Enantioselective Reduction of Prochiral Ketones using Spiroborate Esters as Catalysts.

Novel spiroborate esters derived nonracemic 1,2-aminoalcohols and ethylene glycol are reported as highly effective catalysts for the asymmetric borane reduction of a variety of prochiral ketones with borane-dimethyl sulfide complex at room temperature. Optically active alcohols were obtained in excellent chemical yields using 0.1 to 10 mol % of catalysts with up to 99% ee.