Photoredox Catalysis Unlocks the Nickel-Catalyzed Cyanation of Aryl Halides under Benign Conditions

The transition-metal-catalyzed cyanations of aryl halides are among the most used methods for synthesizing aryl nitriles. Despite tremendous advances, cyanating an aryl halide in a facile and benign fashion has generally been unsuccessful. The challenge in this significant transformation is the strong affinity of cyanide for metals, which hampers oxidative addition (OD) and reductive elimination (RE) making organo-metallic catalysis elusive. Herein, we demonstrate for the first time that photoredox-nickel-catalyzed cyanations of aryl halides are readily enabled by visible light, in which Ni(II) species are transiently oxidized to Ni(III) species, thereby facilitating subsequent cyanide transfer and RE. Using this dual catalysis strategy, we cyanated aryl and alkenyl halides at room temperature in a highly benign manner (30 examples, 53-93% yield) by avoiding the use of air-sensitive ligands, Ni(O) precursors, and hypertoxic cyanation reagents, while also limiting excess metal waste. Computational studies were also used to help understand the present transformation. [GRAPHICS] .