The Asymmetric Piers Hydrosilylation.

An axially chiral, cyclic borane decorated with just one C6F5 group at the boron atom promotes the highly enantioselective hydrosilylation of acetophenone derivatives without assistance of an additional Lewis base (up to 99% ee). The reaction is an unprecedented asymmetric variant of Piers' B(C6F5)(3)-catalyzed carbonyl hydrosilylation. The steric congestion imparted by the 3,3'-disubstitutecl, binaphthyl backbone of the borane catalyst as well, as the use of reactive trihydrosilanes as reducing agents are keys to success.