Visible Light-Induced Pd-Catalyzed Heck Reactions

Heck reaction is regarded as one of the most powerful and practical synthetic tools to construct C-C bonds, and has gained increasingly widespread applications in the synthesis of various functional molecules over the past decades. As an emerging strategy for the formation of C-C bonds, visible light-induced Pd-catalyzed Heck reaction has tremendously extended the scope of substrates, in both aspects of nucleophiles and electrophiles. This unique transformation, triggered by photoexcited Pd-0 and mechanistically involving hybrid radical-Pd-1 species, features mild conditions, excellent functional compatibility and transformational diversity, which greatly complements classical Heck reaction catalyzed by ground-state Pd complexes. These advantages will render visible light-induced Heck reaction widespread applications in the synthesis of functional molecules and late-stage modification of structurally complex compounds. According to the species of nucleophiles/electrophiles and types of cascade reactions, visible light-induced Heck reactions are logically classified, and some of the elusive reaction mechanisms are also illustrated.