Defluorinative C-O Coupling between Trifluoromethylarenes and Alcohols via Copper Photoredox Catalysis

Fluorine-containing compounds have shown unparalleled impacts in the realm of functional molecules, and the ability to prepare novel structures has been crucial in unlocking new properties for applications in pharmaceutical and materials science. Herein, we report a copper-catalyzed, photoinduced defluorinative C-O coupling between trifluoromethylarenes and alcohols. This method allows for direct access to a wide selection of difluorobenzylether (ArCF₂OR) molecules, including a compound displaying liquid crystal behavior. Through slight modification of the protocol, we were able to generate difluorobenzyliodide (ArCF₂I) products, another class of synthetically useful fluorine-bearing molecules. Mechanistic investigations first suggested that ArCF₂I can serve as a reservoir to steadily supply the key ArCF₂⋅ radical species. Furthermore, experimental evidence supported a mechanism consisting of two collaborative cycles: C-F activation operated by a homoleptic Cu(I) coordinated by two bisphosphine ligands as the photocatalyst and C-O coupling promoted by a Cu(I) ligated by a single bisphosphine ligand. The critical roles of the two salt additives, lithium iodide and zinc acetate, in orchestrating the two cycles were also elucidated. This dual-role copper catalyst demonstrates the power of base metal photoredox catalysis in achieving both substrate activation and chemical bond formation via a single catalytic system.