Chiral Phosphine−Phosphite Ligands in the Highly Enantioselective Rhodium-Catalyzed Asymmetric Hydrogenation

We have investigated a series of enantiopure phosphine−phosphite ligands (P1−P2 = ligands 1−4) in the rhodium-catalyzed asymmetric hydrogenation reaction. Intermediate [Rh(P1−P2)(cod)]BF4 and [Rh(P1−P2)(5)]BF4 complexes (cod = 1,5-cyclooctadiene; 5 = methyl acetamidoacrylate ester) were observed by 31P{1H} NMR. The [Rh(P1−P2)(cod)]BF4 complexes were precursors to active catalysts of the asymmetric hydrogenation reaction of several prochiral dehydroamino acid derivatives under mild reaction conditions (1 bar of hydrogen and 20 °C). The enantiomeric excess reached up to 99%.