Competitive Substitution Reactions at Extracoordinate Silicon during Asymmetric Hydrosilylation

Proline-derived small molecules were utilized as organic catalysts in the asymmetric hydrosilylation of ketones. Extracoordinate chiral hydrosilicates were generated in situ as shown by 29Si NMR. These active species reduce prochiral ketones enantioselectively in good yield but only moderate enantiomeric excess (up to 40%). The parameters affecting stereoselectivity have been studied in detail. By isolating some of the intermediates and …