New chiral phosphite catalysts for asymmetric hydrosilylation

Ligand L I was obtained by the reaction of the diisopropyl ester of (+)-tartaric acid with P(NMe2)2OEt in i:i mole ratio at 120~ Ligand L 2 was obtained by the reaction of the (-)-menthol with di(o,o-di-tert-butyl-p-methyl)phenyl chlorophosphite in absolute benzene at 0~ Both these compounds were characterized by IH, 13C, and 31p NMR and IR spectroscopy and physicochemical indices. Catalysts were obtained in situ from [Rh(COD)CI]z and [RH(CO)2CI]z with L I and L 2. The experiments were carried out in a reactor maintained at constant temperature in an argon atmosphere. The experiment indicated by an asterisk was carried out in CCI 4. The other reactions were carried out without solvent. As shown previously, the reaction temperature and acetophenone:rhodium (AP/Rh) and ligand:rhodium (L*/Rh) ratios affect the enantioselectivity of the catalyst [2]. The results are given in Fig. I. l-Phenylethanol was obtained when the reaction was carried out with the rhodium complexes with L I in optical yield up to 23%. This is the first example of the successful use of phosphite complexes in asymmetric hydrosilylation.