Substrate-driven iridium photocatalysts enable diastereoselective dearomative polyoxygenation of hydroxyquinolines

We report a novel strategy for the direct, diastereoselective dearomative polyoxygenation of 8-hydroxyquinolines, leveraging a substrate-coordinated Ir(iii) complex as a self-activating photocatalyst under visible light and atmospheric oxygen. In this system, the hydroxyquinoline substrate coordinates to the Ir precatalyst generating an Ir-oxyquinolate complex. This species activates the substrate and acts as a photosensitizer, promoting the generation of singlet oxygen and enabling the formation of multiple C-O bonds in a single step with excellent regio- and stereocontrol. Mechanistic investigations, including ligand exchange experiments, control reactions, and DFT studies, reveal that the reaction proceeds via selective oxygen insertion into the coordinated quinoline, followed by water-assisted hydroxylation, yielding structurally complex polyoxygenated products. This substrate-driven approach eliminates the need for external photo-catalysts and demonstrates a unique strategy for the activation of heteroaromatic substrates, providing access to motifs of potential relevance in pharmaceuticals and functional materials. This work highlights how substrate-metal cooperation can be exploited to achieve transformations that are challenging or inaccessible with conventional photocatalytic systems.