Substrate‑Driven Iridium Photocatalysts Enable Diastereoselective Dearomative Polyoxygenation of Hydroxyquinolines

Abstract

We report a novel strategy for the direct, diastereoselective dearomative polyoxygenation of 8-hydroxyquinolines, leverag-ing 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 pre-catalyst 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 reac-tion proceeds via selective oxygen insertion into the coordinated quinoline, followed by water-assisted hydroxylation, yield-ing 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.