A Chiral Bis-Sulfoxide Ligand in Late-Transition Metal Catalysis; Rhodium-Catalyzed Asymmetric Addition of Arylboronic Acids to Electron-Deficient Olefins

A bis-sulfoxide with a binaphthyl backbone is introduced as a readily available, chiral ligand entity in late-transition metal catalysis. Ligand p-tol-BINASO [where p-tol-BINASO is 1,1'-binaphthalene-2,2'-diyl-bis-(p-tolylsulfoxide)] is obtained in pure form in one single synthetic step from relatively cheap, commercially available starting materials. Precatalyst [{(P,R,R)-p-tol-BINASO}RhCl]2 was synthesized in high yield and structurally characterized by X-ray diffraction, and structural data were compared to the free ligand. The precatalyst shows both excellent reactivity and selectivity in the asymmetric 1,4-addition of arylboronic acids to cyclic α,β-unsaturated ketones and esters.