Dual Photoredox Catalysis: The Merger of Photoredox Catalysis with Other Catalytic Activation Modes

This chapter discusses the reactions that have been enabled by the merger of photoredox catalysis with organocatalytic activation modes. Photoredox catalysis not only generates the reactive radical species but also performs a key oxidation in the organocatalytic cycle. The combination of photoredox catalysis with complementary activation modes has achieved an astonishing range of notable chemical transformations. These reactions have demonstrated that photoredox catalysis can significantly benefit from the merger with organocatalysis, acid catalysis, and transitionmetal catalysis. A transformation enabled by photoredox organocatalysis is the asymmetric a-benzylation of aldehydes. The chapter then reviews the examples of synergistic photoredox catalysis with Bronsted and Lewis acids. Lewis acids have been employed in photoredox transformations of N-aryl glycine esters, with Rueping using zinc acetate to promote α-arylation with indole nucleophiles and Wu using copper(II) triflate to promote oxidative Mannich reactions. The chapter concludes with chemistry enabled by the combination of photoredox and transition metal catalysts.