[Mg].[C:2]([O:8][CH2:9][CH3:10])(=[O:7])[CH2:3][C:4]([O-:6])=[O:5].[CH3:11][C:12](C)=O.C(=O)=O.[Cl:18][C:19]1[C:27]([F:28])=[C:26]([Cl:29])[CH:25]=[C:24]([F:30])[C:20]=1[C:21](Cl)=[O:22].S(=O)(=O)(O)O>C(O)C.C1(C)C=CC=CC=1.C(Cl)(Cl)(Cl)Cl>[Cl:18][C:19]1[C:27]([F:28])=[C:26]([Cl:29])[CH:25]=[C:24]([F:30])[C:20]=1[C:21]([CH:3]([C:4]([O:6][CH2:11][CH3:12])=[O:5])[C:2]([O:8][CH2:9][CH3:10])=[O:7])=[O:22]2.1 g of magnesium filings are suspended in 5 ml of anhydrous ethanol. 0.5 ml of carbon tetrachloride is added and, when the reaction has started, a mixture of 14 g of ethyl malonate, 10 ml of absolute ethanol and 41 ml of toluene is added dropwise. The mixture is then heated at 70° C. for a further 1.5 hours and cooled to -5° C. to -10° C. with acetone/dry ice, and a solution of 21.5 g of 2,4-dichloro-3,6-difluorobenzoyl chloride in 30 ml of toluene is slowly added dropwise at this temperature. The mixture is stirred at 0° C. for 1 hour and allowed to come to room-temperature overnight, and a mixture of 35 ml of ice-water and 5 ml of concentrated sulphuric acid is allowed to run in, while cooling with ice. The phases are separated and subsequent extraction is carried out twice with toluene. The combined toluene solutions are washed once with saturated sodium chloride solution and dried with Na2SO4 and the solvent is stripped off in vacuo. 34.7 g of diethyl (2,4-dichloro-3,6-difluorobenzoyl)-malonate are obtained as a crude product.
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