A ligand-accelerated chiral Lewis acid catalyst in asymmetric Michael addition of thiols to alpha,beta-unsaturated carbonyls.

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 a dducts in high yields and enantiomeric excesses. Although chiral Lewis acid s are less reactive than their original Lewis acids in many cases, ligand-a cceleration has been demonstrated in this asymmetric Michael addition react ion.