Ring-Closing Synthesis of Dibenzothiophene Sulfonium Salts and Their Use as Leaving Groups for Aromatic 18F‑Fluorination

Herein, we report a novel intra­molecular ring-closing reaction of biaryl thioethers that give access to highly functionalized dibenzo­thiophene sulfonium salts under mild conditions. The resulting precursors react regio­selectively with [18F]­fluoride to give [18F]­fluoro­arenes in predictable radio­chemical yields. The strategy expands the available radio­chemical space and provides superior labeling efficiency for clinically relevant PET tracers.