Resolution of Pd catalyst with tropos biphenylphosphine (BIPHEP) ligand by DM-DABN: asymmetric catalysis by an enantiopure BIPHEP-Pd complex.

[reaction: see text] The racemic Pd complex with the chirally flexible (tropos) biphenylphosphine (BIPHEP) ligand can be resolved with enantiopure 3,3'-dimethyl-2,2'-diamino-1,1'-binaphthyl (DM-DABN) as a resolving agent at room temperature. The enantiopure BIPHEP-Pd complex is obtained from complexation with enantiopure DABN followed by tropo-inversion into the single BIPHEP-Pd diastereomer at 80 degrees C and protonation at 0 degrees C. The enantiopure BIPHEP-Pd complex can be used as an efficient Lewis acid catalyst for the Diels-Alder reaction at room temperature to give high enantioselectivity (82% ee, 60%).