Enantioselective conjugate addition of dialkylzinc to cyclic enones catalyzed by chiral binaphthyldiamine–copper(I) complexes

The enantioselective conjugate addition of dialkylzinc (R2Zn) to cyclic enones was examined using chiral binaphthyldiamine–copper(I) catalysts. Under the present reaction conditions, chiral C2-symmetric [RZn(II)]2-diamine–Cu(I) complexes were formed from chiral binaphthyldiamine, R2Zn, and copper(I or II) chloride in situ. The reaction of 2-cyclohexenone with Et2Zn proceeded smoothly in the presence of the corresponding chiral copper(I) complex (5 mol %) and achiral 2,6-diphenylaniline (10 mol %), and the desired Et-adduct was obtained with up to 76% ee in 95% yield.