A new approach to switching of enantioselectivity in NHC-Cu-catalyzed conjugate addition of alkylzincs to cyclic enones

Conjugate addition of Et2Zn to 2-cyclohexen-1-one catalyzed by Cu(OTf)(2) combined with an azolium salt derived from (S)-leucinol produced the corresponding (S)-adduct, while the use of Cu(acac)(2) in combination with the same ligand afforded the (R)-adduct as a major product.