[F:1][C:2]1[C:7]([C:8]([OH:10])=[O:9])=[C:6]([CH3:11])[C:5]([N+:12]([O-:14])=[O:13])=[CH:4][CH:3]=1.OS(O)(=O)=O.[Br:20]N1C(C)(C)C(=O)N(Br)C1=O>O>[Br:20][C:3]1[C:2]([F:1])=[C:7]([C:6]([CH3:11])=[C:5]([N+:12]([O-:14])=[O:13])[CH:4]=1)[C:8]([OH:10])=[O:9]To a solution of 6-fluoro-2-methyl-3-nitrobenzoic acid (100 mg, 0.5 mmol) in concentrated H2SO4 (0.5 ml, 9.38 mmol) was added 1,3-dibromo-5,5-dimethylimidazolidine-2,4-dione (79 mg, 0.28 mmol) at room temperature and under nitrogen. The reaction mixture was stirred for 6 hours during which time a precipitate formed. The reaction mixture was added slowly to deionized water (3 ml) and the resulting precipitate was filtered. The solid was washed with deionized water (2 ml) and air dried for 2 hours to give 123 mg (88%) of 3-bromo-2-fluoro-6-methyl-5-nitrobenzoic acid as a pale yellow solid. LC-MS 94%, 1.61 min (3 minute LC-MS method), m/z=275.9/277.9 (ES−), 1H NMR (500 MHz, Chloroform-d) δ ppm 8.25 (d, J=6.2 Hz, 1H), 2.58 (s, 3H).
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