Photocatalytic Three-Component Radical Addition of Aromatic Compounds

Substitution dominates benzene chemistry because σ-adducts formed during bond construction usually rearomatize. We report a photocatalytic three-component reaction that retains the σ-adduct as a 1,4-dioxygenated cyclohexadiene. A highly reactive carbonyloxy radical adds to the arene, whereas a longer lived peroxyl radical intercepts the resulting cyclohexadienyl radical before rearomatization. A reactivity-polarity analysis rationalizes the distinct requirements for entry and capture, and time-resolved electron paramagnetic resonance detects cyclohexadienyl and tert-butylperoxyl radicals under related conditions. The reaction extends to substituted, fused, and electron-rich heteroarenes and provides benzene-derived intermediates that can be converted to hydroquinone, conduritols, and inositol isomers. These results establish kinetic differentiation of radical partners as a strategy for controlling the fate of arene σ-adducts.