High-valent sulfur fluorides as reactivity switches for PFAS-free benzene–azepine skeletal editing

Abstract

The development of non-PFAS fluorinated heterocycles is a critical challenge in sustainable molecular design. Here we report a reactivity-switching skeletal editing strategy that transforms benzenes into azepines through visible-light activation mediated by high-valent sulfur fluorides. The pentafluorosulfanyl (SF₅) and tetrafluorosulfanyl (SF₄) groups act as powerful electronic activators that stabilize singlet nitrenes, lowering the barrier for 6π-electrocyclization and enabling efficient benzene-to-azepine interconversion in high yields. Mechanistic and DFT studies reveal that the strong electron-withdrawing capacity of SF₅/SF₄ is key to promoting this transformation. Importantly, SF₅ and SF₄ motifs are PFAS-free fluorine architectures that retain the beneficial physicochemical properties of perfluoroalkyl groups while avoiding environmental persistence. This work establishes a sustainable and general strategy for fluorinated skeletal editing, offering a foundation for future design of PFAS-free agrochemical, medicinal, and materials scaffolds.