Acetic Anhydride → 1-(5-Nitro-1H-indazol-1-yl)ethan-1-one

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Reaction Steps

Step 1) Dissolve commercially available 5-nitroindazole (100 g, 613 mmoles) in 2 L of THF and then add triethylamine (260 mL; 1.87 moles). Stir the solution at room temp until all the solid went into the solution, and then add acetic acid anhydride (94 g; 927 mmoles). After 2 h at room temperature, add 2 L of EtOAc and extract the mixture with 1 N HCl (2×800 mL). Wash the organic layer with aqueous sodium bicarbonate followed by saturated aqueous NaCl. Dry the organic layer with magnesium sulfate and concentrate to a thick slurry. Add t-Butyl methyl ether (300 mL) and filter the slurry. Collect the solid, rinse with t-butyl methyl ether, and dry under vacuum to afford 113 g (90%) of 1-(5-nitro-indazol-1-yl)-ethanone a pale yellow solid. 1H NMR (500 MHz, CDCl3) δ 8.70 (d, 1H, J=2.0 Hz), 8.58 (d, 1H, J=9.5 Hz), 8.44 (dd, 1H J=7.0, 2.0 Hz), 8.31 (s, 1H), 2.84 (s, 1H).

Provenance & Evidence