C(O)=[O:2].[F:4][C:5]1[CH:6]=[C:7]([CH:13]([CH3:18])[C:14]([O:16][CH3:17])=[O:15])[CH:8]=[CH:9][C:10]=1[S:11][CH3:12].OO.C(OCC)(=O)C.CCCCCC.[OH2:33]>>[F:4][C:5]1[CH:6]=[C:7]([CH:13]([CH3:18])[C:14]([O:16][CH3:17])=[O:15])[CH:8]=[CH:9][C:10]=1[S:11]([CH3:12])(=[O:2])=[O:33]Formic acid (6.5 mL, 1 eq) was added to methyl 2-(3-fluoro-4-(methylthio)phenyl)propanoate (1 g, crude) and the mixture cooled to 0° C. Hydrogen peroxide (1.4 mL, 3 eq) was added drop wise at 0° C. and the reaction mixture was stirred overnight at room temperature. Progress of the reaction was monitored by TLC (20% ethyl acetate/hexane, Rf˜0.4). On completion of the reaction, the contents were cooled to 0° C., water was added and the mixture was extracted with ethyl acetate (2×25 mL). The combined extract was washed with NaHCO3 solution, dried over sodium sulfate and concentrated under reduced pressure to yield methyl 2-(3-fluoro-4-(methylsulfonyl)phenyl)propanoate as colorless thick liquid (1 g, crude). The crude product obtained was directly used for the next step.
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