Br.[F:2][C:3]1[C:8]([O:9]C)=[C:7]([CH:11]=[O:12])[CH:6]=[CH:5][C:4]=1[C:13]1[CH:18]=[CH:17][C:16]([F:19])=[CH:15][C:14]=1[F:20]>C(O)(=O)C>[F:2][C:3]1[C:8]([OH:9])=[C:7]([CH:11]=[O:12])[CH:6]=[CH:5][C:4]=1[C:13]1[CH:18]=[CH:17][C:16]([F:19])=[CH:15][C:14]=1[F:20]48% hydrobromic acid (22.0 mL) was added at room temperature to an acetic acid (120 mL) solution of 2,2′,4′-trifluoro-3-methoxybiphenyl-4-carbaldehyde (5.14 g), and the mixture was stirred at 120° C. for 16 hours in a nitrogen atmosphere. The reaction mixture was cooled to room temperature, and then, the solvent was distilled off under reduced pressure. The obtained residue was neutralized with a 1 M aqueous sodium hydroxide solution, followed by extraction with ethyl acetate. The obtained organic layer was washed with water and saturated saline in this order and dried over anhydrous magnesium sulfate, and then, the solvent was distilled off under reduced pressure. The obtained residue was passed through a short silica gel column (hexane/ethyl acetate) to obtain the title compound (4.60 g).
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