Photosensitized Gold-Catalyzed Cross-Couplings of Aryl Bromides

Recently, ligand-promoted Au(I)/Au(III)-catalyzed cross-coupling reactions with aryl iodides have garnered considerable attention. Here, we report the first visible-light-driven gold-catalyzed cross-couplings of challenging aryl bromides. In the presence of a (P, N)-gold(I) catalyst and an acridinium photocatalyst under blue LED irradiation, C-O coupling of aryl bromides with carboxylic acids was achieved, and soon it was found that this photoinduced gold-catalyzed cross-coupling of aryl bromides was appliable for other C-C, C-N, and C-S bond formation. Experimental and computational studies suggest that this visible-light-driven gold-catalyzed cross-couplings of aryl bromides involves two discrete photoinduced energy transfer (EnT) events: first, energy transfer (EnT) from a photosensitizer produces an excited-state gold(I) complex that allows the bottleneck oxidative addition of aryl bromides to form an aryl Au(III) complex and second, the reductive elimination of aryl-Au(III) complex to regenerate Au(I). Collectively, the new synergistic catalytic method developed here highlights the tremendous potential of photochemical gold catalysis via excited-state organogold complexes, as well as its potential to facilitate drug discovery due to the biocompatibility and mildness of the reaction conditions.