Remote Nickel-Catalyzed Cross-Coupling Arylation via Proton-Coupled Electron Transfer-Enabled C-C Bond Cleavage.

Abstract

Cross-coupling reactions for carbon-carbon and carbon-heteroatom bond formation are of great importance in modern chemical synthesis. In addition to classical cross-couplings involving preformed or preactivated coupling partners, more recently breakthroughs have been made in the selective, direct coupling of abundant aliphatic carbon-hydrogen bonds using hydrogen atom transfer reactions in which the bond-dissociation energy is the thermodynamic driving force. The more challenging carbon-carbon bond activation is still rather underdeveloped due to the bond inertness. Herein, we report a mild and general strategy for the activation of a diverse set of readily available cyclic alcohols for the remote and site-specific arylation of ketones via the combination of photoredox-mediated multisite concerted proton-electron transfer (MS-PCET) and nickel catalysis. The current cross-coupling proceeds with the generation of an alkoxy radical utilizing bond-dissociation free energy (BDFE) as the thermodynamic driving force. Subsequently, the resulting remote carbon-centered radicals formed by C-C cleavage merge with the nickel catalytic cycle to create the challenging C(sp3)-C(sp2) bonds.