Asymmetric Diels-Alder Reactions of alpha,beta-Unsaturated Aldehydes Catalyzed by a Diarylprolinol Silyl Ether Salt in the Presence of Water

摘要

The Diels-Alder reaction is a powerful synthetic method for the construction of regio-and stereochemically defined cyclohexane frameworks.There are several catalytic enantio-selective methods,and MacMillan and co-workers developed the first Diels-Alder reaction involving an organo-catalyst,which proceeds by a LUMO-lowering activation mechanism.Since then several asymmetric Diels-Alder reactions involving organocatalysts have been reported.Our group and that of Jorgensen developed a diarylprolinol silyl ether as an effective organocatalyst in 2005,and this type of catalyst has since been employed widely in several asymmetric reactions.Recently,we found that diarylprolinol silyl ether 1 combined with CF3CO2H is an effective Diels-Alder catalyst in toluene.