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0 °C

24.3 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 up, a mixture of 160 g of diethyl malonate, 100 ml of absolute ethanol and 400 ml of anhydrous ether is added dropwise, vigorous reflux being observed. After the reaction has moderated, the mixture is heated to boiling for 2 hours, then cooled down to -5° C. to -10° C. with dry ice/acetone and, at this temperature, a solution of 227.5 g of 2,4-dichloro-5-fluorobenzoyl chloride (1) in 100 ml of absolute ether is slowly added dropwise. The mixture is stirred at 0° C. for 1 hour, allowed to reach room temperature overnight and, while cooling in ice, a mixture of 400 ml of ice-water and 25 ml of concentrated sulphuric acid is allowed to run in. The phases are separated and the aqueous phase is extracted twice more with ether. The combined ether solutions are washed with saturated NaCl solution, dried with Na2SO4 and the solvent is removed in vacuo. 349.5 g of diethyl 2,4-dichloro-5-fluorobenzoylmalonate (3) are obtained as a crude product.

1. additionis added dropwise
2. temperaturevigorous reflux
3. temperaturethe mixture is heated
4. waitto reach room temperature overnight
5. temperaturewhile cooling in ice
6. customThe phases are separated
7. extractionthe aqueous phase is extracted twice more with ether
8. washThe combined ether solutions are washed with saturated NaCl solution
9. dry with materialdried with Na2SO4
10. customthe solvent is removed in vacuo