Photoredox and Electrochemical Methods for C-N Bond Forming Reactions
C-N bonds are ubiquitous in medical, pharmaceutical, and natural products. Therefore, it is important to develop synthetic procedures that both effectively form C-N bonds and incorporate sustainable principles. These principles include the use of renewable energies sources such as sunlight, utilization of abundant transition metal catalysts, and increasing the atom economy of the reactions. Along these lines, we have utilized dual photoredox system capable of accessing diaryl amines, amines containing aliphatic groups, and tertiary amines nickel catalysis to perform aryl-amine cross-coupling reactions. Until very recently this class of C-N bond forming reactions were limited to Pd-catalyzed reactions. Our system is the first Ni-catalyzed reaction system capable of synthesizing diaryl amines, tertiary amines, and amines containing aliphatic groups. Mechanistic studies support an amine-radical-based reaction pathway that allows for the access to the range of products. Furthermore, we have developed an “anion pool” electrochemical method for the synthesis of N-substituted heterocycles. This base-free and transition-metal-free approach exhibits good atom economy and has proven widely applicable for the synthesis of substituted benzimidazoles.