A Novel Chiral Sulfonium Yilde: Highly Enantioselective Synthesis of Vinylcyclopropanes

A newly designed chiral sulfonium allylide, generated in situ from the corresponding sulfonium salt in the presence of KOBut, reacted with α,β-unsaturated esters, ketones, amides, and nitriles to afford trans-2-silylvinyl-trans-3-substituted cyclopropyl esters, ketones, amides, and nitriles with outstanding diastereoselectivity and excellent enantioselectivity in good to high yields. A mechanistic rationale is proposed.