Asymmetric Diels–Alder Reactions of α,β‐Unsaturated Aldehydes Catalyzed by a Diarylprolinol Silyl Ether Salt in the Presence of Water

Abstract

Water, water, everywhere: The title reaction predominantly affords the exo isomer with excellent enantioselectivity (see scheme; TMS=trimethylsilyl). The synthesis can be carried out without organic solvents and provides the products by distillation. Water increases the rate and enantioselectivity of the reaction.