-dependent divergence between electrophilic addition and substitution pathways.