Diphenoquinone-Catalyzed Dual HATs Enable Visible Light-Induced Sequential Dehydrogenation of Amides to Enamides

Diphenoquinones (DPQs) were developed as a type of photocatalyst capable of dual hydrogen atom transfer (HAT) within a single catalytic cycle. This capability arises from the specific conjugated π-system of DPQs, which enables radical resonance from the ketyl carbon-centered position to the oxygen-centered position for the generation of a dioxygen-centered radical species. This strategy was successfully exploited in the photochemical dehydrogenation of amides to enamides by sequential abstraction of α-C(sp3)–H and β-C(sp3)–H, offering broad substrate scope and high regioselectivity under mild conditions.