Chiral scandium catalysts for enantioselective Michael reactions of beta-ketoesters.

A highly enantioselective Michael reaction of beta-ketoesters with alpha,beta-unsaturated ketones promoted by a chiral scandium catalyst has been developed. In the presence of Sc(OTf)3 and (S,S)-6,6'-bis(1-hydroxy-2,2'-dimethylpropyl)-2,2'-bipyridine, the desired Michael reactions proceeded smoothly in dichloroethane at 40 degrees C to afford the corresponding adducts in good to high yields with excellent enantioselectivities in most cases. It was found in this reaction that a lower concentration of the reaction mixture was key to attaining high enantioselectivities.