Synthesis of C2-symmetric P-chiral bis(phosphine borane)s and their application in rhodium(I) catalyzed asymmetric transformation

A new development for the synthesis C₂-Symmetric P-Chiral Bis(phosphine borane) ligands is reported. These ligands are based on the asymmetric induction of prochiral phosphine ligands with organolithium/chiral diamine complexes. These ligands have been evaluated in asymmetric rhodium(I) catalyzed hydrogenation and [4+2] cycloisomerization reactions. Enantiomeric excesses as high as 99% were obtained for ene-diene cycloadditions.