Nickel-Catalyzed Asymmetric Ullmann Coupling for the Synthesis of Axially Chiral Tetra-ortho-Substituted Biaryl Dials

The first example of nickel-catalyzed asymmetric Ullmann coupling of bis-ortho-substituted arylhalides is described. With the chiral BINOL-based monodentate phosphoramidite ligand, the reaction allows atropoenantioselective synthesis of a series of axially chiral tetra-ortho-substituted biaryl dials. By taking advantage on this asymmetric Ullman coupling as a key stereogenic axis-forming reaction, the formal synthesis of (+)-isoschizandrin was accomplished.