Enantioselective Alkenylation of Aldehydes with Protected Propargylic Alcohols in the Presence of a Crown Ether as an Additive

The enantioselective alkenylation of aldehydes with protected propargylic alcohols catalyzed by chiral amino thiol has been developed. The best results were obtained for the hydrozirconation-transmetallation to zinc protocol. The key element of the method is the use of crown ethers as an additive. The enantioselectivity of the reaction performed in the presence of the crown ether was substantially higher than in the absence of this additive and the enantiomer ratio reached 98:2.