Ultrafast Single Electron Transfer Enables General Visible Light C─X (S, SS, Se) Coupling via Carbonyl Activation

The formation of carbon─heteroatom bonds is a key strategy that enables the modular construction of molecules in synthetic chemistry, but activating inert carbonyl compounds to forge C─X bonds remains a longstanding synthetic challenge. Herein, we report a universal visible light-driven photocatalytic system that enables efficient C─X (X = SS, S, Se) bond formation under mild, redox-neutral conditions. Guided by Marcus electron transfer theory, we employed a computational redox-pair screening strategy to identify triplet-state pathways with optimal electronic coupling matrix element (H_if) and thermodynamic alignment. High-level multireference calculations confirmed an ultrafast single-electron transfer mechanism with ultrafast kinetics approaching the diffusion limit. To translate this mechanistic insight into a functional platform, we designed a dual-functionalization strategy for α-diketones, wherein one carbonyl acts as a conventional synthon while the other forms a light-responsive dihydroquinazolinone (DHQZ) radical precursor. This system exhibits broad substrate scope, excellent functional group tolerance, and compatibility with late-stage functionalization of bioactive scaffolds. Overall, this study establishes a general and mechanistically predictive photocatalytic strategy that transforms Marcus theory from a conceptual foundation into a design principle for efficient, light-driven C─heteroatom bond construction.