Catalytic enantioselective cyanosilylation of ketones: improvement of enantioselectivity and catalyst turn-over by ligand tuning

Sterical and electronical tuning of the bifunctional catalyst 1 afforded the improved catalyst 2, which promoted the cyanosilylation of ketones with higher enantioselectivity as well as with improved catalyst turn-over with a factor of up to 10. Thus, chiral quaternary α-hydroxynitriles were obtained with excellent ee (up to 94% ee) using 1 mol% of 2 in the case of aryl ketones and 2.5 mol% of 2 in the case of aliphatic ketones.