Acetic Anhydride → Methyl 1-acetyl-1H-indazole-5-carboxylate

関与物質

反応手順

To a stirred mixture of methyl 3-methyl-4-aminobenzoate (5.0 g, 30.0 mmol) and potassium acetate (2.94 g, 30.0 mmol) in chloroform (50 mL) is added acetic anhydride (5.66 mL, 60.0 mmol). The mixture is stirred for 30 min at rt, followed by the addition of 18-crown-6 (1.58 g, 6.0 mmol) and n-amyl nitrite (7.78 g, 66.0 mmol). The mixture is heated to reflux for 16 h, followed by cooling to rt. The mixture is washed sequentially with aqueous sodium bicarbonate solution (2×), water and brine. The organic layer is dried over MgSO4, filtered and concentrated in vacuo. The crude product is purified by flash chromatography on silica gel. Elution with hexanes-EtOAc (80:20) gives 3.1 g (47%) of methyl 1-acetyl-1H-indazole-5-carboxylate as a yellow solid: 1H NMR (400 MHz, CDCl3) δ 8.52-8.50, 8.3, 8.2, 4.0, 2.8.

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