The asymmetric conjugate addition of diethyl zinc to acyclic enones is described. With 1% Cu(OTf)2 and 2% of a chiral phosphite ligand, the catalyst allowed ee's up to 92'% to be obtained. The addition of dimethyl zinc to a macrocyclic 15-membered ring enone lead to optically active R-(-)-muscone, in 53% yield and 79% enantiomeric excess.