21080-80-8

Sodium ethanolate solution was prepared by dissolving sodium metal (16.19 g) in anhydrous ethanol (150 ml) at room temperature and under nitrogen protection. After cooling the reaction mixture to 0°C, a mixture of diethyl oxalate (34.76 g) and cyclopropylmethyl ketone (20 g) was slowly added dropwise for about 15 min. After the dropwise addition was completed, the reaction mixture was allowed to warm up to room temperature naturally. Subsequently, anhydrous ethanol (100 ml) was added and stirring was continued for 1 hour at room temperature. The reaction mixture was heated to 80 °C, maintained for 45 minutes and then cooled to room temperature and subsequently concentrated under reduced pressure. Ethyl acetate was added to the resulting solid, washed with ethanol and filtered through a Brinell funnel to give a fine powdery solid. The solid was dissolved in water and acidified by adjusting the pH to 2 with dilute sulfuric acid. The acidified solution was extracted with ether, the organic phase was dried with anhydrous sodium sulfate and concentrated under reduced pressure to obtain the target compound ethyl 4-cyclopropyl-2,4-oxobutanoate in brown liquid form (40 g, 93% yield).

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