ASYMMETRIC HYDROGENATION OF DIMETHYL ITACONATE CATALYZED BY RHODIUM CHELATES OF AMINOPHOSPHINE PHOSPHINITES - A KINETIC AND NMR SPECTROSCOPICAL STUDY

The asymmetric hydrogenation of dimethyl itaconate in the presence of cationic seven-membered ring aminophosphine phosphinite rhodium(I)-cyc looctadiene complexes derived from Propranolol (PROPRAPHOS-Rh derivati ves) can be described by the Michaelis-Menten kinetics, Variation of t he nitrogen substituent in the aminophosphine phosphinite moiety of th e rhodium catalyst causes a change in the concentration of the catalys t-substrate complexes. This is especially high in the case of the N-cy clohexyl derivative as follows from the Michaelis constants, P-31 NMR spectra of this compound gave signals of three catalyst-substrate comp lexes due to the different phosphorus donors: one minor- and two major complexes, A second minor-complex could not be observed, Line-shape a nalysis indicates the intramolecular interconversion between diastereo meric catalyst-substrate complexes, being in favour of the intermolecu lar processes as found already for bis(phosphinite) chelates. Copyrigh t (C) 1996 Elsevier Science Ltd