General procedure for the synthesis of ethyl 3-oxo-3-(2,3,4,5-tetrafluorophenyl)propionate from monoethyl malonate potassium salt and tetrafluorobenzoyl chloride: monoethyl malonate potassium salt (3.66 g, 21.5 mmol), MgCl (2.44 g, 25.7 mmol) and triethylamine (TEA, 2.05 g, 20.3 mmol) were dissolved in acetonitrile (70 mL) in acetonitrile (70 mL) and the reaction was stirred for 2.5 h at 10-15 °C. Subsequently, a solution of 2,3,4,5-tetrafluorobenzoyl chloride (2.00 g, 10.3 mmol) in acetonitrile (10 mL) was slowly added dropwise at 0 °C for a controlled time of 15 min. After dropwise addition, TEA (0.23 g, 2.3 mmol) was added again. The reaction mixture was gradually warmed to room temperature and stirring was continued for 16 hours. After completion of the reaction, the volatiles were evaporated under reduced pressure. Toluene (30 mL) was added and evaporated again under reduced pressure. Subsequently, toluene (60 mL) was added and 1.5 M HCl (40 mL) was carefully added, controlling the reaction temperature to not exceed 25°C. The reaction was carried out under reduced pressure. The organic phase was washed sequentially with 1.5 M HCl (2 x 25 mL) and water (2 x 25 mL), dried with MgSO and finally concentrated under reduced pressure to give the target product ([M + 1] 265, 99% yield).
