反应详情

A solution of ethyl 2,4-dioxohexanoate (˜0.345 mol), prepared as described in Part A of Example 10, in glacial acetic acid (350 mL) was cooled to 0° C. Ethylhydrazine oxalate (41.43 g, 0.276 mol) was added over a period of 20 minutes. The reaction was allowed to warm to ambient temperature, stirred for 20 hours, and concentrated under reduced pressure. The residue was adjusted to pH 10 with the addition of 2 M aqueous sodium carbonate, and chloroform was added. The mixture was filtered to remove a solid. The aqueous filtrate was extracted with chloroform (3×), and the combined organic fractions were dried over sodium sulfate, filtered, and concentrated under reduced pressure to provide 29.4 g of ethyl 1,5-diethyl-1H-pyrazole-3-carboxylate as an orange oil, which was used without purification.

1. concentrationconcentrated under reduced pressure
2. additionThe residue was adjusted to pH 10 with the addition of 2 M aqueous sodium carbonate, and chloroform
3. additionwas added
4. filtrationThe mixture was filtered
5. customto remove a solid
6. extractionThe aqueous filtrate was extracted with chloroform (3×)
7. dry with materialthe combined organic fractions were dried over sodium sulfate
8. filtrationfiltered
9. concentrationconcentrated under reduced pressure