Diethyl (ethoxymethylene)malonate → diethyl N-(3-oxo-1-cyclohexen-1-yl)-aminomethylenemalonate

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By the method described in Japanese Patent Application No. 24956/1978, diethyl N-(3-oxo-1-cyclohexen-1-yl)-aminomethylenemalonate was prepared from 3-amino-2-cyclohexenone and diethyl ethoxymethylenemalonate. The product was cyclized under heat to form ethyl 4-hydroxy-5-oxo-5,6,7,8-tetrahydroquinonine-3-carboxylate, followed by hydrolysis. The resulting ethyl 4-hydroxy-5-oxo-5,6,7,8-tetrahydroquinoline-3-carboxylate (2.35 g) was suspended in 80 ml of dimethylformamide. The suspension was heated to 60° C., and 1.52 g of potassium carbonate and 1.54 g of ethyl iodide were added, and the mixture was stirred at 70° C. for 30 minutes. Further, 3.46 g of ethyl iodide was added, and the mixture was stirred for 1 hour. The insoluble matter was removed by filtration, and the mother liquor was concentrated to dryness. The product was extracted with chloroform, and the chloroform was distilled off. Methylene chloride was added to the residue, and the insoluble matter was collected by filtration. There was obtained 2.4 g of the captioned product as a light yellow powder. The nuclear magnetic resonance spectrum (DMSO-d6, 60 MC, TMS) had signals at δ1.2-1.5 (6H, m), 1.8-3.3 (6H, m), 4.0-4.5 (4H, m), and 8.4 (1H, s).

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