Episulfone substitution and ring-opening reactions via α-sulfonyl carbanion intermediates

Abstract

Three-membered cyclic sulfones undergo substitution on treatment with base–electrophile mixtures, such as LDA–Me₃SiCl and Bu^t–P₄ phosphazene base–PhCHO, to give either substituted episulfones or the corresponding alkenes following loss of SO₂. The structure of a trisilylated episulfone product, 2a, was determined by X-ray crystallography. In the absence of Me₃SiCl, reaction of episulfones with lithium diisopropylamide results in ring-opening to give alkenyl sulfinate intermediates, which can be alkylated to give (E)-alkenyl sulfone products in stereoselective fashion.