Enantioselective Construction of α-Chiral Silanes by Nickel-Catalyzed C(sp3 )-C(sp3 ) Cross-Coupling.

An enantioselective C(sp3 )-C(sp3 ) cross-coupling of racemic α-silylated alkyl iodides and alkylzinc reagents is reported. The reaction is catalyzed by NiCl2 /(S,S)-Bn-Pybox and yields α-chiral silanes with high enantiocontrol. The catalyst system does not promote the cross-coupling of the corresponding carbon analogue, corroborating the stabilizing effect of the silyl group on the alkyl radical intermediate (α-silicon effect). Both coupling partners can be, but do not need to be, functionalized, and hence, even α-chiral silanes with no functional group in direct proximity of the asymmetrically substituted carbon atom become accessible. This distinguishes the new method from established approaches for the synthesis of α-chiral silanes.