(Z)-Selective Wittig and Corey–Chaykovsky reactions of propargyl ylides using trialkylgallium bases

Trialkylgalliums deprotonated propargylphosphonium salts and propargylsulfonium salts to form propargyl ylides. The resulted organogallium intermediates underwent the Wittig reaction and the Corey–Chaykovsky reaction with aldehydes giving (Z)-enynes and (Z)-epoxides predominantly. The use of an appropriate trialkylgallium is essential for the stereoselectivity.