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24.g of magnesium turnings are suspended in 50 ml of anhydrous ethanol. 5 ml of carbon tetrachloride are added, and, when the reaction has started, a mixture of 160 g of diethyl malonate, 100 ml of absolute ethanol and 400 ml of anhydrous toluene is added dropwise at 50°-60° C. Thereafter, the mixture is heated to 50°-60° C. for a further hour, and cooled to -5° C. to -10° C. with dry ice acetone, and a solution of 212.5 g of 2,3,4,5-tetrafluorobenzoyl chloride (1) in 80 ml of absolute toluene is slowly added dropwise at this temperature. The mixture is stirred for 1 hour at 0° to -5° C., and is allowed to reach room temperature overnight, and a mixture of 400 ml of ice water and 25 ml of concentrated sulphuric acid is allowed to run in whilst cooling with ice. The phases are separated, and extraction with toluene is repeated twice. The combined toluene solutions are washed with saturated NaCl solution and dried with Na2SO4, and the solvent is stripped off in vacuo. 335 g of diethyl 2,3,4,5-tetra-fluorobenzoylmalonate (3) are obtained as a crude product.

1. additionis added dropwise at 50°-60° C
2. temperatureThereafter, the mixture is heated to 50°-60° C. for a further hour
3. waitto reach room temperature overnight
4. temperaturecooling with ice
5. customThe phases are separated
6. extractionextraction with toluene
7. washThe combined toluene solutions are washed with saturated NaCl solution
8. dry with materialdried with Na2SO4