Aminofluorosulfonylation of β,γ-Unsaturated Hydrazones with Sulfur Dioxide and N-Fluorobenzenesulfonimide: Accessing Pyrazoline-Functionalized Aliphatic Sulfonyl Fluorides.

An efficient aminofluorosulfonylation strategy was developed for the synthesis of various pyrazoline-functionalized aliphatic sulfonyl fluorides using β,γ-unsaturated hydrazones with sulfur dioxide and NFSI as the starting materials under mild conditions. The sulfonyl fluoride products could be successfully transformed into the corresponding sulfonate esters and amides via the sulfur(VI) fluoride exchange (SuFEx) click reactions. Preliminary mechanistic investigations demonstrate that the reaction operates through a radical cyclization/SO2 insertion/fluorination cascade process.