Asymmetric Hydrogenation of Aromatic, Aliphatic, and α,β‐Unsaturated Acyl Silanes Catalyzed by Tol‐binap/Pica Ruthenium(II) Complexes: Practical Synthesis of Optically Active α‐Hydroxysilanes

A catalytic system of RuII complex (see scheme; Ar=4-CH3C6H4; R=H, t-C4H9) and t-C4H9OK or NaBH4 activator has been used in the hydrogenation of aromatic and aliphatic acyl silanes to give α-hydroxysilanes with high enantioselectivity (R1=aryl, alkyl, alkenyl; R2=t-C4H9, C6H5). Optically active allylic α-hydroxysilanes are obtained in the 1,2-reduction of α,β-unsaturated acyl silanes. These chiral α-hydroxysilanes are converted into 4-substituted 2-cyclopentenones without loss of enantioselectivity.