Reactions of Stable Wittig Reagents with Episulfides

Abstract Stable Wittig reagents effectively reacted with episulfides to afford dialkyl fumarates and dialkyl maleates in good yields. The reaction probably occurred via attack of the ylide carbanion on episulfide’s sulfur to form a thiocarbonyl intermediate. The ylide further attacked this thiocarbonyl intermediate to give the final olefins.