A mixture of pinacolone (740 mmol) and diethyl oxalate (820 mmol) was added dropwise to a solution of sodium ethoxide (prepared by dissolving 740 mmol of sodium in 450 mL of ethanol) at room temperature, followed by stirring the reaction for 1 hour at 78 °C. Upon completion of the reaction, the reaction mixture was cooled to room temperature and slowly poured into a pre-cooled aqueous 5 M hydrochloric acid solution (800 mL). Extraction was carried out with methyl tert-butyl ether (300 mL each time, 3 times in total), and the combined organic phases were washed with saturated aqueous sodium chloride solution (500 mL) and dried over anhydrous sodium sulfate. After filtration, the solvent was removed by distillation under reduced pressure to afford the target product ethyl 5,5-dimethyl-2,4-dioxohexanoate as a red liquid. Product weight: 140 g, yield: 93.3%. Mass spectrum (ES+): m/z 199 ([M+H]+). Nuclear magnetic resonance hydrogen spectrum (1H NMR, CDCl3): δ 6.5 (1H, s, CH), 4.3 (2H, q, OCH2), 1.35 (3H, t, CH3), 1.15 (9H, s, 3×CH3).
