[N:1]([O-])=O.[Na+].[Br:5][C:6]1[CH:7]=[C:8]([CH:10]=[CH:11][C:12]=1[F:13])[NH2:9].O.O.[Cl:16][Sn]Cl>Cl>[ClH:16].[Br:5][C:6]1[CH:7]=[C:8]([NH:9][NH2:1])[CH:10]=[CH:11][C:12]=1[F:13]A solution of sodium nitrite (4.2 g, 60 mmol) was added drop-wise to a mixture of 3-bromo-4-fluoroaniline (11.2 g, 58.9 mmol) and concentrated HCl (30 mL, 0.36 M) at 0° C. over 30 min. The resulting clear solution was stirred for 45 min, and a solution of SnCl2.2H2O (27 g, 120 mmol) in concentrated HCl (30 mL) was added drop-wise at 0° C. over 1.5 h. The mixture was stirred for 18 h at room temperature. The resulting precipitate was collected by filtration and crystallized from ethanol to provide the title compound (6.2 g, 42%) as a yellow powder: 1H NMR (300 MHz, DMSO-d6) δ 10.24 (s, 3H), 8.42 (s, 1H), 7.36-7.30 (m, 2H), 7.03-6.98 (m, 1H).
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