Asymmetric addition of diethylzinc to aldehydes catalyzed by new zinc-amides prepared by a rhodium-catalyzed asymmetric addition

A new chiral zinc-amide 2s′ was found to be an effective catalyst for the asymmetric addition of diethylzinc to aldehydes 3 through a screening method for asymmetric catalysts, in which two catalytic asymmetric reactions are connected. The chiral zinc catalyst can be readily prepared catalytically from achiral imine 1 by the chiral rhodium–diene complex mediated asymmetric addition of dimethylzinc.

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N-[(1S)-1-(2,3-Dimethoxyphenyl)ethyl]-4-methylbenzenesulfonamideC17H21O4NSEe = >99%[α]D20=-20.8 (c 0.300, CHCl3)Source of chirality: asymmetric addition catalyzed by Rh/(R,R)-Ph-bod∗Absolute configuration: (S)