Furanoside thioether-phosphinite ligands for Rh-catalyzed asymmetric hydrosilylation of ketones

A series of thioether-phosphinite ligands, easily prepared in a few steps from inexpensive d-(+)-xylose, were tested in the Rh-catalyzed hydrosilylation of ketones. Systematic variation of the electronic and steric properties of the thioether moiety provided useful information about the ligand parameters which control enantiodiscrimination. The results show that the enantiomeric excesses are strongly dependent on the steric properties of the substituent on the thioether moiety and on the steric properties of the substrate. High activities and good enantiomeric excesses (up to 90%) were obtained in the hydrosilylation of several aryl ketones.