4-Fluorobenzenesulfonyl chloride → 4-Fluorobenzenesulfonyl fluoride

To a solution of compound 4-Fluorobenzenesulfonyl chloride (50 g, 0.256 mol) in ACN (500 mL) was added KF (74.36 g, 5 eq) and 18-crown-6 (2 g) at r.t., then the mixture was stirred at r.t. overnight. The mixture was detected by LC-MS, then saturated aqueous NaHCO3 was added and the mixture was extracted with EtOAc, the organic layer was washed with saturated aqueous NaHCO3, brine, dried over anhydrous Na2SO4, concentrated to give the crude compound 4-Fluorobenzenesulfonyl fluoride (46.70 g) as pale yellow oil which was used for the next step without further purification. ESI-MS (M+1): 179 calc. for C6H4F2O2S.