Unlocking Reactivity of Unprotected Oximes via Green‐Light‐Driven Dual Copper/Organophotoredox Catalysis

Abstract Oximes are widely used precursors in synthetic chemistry due to their broad availability and versatile chemical properties, in which N─O bond fragmentation represents a key reactivity mode. However, these transformations typically require the use of oxygen‐protected oximes, and a general strategy to directly utilize free oximes remains challenging due to their vulnerability to side reaction pathways, rendering low tendency towards N─OH bond cleavage. Here a unified platform is reported to achieve direct cyclization of unprotected oximes with enals, as well as other coupling partners through dual copper/organophotoredox catalysis under green light irradiation. This protocol enables concurrent activation of both N─OH and α ‐C(sp 3 )─H bonds of free oximes to form multisubstituted pyridines with exceeding structural diversity and functional group tolerance. In this process, Rose Bengal serves as a hydrogen atom transfer agent to generate radical intermediates. In the meanwhile, copper catalyst activates of free oximes via single‐electron reduction‐induced N─O bond fragmentation and controls the selectivity for intermediate trapping. The synthetic utility of this approach is further demonstrated by its successful applications in late‐stage modification of biologically active compounds and rapid assembly of solvatochromic fluorescent materials.