Effects of Molecular Oxygen, Solvent, and Light on Iridium-Photoredox/Nickel Dual-Catalyzed Cross-Coupling Reactions

In order to achieve reproducibility during iridium-photoredox and nickel dual-catalyzed sp(3)-sp(2) carbon-carbon bond-forming reactions, we investigated the role that molecular oxygen (O-2), solvent and light-source (CF lamp or blue LED) play in a variety of Ir-photoredox mediated transformations. The presence of O-2 was discovered to be important for catalyst activation when air-stable Ni(II) precatalysts were used in DMF under CF lamp irradiation; however, O-2 was not required for catalysis when conducted with Ni(COD), in the same reaction system. O-2 is believed to promote rapid reduction of the Ni(II) precatalyst by Ir(II) to Ni(0). In addition to O-2, the effects that solvent and light-source have on the dual-catalyzed decarboxylative cross-coupling reactions will be discussed. These findings have enabled us to develop a more robust dual-catalyzed decarboxylative cross-coupling protocol.