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

Three-membered cyclic sulfones undergo substitution on treatment with base-electrophile mixtures, such as LDA-Me(3)SiCl and Bu(t)-P-4 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 Me(3)SiCl, 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.