AMINOPHOSPHINE PHOSPHINITES OF PROPRANOLOL ANALOGS AS LIGANDS FOR RH-CATALYZED ASYMMETRIC HYDROGENATION

Chiral aminophosphine phosphinites of a series of propranolol derivati ves have been prepared and their Rh chelates tested in the asymmetric hydrogenation of standard amino acid precursors. In order to optimize the stereoselectivity of the catalyst the N-substituents of the starti ng 1,2-amino alcohols were varied to introduce various steric and elec tronic effects. Direct correlations to steric constants, values of pK( a) or data from P-31-NMR and C-13-NMR could not be discerned. This con cerns especially the pronounced difference in ee between the N-methyl 4 and N-isopropyl derivative 5. P-31 NMR spectra hint at the electroni c effect of the N-substituent.