Tetrahydrofuran → ethyl 1-(3-chloro-2-pyridinyl)-3-methyl-1H-pyrazole-5-carboxylate

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반응 단계

A mixture of 1.34 g of ethyl 2-methoxyimino-4-oxopentanoate, 1.23 g of 3-chloro-2-hydrazinopyridine, 25 ml of tetrahydrofuran and 50 ml of acetic acid was heated to reflux for 8 hours. The reaction mixture was concentrated under reduced pressure. Water was poured into the residue, and the mixture was extracted with methyl t-butyl ether two times. The combined organic layer was washed successively with a 1N aqueous sodium hydroxide solution, water and an aqueous saturated sodium chloride solution, dried over anhydrous magnesium sulfate, and concentrated under reduced pressure. The residue was subjected to silica gel column chromatography to obtain 0.30 g of ethyl 1-(3-chloro-2-pyridinyl)-3-methyl-1H-pyrazole-5-carboxylate of the formula:

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