Silane-controlled diastereoselectivity in the tris(pentafluorophenyl)borane-catalyzed reduction of alpha-diketones to silyl-protected 1,2-Diols.

B(C(6)F(5))(3)-catalyzed bis(hydrosilylation) of alpha-diketones can give high diastereomeric excess of either meso/anti (small silanes and disilane reagents) or dl/syn (bulky silanes) silyl-protected 1,2-diols. This easily tuned diastereoselectivity is rationalized based on the classic Felkin-Anh model applied to a mechanism relying on Si-H abstraction by the electrophilic borane reagent.