[Cl:1][S:2]([OH:5])(=O)=[O:3].[F:6][C:7]([F:22])([F:21])[C:8]([N:10]1[CH2:13][CH:12]([C:14]2[CH:19]=[CH:18][CH:17]=[C:16]([F:20])[CH:15]=2)[CH2:11]1)=[O:9]>C(OCC)(=O)C>[F:20][C:16]1[CH:17]=[CH:18][C:19]([S:2]([Cl:1])(=[O:5])=[O:3])=[C:14]([CH:12]2[CH2:11][N:10]([C:8](=[O:9])[C:7]([F:6])([F:21])[F:22])[CH2:13]2)[CH:15]=1Chlorosulphonic acid (5 mL) was added to 2,2,2-trifluoro-1-[3-(3-fluorophenyl)azetidin-1-yl]ethanone (Intermediate 90, 1.15 g) with stirring and ice cooling. The mixture was stirred for 1 hour then poured carefully onto a mixture of ice and ethyl acetate. The organic layer was washed with water and concentrated in vacuo. The residue was purified by chromatography on silica, eluting with a mixture of ethyl acetate and cyclohexane with a gradient of 0-20% to give 4-fluoro-2-[1-(2,2,2-trifluoroacetyl)azetidin-3-yl]benzenesulfonyl chloride (0.910 g) as a white solid.
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