Phosphine-based copper 1.4- conjugate additions

In 2004, excellent enantioselectivities of up to 98% ee were obtained by Morimoto et al. by using a phosphine-sulfonamide-containing 1,1 -binaphthyl-based ligand in the enantioselective copper-catalysed conjugate addition of ZnEt2 to several benzylideneacetones (Scheme 2.27). Similar levels of enan-tioselectivity (up to 97% ee) combined with excellent yields (up to 90%) were obtained by Leighton et al. for the copper-catalysed enantioselective addition of various alkylzincs to cyclic enones performed in the presence of other chiral phosphine-sulfonamide ligands (Scheme 2.27). ... 

A phosphine-Schiff base ligand (17) has been used for copper-catalysed asymmetric conjugate addition of diethylzinc to various ( )-alkenyl aryl ketones where the aryl ring is either a phenyl group substituted by nitro, chloro, or methoxy groups or not substituted or a naphthyl group. When the conjugate addition has been performed in ethyl acetate... 

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