Ethyl 2-oxocyclopentanecarboxylate → HCID 136203297、化合物

A 250-mL round bottomed flask was charged with cyclopentanecarboximidamide hydrochloride (5.38 g, 36.2 mmol), ethyl 2-oxocyclopentanecarboxylate (5.14 g, 38.7 mmol), and ethanol (100 mL). To the stirred mixture at rt was added sodium methoxide (3.91 g, 72.4 mmol). The resulting mixture was stirred under reflux for 22 h. After cooling to room temperature, the mixture was evaporated under reduced pressure to 25 mL. The residual slurry was cautiously treated with 2N HCl (50 mL). The solution was extracted with ethyl acetate (4×50 mL). The combined extract was washed with saturated sodium chloride (2×25 mL), dried over sodium sulfate, filtered, and concentrated under reduced pressure to afford the title compound which was carried forward into the next step without further purification.