Ammonium nitrate → 2,2,6,7-tetramethyl-5-nitro-1-benzofuran-3(2H)-one

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Reaction Steps

To a solution of 2,2,6,7-tetramethyl-1-benzofuran-3 (2H)-one obtained in Reference Example 41 (5.20 g, 27.3 mmol) in anhydrous trifluoroacetic acid (50 mL) and chloroform (5 mL) was added ammonium nitrate (2.10 g, 32.8 mmol) at 0° C., and the mixture was stirred at the same temperature for 2 hours, and then concentrated under reduced pressure. Water was added to the residue, which was extracted with ethyl acetate. The extract was washed with water and a saturated sodium hydrogen carbonate solution, and then was dried over anhydrous sodium sulfate. The solvent was distilled off under reduced pressure to obtain a residue, which was purified by silica gel column chromatography (hexane:ethyl acetate=50:1) to obtain 5.40 g (yield 84%) of the title compound. Melting point: 131-132° C. (ethyl acetate-hexane).

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