Potassium Nitrate → 5-Bromo-6-nitro-7-fluoro-1,4-dihydro-2,3-quinoxalinedione

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Reaction Conditions

Reaction Steps

The method of Cheeseman, supra. was adapted. 5-Bromo-7-fluoro-1,4-dihydroquinoxaline-2,3-dione (77 mg, 0.30 mMol) was dissolved in concentrated H2SO4 (1 mL) at 0° C. for 30 min, and KNO3 (35 mg, 0.346 mMol, Baker) was added to this solution. The mixture was stirred at 0° C. for 3 h and then at room temperature for 30 h. The mixture was poured into ice water (10 g) and the precipitate was collected by filtration. The precipitate was dissolved in 1N NaOH (10 mL), then was acidified to pH=2 with 4N HCl to give cream precipitate, which was collected by filtration, and was dried in the air at 50° C. for 4 h affording pure (by NMR) 5-bromo-6-nitro-7-fluoro-1,4-dihydro-2,3-quinoxalinedione (81 mg, 90%), as a white amorphous solid; mp: 320°-25° C. (dec. from 290° C.). IR (KBr, cm-1): 3416, 3071, 2952, 1721, 1609, 1546. NMR (1H, DMSO-d6): δ7.146 (d, J=10.2 Hz, 1H), 11.432 (s, 1H), 12.340 (s, 1H). HRMS: calcd. for C8H3N3O4BrF (M+) m/z: 302.9290, found: 302.9290.

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