Synthesis of atropisomeric 5,5′-linked biphenyl bisaminophosphine ligands and their applications in asymmetric catalysis

Atropisomeric 5,5′-linked biphenyl bisaminophosphine ligands 2 has been synthesized. The axial chirality of this type of ligands can be retained by macro-ring strain produced from 5,5′-linkage of biphenyl even without 6,6′-substituents on biphenyls. The Rh complex of bisaminophosphine 2a as a catalyst is effectively working in the asymmetric hydrogenation of methyl (Z)-2-acetamido-3-arylacrylates, however, for hydrogenation of arylenamide, the low enantioselectivity was observed. When the ligands applied to Pd-catalyzed allylic alkylation, it is found that ligand 2b having a longer backbone linkage is a better ligand for enantioselection in the reaction.