[Mg].[C:2]([O:10][CH2:11][CH3:12])(=[O:9])[CH2:3][C:4]([O:6][CH2:7][CH3:8])=[O:5].[Br:13][C:14]1[CH:22]=[C:21]([F:23])[C:20]([F:24])=[CH:19][C:15]=1[C:16](Cl)=[O:17].S(=O)(=O)(O)O>C(O)C.CCOCC.C(Cl)(Cl)(Cl)Cl>[Br:13][C:14]1[CH:22]=[C:21]([F:23])[C:20]([F:24])=[CH:19][C:15]=1[C:16]([CH:3]([C:4]([O:6][CH2:7][CH3:8])=[O:5])[C:2]([O:10][CH2:11][CH3:12])=[O:9])=[O:17]Magnesium ribbon (7.3 g) is suspended in absolute ethanol (15 ml), and thereto is added carbon tetrachloride (1.5 ml), and thereto is added dropwise a mixture of diethyl malonate (48 g), absolute ethanol (30 ml) and anhydrous ether (120 ml) over a period of one hour. After the addition, the mixture is refluxed for 2 hours. After cooling till room temperature, a solution of 2-bromo-4,5-difluorobenzoyl chloride (92 g) in anhydrous ether (50 ml) is added dropwise to the mixture. After the addition, the mixture is allowed to stand overnight at room temperature. A mixture of ice-water (120 ml) and conc. sulfuric acid (8 ml) is added dropwise to the reaction mixture under ice-cooling. After the addition, the mixture is extracted with ether. The ether layer is washed with saturated aqueous sodium chloride solution and dried over magnesium sulfate. The solvent is distilled off under reduced pressure to give diethyl (2-bromo-4,5-difluorobenzoyl)malonate (123 g).
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