Currently, the most effective and economic way to convert an alkene into an optically active alcohol is the two-step sequence: hydrosilylation/oxidation. Much work has been devoted to elucidating effective catalysts for this process, but hitherto only one effective and highly stereoselective process has been available. Herein we present a novel catalytic system for the asymmetric hydrosilylation of aromatic alkenes, giving the products in high yields and with the highest enantioselectivity (up to 99% ee) ever observed for this reaction. The reaction works efficiently for a variety of substituted aromatic alkenes, giving access after Tamao oxidation to almost optically pure benzylic alcohols in high yields.

alcohols alcohols (benzene compounds) Q 0230 -084Highly Enantioselective Hydrosilylation of Aromatic Alkenes. -A novel catalytic system for the hydrosilylation of styrene derivatives is presented, including the chiral phosphoramidite ligands (I) or (II) with a Pd catalyst. With ligand (II), the highest enantioselectivity ever observed for the hydrosilylation of styrene (99% e.e.) is achieved. A combination of asymmetric hydrosilylation and Tamao oxidation provides access to optically active alcohols in high optical purity. A variety of electron-withdrawing or electron-donating substituents is tolerated.-(JENSEN, JAKOB F.; SVENDSEN, BO Y.; LA COUR, THOMAS V.; PEDERSEN, HENRIETTE L.; JOHANNSEN, MOGENS; J.