Rhodium-catalyzed asymmetric olefin hydrogenation by easily accessible aniline- and pyridine-derived chiral phosphites

An aniline- and two pyridine-derived (R)-BINOL-based P,N-containing phosphite ligands have been synthesized via a one-pot procedure. Treatment of the aniline-derived ligand with 1equiv of [Rh(COD)2]BF4 yielded a mixture of a P,N-chelate complex and a biligated P-monodentate complex (exclusively obtained by treatment of the ligand with rhodium in a ratio of 2:1), while the pyridine analogues led to the corresponding P,N-bidentate complexes as unique species. For the first time, such phosphites were studied for rhodium-catalyzed enantioselective olefin hydrogenation. At room temperature, the aniline-derived ligand was found to be more active and selective compared to the pyridine analogues, which can probably be attributed to its different coordination mode and the formation of a biligated P-monodentate complex.