Abstract
This review describes the recent progress of the synthesis of P-chiral phosphine ligands and their applications in transition-metal-catalyzed asymmetric reactions. Many enantiomerically pure P-chiral phosphine ligands have been prepared by the use of phosphine-boranes as the intermediates. Among the ligands prepared hitherto, the bidentate ligands with tert-butyl groups at the phosphorus atoms exhibit remarkably high enantioinduction ability in many catalytic asymmetric reactions, particularly in rhodium-catalyzed hydrogenations. Both enantiomers of air-stable ligands, QuinoxP* and BenzP*, are produced via (R)- and (S)-tert-butylmethylphosphine-boranes. These two ligands have been successfully used not only in asymmetric hydrogenations but also in enantioselective carbon-carbon or carbon-heteroatom bond-forming reactions. Many other P-chiral phosphine ligands reported since 2001 are also described.
