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

Abstract

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 for this significant transformation is the strong affinity of cyanide for metal centers, which makes organometallic catalysis elusive by hampering oxidative addition and reductive elimination. Herein, we demonstrate for the first time that nickel-catalyzed cyanations of aryl halides are readily enabled by visible-light photoredox catalysis, in which Ni(II) species are transiently oxidized to Ni(III) species, thereby facilitating the subsequent cyanide transfer and reductive elimination. Using this dual catalysis strategy, we cyanated aryl and alkenyl halides at room temperature in a highly benign manner (30 examples, 53-93% yields) by avoiding the use of air-sensitive ligands, Ni(0) processors, and hypertoxic cyanation reagents, while also not generating excess metal waste. Computational studies were also used to help understand the present transformation.