Self‐Assembly of a Chiral Bis‐phosphine Ligand Bearing Pyridyl Crown Ethers and Chiral Primary Ammoniums: Application to Catalytic Asymmetric Hydrogenation Reactions

Abstract A chiral bis‐hosphine ligand bearing two pyridyl crown ethers was complexed with primary ammonium salts of different absolute configuration to form supramolecular chiral catalysts, which were successfully applied in the Rh‐catalyzed asymmetric hydrogenation of α‐dehydroamino acid esters and Ir‐catalyzed asymmetric hydrogenation of quinoxalines. By comparison with the non‐assembled catalysts, the complexation between the chiral catalysts and primary ammoniums obviously improved enantioselectivities. Up to 11 % enhancement in ee values in asymmetric hydrogenation of α‐dehydroamino acid esters and 30 % enhancement in ee values in asymmetric hydrogenation of quinoxalines were achieved.