Cobalt-Catalyzed Electrochemical Enantioselective Reductive Cross-Coupling of Organohalides

Transition metal-catalyzed asymmetric reductive coupling of two electrophiles has emerged as a powerful tool for carbon-carbon bond formation; however, the enantioselective reductive cross-coupling of two aryl halides has not been developed and remains a challenge. Herein, we demonstrated the enantioselective reductive cross-coupling of two aryl halides by combining cobalt catalysis with electrochemistry to afford axially chiral biaryls with good > 20:1) and enantioselectivities (up to 94% ee). This strategy could be extended to the asymmetric crosscouplings of aryl and vinyl halides to provide axially chiral non-C2-symmetric compounds with excellent > 20:1) and enantioselectivities (up to 99% ee). Density functional theory calculations and control experiments suggested that high chemo- and enan- tioselectivities could be realized by selective cathod- ic reduction of an aryl cobalt(III) species from the first oxidative addition owing to the different redox potentials. [GRAPHICS] .