Dicyanopyrazine: 10th Anniversary in Photoredox Catalysis

The last decade unveiled dicyanopyrazine as a purely organic photocatalyst capable of initiating a variety of unprecedented photoredox transformations. The latest discoveries also pointed to a facile Mallory-type photocyclization of the catalyst to quinoxaline-2,3-dicarbonitrile derivative, which proved to be the active catalytic species. Its principal photochemical properties involve the absorption band covering the blue spectral region, a sufficiently long-lived triplet, and the reversible first reduction accompanied by the formation of the corresponding radical anion. Hence, two-photon photoredox catalysis via (consecutive) photoinduced electron transfer can be conveniently accomplished to either oxidize or reduce various substrates. This review summarizes the first synthetic attempts toward dicyanopyrazine catalyst, its further improvements, structural modifications, photochemical properties, and also covers the application of pyrazine-2, 3-dicarbonitirle and quinoxaline-2,3-dicarbonitrile-based photocatalysts across the photoredox catalysis.