[F:1][C:2]1[CH:3]=[C:4]([NH2:12])[C:5](=[CH:9][C:10]=1[F:11])[C:6]([OH:8])=[O:7].C(O)(=O)C.C(O[Cl:22])(C)(C)C>ClCCl.C(OCC)(=O)C>[Cl:22][C:3]1[C:2]([F:1])=[C:10]([F:11])[CH:9]=[C:5]([C:6]([OH:8])=[O:7])[C:4]=1[NH2:12]To a solution of 4,5-difluoroanthranilic acid (2.45 g, 14.2 mmol) in dichloromethane (25 mL) is added acetic acid (10 mL) and hypochlorous acid tert-butyl ester (1.75 mL, 15.6 mmol). After 2 hours, the reaction mixture is diluted with ethyl acetate and washed with water and brine. The organic layer is dried over MgSO4, filtered, and concentrated. The resulting residue is purified via flash column chromatography (5% isopropyl alcohol/1% formic acid/94% dichloromethane) to afford 3-chloro-4,5-difluoroanthranilic acid as an oil (2.97 g). MS CI: m/z 206 (M+).
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