[Br:1][C:2]1[CH:3]=[C:4]([F:11])[C:5]([F:10])=[C:6]([CH:9]=1)[CH:7]=O.Cl.[CH3:13][O:14][NH2:15].C([O-])([O-])=O.[K+].[K+]>COCCOC>[CH3:13][O:14]/[N:15]=[CH:7]/[C:6]1[CH:9]=[C:2]([Br:1])[CH:3]=[C:4]([F:11])[C:5]=1[F:10]A mixture of 5-bromo-2,3-difluorobenzaldehyde (17.38 g, 78.6 mmol), O-methylhydroxylamine hydrochloride (7.23 g, 86.46 mmol), and K2CO3 (13 g, 94.32 mmol) in DME (80 mL) was heated at 40° C. for 14 h. Work-up: the reaction mixture was filtered. The filtrate was concentrated in vacuo, and the residue was purified by column chromatography on silica gel (0˜2% EtOAc in petroleum ether), to give (E)-5-bromo-2,3-difluorobenzaldehyde O-methyl oxime (19.65 g). 1H NMR (CDCl3, 300 MHz): δ 8.20 (s, 1H), 7.76-7.73 (m, 1H), 7.35-7.29 (m, 1H), 4.01 (s, 3H).
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