Access to 2′-Substituted Binaphthyl Monoalcohols via Complementary Nickel-Catalyzed Kumada Coupling Reactions under Mild Conditions: Key Role of a P,O Ligand

Two complementary Kumada coupling methods for the conversion of monotriflated 1,1'-binaphthalene-2,2'-diol (BINOL) into 2'-substituted binaphthyl monoalcohols under mild conditions are reported. A protocol using NiCl2(dppe), in combination with an improved preparation of the monotriflate, is effective for 1,1'-binaphthalene-2-ols containing unsubstituted or electron-poor aryl or benzyl 2'-substituents. An alternative procedure, using a potentially hemilabile-bidentate phosphinan-4-ol ligand, is superior for products containing neopentyl or electron-rich aryl 2'-substituents. The obtained binaphthyl alcohols represent potentially useful synthons for chiral ligands and auxiliaries.