Acetic Anhydride → ethyl 1-acetyl-7-(acetyloxy)-3-ethyl-1H-indazole-5-carboxylate

Participants

Reaction Steps

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).

Provenance & Evidence