Quinones as Multifunctional Scaffolds for Oxidative, Reductive, and HAT Photocatalysis

Photoredox catalysis, which enables both electron and hydrogen atom transfer, has become a powerful tool for activating chemical bonds and synthesizing complex molecules under mild conditions. Typically, photocatalysts are optimized either for oxidative or reductive reactions within a limited redox window (less than 3.1 V) and for hydrogen atom transfer (HAT) reactions, with few frameworks capable of mediating both pathways for high redox-demanding reactions (covering more than a 5 V redox window) without requiring special conditions. Herein, we report the use of quinones as multifunctional scaffolds in light-driven redox transformations, offering access to a redox window of approximately 5 V using visible light. The quinone scaffold's versatility facilitates a wide range of radical and ionic processes under both oxidative and reductive conditions, in addition to enabling HAT reactions. By keeping the parameters, i. e. the reaction partners, constant, such transformations can be carried out under just two reaction conditions. Oxidative transformations and HAT reactions occur under ambient air, while activation of the chromophore for reductive transformations can be achieved using an inorganic base (Cs₂CO₃) via a simple acid-base deprotonation event. This dual capability highlights the potential of quinones as scaffolds to extend their utility in photoredox catalysis.