A ligand-accelerated chiral Lewis acid catalyst in asymmetric Michael addition of thiols to α,β-unsaturated carbonyls

Abstract

A novel chiral hafnium catalyst, which was readily prepared from Hf(OTf)4 and chiral ligand 1, has been developed in asymmetric Michael reactions of thiols with 3-(2-alkenoyl)-2-oxazolidinones, affording the corresponding adducts in high yields and enantiomeric excesses. Although chiral Lewis acids are less reactive than their original Lewis acids in many cases, ligand-acceleration has been demonstrated in this asymmetric Michael addition reaction.