Chiral Lewis acid-catalyzed enantioselective intramolecular carbonyl ene reactions of unsaturated α-keto esters

Chiral Lewis acid-promoted highly enantioselective intramolecular carbonyl ene reactions of unsaturated a-keto esters have been investigated. In the presence of chiral Lewis acids such as [Sc((R,R)-Ph-pybox)](OTf)(3) and [Cu((S,S)-Ph-box)](OTf)(2), several unsaturated a-keto esters underwent carbonyl ene reactions in CH2Cl2 at room temperature to give monocyclic products in good yield and excellent enantioselectivity.