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

An efficient aminofluorosulfonylation strategy was developedforthe synthesis of various pyrazoline-functionalized aliphatic sulfonylfluorides using beta,gamma-unsaturated hydrazoneswith sulfur dioxide and NFSI as the starting materials under mildconditions. The sulfonyl fluoride products could be successfully transformedinto the corresponding sulfonate esters and amides via the sulfur-(VI)fluoride exchange (SuFEx) click reactions. Preliminary mechanisticinvestigations demonstrate that the reaction operates through a radicalcyclization/SO2 insertion/fluorination cascade process.