Arene radiofluorination enabled by photoredox-mediated halide interconversion

Positron emission tomography (PET) is a powerful imaging technology that can visualize and measure metabolic processes in vivo and/or obtain unique information about drug candidates. The identification of new and improved molecular probes plays a critical role in PET, but its progress is somewhat limited due to the lack of efficient and simple labelling methods to modify biologically active small molecules and/or drugs. Current methods to radiofluorinate unactivated arenes are still relatively limited, especially in a simple and site-selective way. Here we disclose a method for constructing C–18F bonds through direct halide/18F conversion in electron-rich halo(hetero)arenes. [18F]F− is introduced into a broad spectrum of readily available aryl halide precursors in a site-selective manner under mild photoredox conditions. Notably, our direct 19F/18F exchange method enables rapid PET probe diversification through the preparation and evaluation of an [18F]-labelled O-methyl tyrosine library. This strategy also results in the high-yielding synthesis of the widely used PET agent l-[18F]FDOPA from a readily available l-FDOPA analogue. A photoredox-mediated SNAr reaction has now been developed for the direct radiofluorination of unactivated aryl halides. A series of arenes can be radiofluorinated in a site-selective manner from readily available aryl halide precursors under mild conditions. This strategy allows efficient 19F/18F isotopic exchange, enabling rapid PET probe diversification and clinical tracer preparation.