Aromatic Chemistry in the Excited State: Facilitating Metal-Free Substitutions and Cross-Couplings.

Transition-metal-catalyzed cross-couplings between aromatic electrophiles and nucleophiles have revolutionized modern chemical syntheses. Nevertheless, transition-metal-free approaches are preferable, considering the various issues caused by metal catalysts. This Minireview summarizes the recent progress in the light-enabled transition-metal-free formation of carbon-carbon and carbon-heteroatom bonds in aromatics, which opens a new avenue in aromatic reactions. From the mechanistic perspective, it classifies different reaction types of aryl electrophiles in an excited state with various nucleophiles. We believe this will provide more rationales for metal-free aromatic substitutions and cross-couplings with light, and guide the development of novel transformations of aromatic compounds facilitated by light.