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

(Chemical Equation Presented) A catalytic system of RuII complex (see scheme; Ar = 4-CH3C6H4; R = H, t-C 4H9) and t-C4H9OK or NaBH 4 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. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.