843-59-4

In a 250 mL four-neck flask equipped with a mechanical stirrer, thermometer, dropping funnel and condenser tube, 9.6 g (0.28 mol) of sodium hydride was suspended in 80 mL of ethylene glycol dimethyl ether. Subsequently, 25.6 g (0.1 mol) of diethyl 2,5-dioxocyclohexane-1,4-dicarboxylate was added successively to the suspension. At 60 °C, 86.8 g (0.46 mol) of 1,2-dibromoethane was slowly added dropwise. After the dropwise addition, the reaction temperature was raised to 90 °C and the reaction was continued with stirring for 20 h. Upon completion of the reaction, the unreacted 1,2-dibromoethane and the ethylene glycol dimethyl ether solvent were removed by distillation under reduced pressure. The residue was dissolved in a large amount of dichloromethane and the remaining solid was adjusted to weak acidity (pH ≈ 5-6) with concentrated hydrochloric acid. Subsequently, extraction with dichloromethane was carried out to combine the organic phases and remove the solvent. The crude product was purified by recrystallization from ethanol to afford diethyl 2,5-dioxobicyclo[2.2.2]octane-1,4-dicarboxylate in 95% purity and 50% yield.

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