反应详情

A solution of crude ethyl 2-[(3-ethyl-1H-pyrazol-4-yl)methylene]-4-oxopentanoate (4 g, 15.8 mmol) in acetic anhydride (10 mL), sodium acetate (2.6 g, 32 mmol) was added at room temperature and the mixture was heated at reflux for 4 h. The reaction mixture was cooled to room temperature, basified (pH ˜9) using aqueous NaHCO3 solution and extracted with ethyl acetate (2×50 mL). The combined organic layers were washed with water (25 mL), saturated aqueous NaCl (25 mL), dried over anhydrous Na2SO4 and concentrated to obtain the crude product; which was purified by column chromatography (60-120 mesh silica gel) using 2-3% ethyl acetate in pet-ether as eluents to afford ethyl 1-acetyl-7-(acetyloxy)-3-ethyl-1H-indazole-5-carboxylate (1.7 g, 34%) as brown solid. 1H NMR (CDCl3) δ 8.44 (s, 1H), 8.24 (s, 1H), 4.58 (q, 2H), 3.2 (s, 3H), 2.9 (s, 3H), 2.58 (s, 3H), 1.6 (t, 3H).

1. temperaturethe mixture was heated
2. temperatureat reflux for 4 h
3. extractionextracted with ethyl acetate (2×50 mL)
4. washThe combined organic layers were washed with water (25 mL), saturated aqueous NaCl (25 mL)
5. dry with materialdried over anhydrous Na2SO4
6. concentrationconcentrated
7. customto obtain the crude product
8. customwhich was purified by column chromatography (60-120 mesh silica gel)