Enantioselective hydrosilation of ketones in the presence of an S,S-[1,2-bis(tetrahydroindenyl)ethane]-titanium catalyst

Abstract

S,S-[1,2-Bis(tetrahydroindenyl)ethane]titanium-based catalysts were used, in conjunction with either diphenyl- or methylphenylsilane, to effect the catalytic hydrosilation of a wide variety of dialkyl ketones. The highest enantioselectivity was observed with c-pentylethylketone (70%) and the selectivity was found to be very sensitive to the steric qualities of the alkyl groups, e.g., iPr-Me (15%), iPr-Et (65%), iPr-nPr (60%). Inclusion of a coordinating heteroatom in the alkyl group of the ketone substrate, or carrying out the reaction in a coordinating solvent such as THF, had no significant effect on the rate or selectivity of the reaction. Keywords: hydrosilation, enantioselective catalysis, ketones, ansa-metallocenes.