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

An enantioselective C(sp(3))-C(sp(3)) cross-coupling of racemic alpha-silylated alkyl iodides and alkylzinc reagents is reported. The reaction is catalyzed by NiCl2/(S,S)-Bn-Pybox and yields alpha-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 (alpha-silicon effect). Both coupling partners can be, but do not need to be, functionalized, and hence, even alpha-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 alpha-chiral silanes.