OXO-(2-OXO-TETRAHYDRO-FURAN-3-YL)-ACETIC ACID ETHYL ESTER → HCID 178470339, compound

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Reaction Steps

While stirring at room temperature, 8.12 g of synthetic zeolite A-4 powder were added to a solution of 8.12 g (97.70 mmol) of 3-aminopyrazole in 32 ml of acetic acid. Furthermore, a solution of 8.19 g (97.78 mmol) of ethyl (tetrahydro-2-oxo-3-furyl)glyoxylate obtained in Example 25 in 40 ml of acetic acid was added dropwise over 2 minutes while cooling with ice water and stirring, and the mixture was stirred for 4 hours at room temperature. Thereafter, insoluble matter was removed by filtration, and the filtrate was concentrated under reduced pressure. The residue was dissolved in 150 ml of chloroform, and the solution was poured into 700 ml of water. After full shake of the resultant mixture, the chloroform layer was separated, and the water layer was further extracted with chloroform (150 ml×2). After all the chloroform layers were put together and dried over anhydrous sodium sulfate, the solvent was distilled off. The residue was purified by column chromatography on silica gel (chloroform) to obtain 5.36 g of ethyl 6-(2-hydroxyethyl)pyrazolo[1,5-a]pyrimidin-7(4H)-one-5-carboxylate. To this product were added 7 ml (d=1.645, 75.10 mmol) of phosphorus oxychloride, and the mixture was stirred for 40 minutes in an oil bath heated to 100° C. under a nitrogen atmosphere. The reaction mixture was then cooled to about room temperature, and 7 ml (d=0.726, 50.32 mmol) of triethylamine was added to the reaction mixture. The resultant mixture was stirred for 30 minutes in the oil bath heated to 100° C. Thereafter, the reaction mixture was cooled with ice water, and 100 ml of chloroform were added thereto. The resultant mixture was poured into 600 ml of ice water and fully shaken. The chloroform layer was then separated, and the water layer was extracted with chloroform (100 ml×2). After all the chloroform layers were put together and dried over anhydrous magnesium sulfate, the solvent was distilled off. The residue was subjected to column chromatography on silica gel (chloroform) to obtain 3.60 g of ethyl 7-chloro-6-(2-chloroethyl)pyrazolo[1,5-a]pyrimidine-5-carboxylate. While cooling with ice water and stirring, 1.60 ml of 90% nitric acid and one drop of concentrated sulfuric acid were successively added to 14.2 ml of acetic anhydride, and the resultant mixture was then chilled to -10° C. While keeping this mixture at -5 to 0C., a solution of 3.60 g of ethyl 7-chloro-6-(2-chloro-ethyl)pyrazolo[1,5-a]pyrimidine-5-carboxylate in 4.30 ml of acetic anhydride was added dropwise thereto. After the resultant mixture was stirred for 20 minutes under the same conditions, it was poured into 300 ml of ice water, followed by extraction with 400 ml of ethyl acetate. After the resultant organic layer was washed twice with a saturated aqueous solution of sodium hydrogencarbonate and once with a saturated saline solution, and dried over anhydrous magnesium sulfate, the solvent was distilled off. The residue was subjected to column chromatography on silica gel (ethyl acetate:n-hexane=1:5, chloroform) to obtain 2.49 g (yield: 7.6%) of the intended product.

Provenance & Evidence