Stereoselective Sc(OTf)3-Catalyzed Aldol Reactions of disubstituted Silyl Enol Ethers of Aldehydes with Acetals.

Facile and modular access to stereodefined disubstituted aldehyde derived silyl enol ethers allowed their successful application in a stereoselective aldol reaction affording the products with excellent yields and diastereomeric ratios. The counter-intuitive stereochemical behavior of this Mukaiyama aldol reaction is accounted for by a non-classical open transition state.