[Br:1][C:2]1[CH:3]=[C:4]([NH2:18])[C:5]([NH2:17])=[CH:6][C:7]=1[O:8][C:9]1[CH:14]=[CH:13][C:12]([F:15])=[CH:11][C:10]=1[F:16].[N:19]([O-])=O.[Na+]>C(O)(=O)C.C(OCC)(=O)C.O>[Br:1][C:2]1[C:7]([O:8][C:9]2[CH:14]=[CH:13][C:12]([F:15])=[CH:11][C:10]=2[F:16])=[CH:6][C:5]2[N:17]=[N:19][NH:18][C:4]=2[CH:3]=1A solution of 4-bromo-5-(2,4-difluorophenoxy)benzene-1,2-diamine (0.071 g, 0.22 mmol) in acetic acid (0.4 mL) was treated with water (1.1 mL) followed by sodium nitrite (0.078 g, 1.1 mmol) and stirred at 20° C. for 30 min. The reaction mixture was diluted with ethyl acetate and water. The organic layer was separated, washed with saturated sodium bicarbonate (2×) and brine, dried with magnesium sulfate, filtered, and concentrated to give a crude brown oil. Purification by flash column chromatography (100% hexanes to 60% EtOAc/hexanes) gave the desired product (57 mg, 78%) as a yellow solid. LCMS calculated for C12H7BrF2N3O (M+H)+: m/z=326.0, 328.0. found: 325.9, 327.9.
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