Enantioselective conjugate addition of diethylzinc to cyclic enones catalyzed by copper complexes of methylene-bridged P-chirogenic diphosphines.

The copper-catalyzed enantioselective conjugate addition of diethylzinc to 2-cyclohexen-1-one was investigated using (R,R)-bis-(t-butylmethylphosphino)methane (1c) as a chiral ligand. The reaction was carried out at 0 degrees C in THF-toluene as the solvent system and in the presence of 1.2 mol% of CuOTf afforded (S)-3-ethylcyclohexan-1-one with 85% ee.