Enantioselective Synthesis of Binaphthol Derivatives by Oxidative Coupling of Naphthol Derivatives Catalyzed by Chiral Diamine·Copper Complexes

A highly efficient process of aerobic oxidative coupling of 2-naphthol derivatives catalyzed by 1 mol % of Cu(OH)Cl·TMEDA has been developed. Enantioselective oxidative coupling of naphthols was achieved by the use of 10 mol % of chiral catalysts prepared from proline-derived diamines and cuprous chloride, affording the corresponding binaphthols in good enantioselectivities of up to 78% ee. The ester moiety at the 3-position of the substrate was found to be essential for the good asymmetric induction observed in the present coupling reaction.