[Br:1][C:2]1[C:9]([F:10])=[CH:8][C:5]([CH:6]=O)=[C:4]([F:11])[CH:3]=1.Cl.[OH:13][NH2:14]>N1C=CC=CC=1.C(O)C.[Cl-].[NH4+]>[Br:1][C:2]1[C:9]([F:10])=[CH:8][C:5](/[CH:6]=[N:14]/[OH:13])=[C:4]([F:11])[CH:3]=1A solution of 4-bromo-2,5-difluorobenzaldehyde (7.0 g, 31.67 mmol), hydroxyl amine hydrochloride (2.42 g, 34.84 mmol) in pyridine (35 mL) and ethanol (35 mL) was stirred at room temperature for 30 min. The reaction mixture was diluted with saturated ammonium chloride solution and extracted with ethyl acetate. The organic phase was washed with saturated brine solution, dried (Na2SO4), filtered, and concentrated under reduced pressure. The crude product was purified by flash chromatography (SiO2, eluting with 5-100% ethyl acetate in hexanes) to provide the title compound as a yellow solid (4.0 g, 53%): ESIMS m/z 238 [(M+2H)+].
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