Hydrosilylation of ketones catalyzed by C2-symmetric proline-derived complexes

Extracoordinate chiral hydrosilanes were generated in situ from triethoxysilane and a C-2-symmetric ligand derived from bisproline 7. In the presence of a catalytic amount of ligand 7, prochiral ketones were reduced in moderate yield with moderate enantioselectivity (up to 64% ee). Alternatively, TiF4 complexes of 7 were used to provide higher enantioselectivity and with improved yields. The copper complex of ligand 7 and Si-29 NMR data provide some Guidance as to the key factors responsible for the observed reactivity at the silicon and at the ligand centre.