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温度

0 °C

To a solution of 7-chloro-5-trifluoromethyl-1,4-dihydro-2,3-quinoxalinedione (29 mg, 0.16 mmol) in concentrated H2SO4 (0.5 mL) at 0° C. was added KNO3 (11.6 mg, 0.115 mmol). The mixture was stirred at 0° C. for 0.5 h, then at room temperature for 12 h and it was poured into ice water (2 g). The precipitate was collected by filtration, affording 31 mg (91.4%) of crude title compound. It was dissolved in 1N KOH (1 mL) and filtered. The filtrate was acidified to pH=2 with 4N HCl to give a yellow precipitate, which was collected by filtration, and dried at 50° C. for 4 h, affording the title compound (23 mg, 67%) as a yellow powder. Recrystallization from DMSO/H2O gave pure title compound as yellow microcrystals. Mp: 278°-80° C., IR (KBr, cm-1): 3425, 3150, 3125, 1712, 1618, 1556; 1H NMR (DMSO-d6): δ7.531 (s, 1H), 11.803 (s, 1H), 12.459 (s, 1H). HRMS: calcd. for C9H3ClF3N3O4 (M+) m/z: 308.9763, found: 308.9759.

1. waitat room temperature for 12 h
2. filtrationThe precipitate was collected by filtration
3. customaffording 31 mg (91.4%) of crude title compound
4. filtrationfiltered
5. customto give a yellow precipitate, which
6. filtrationwas collected by filtration
7. customdried at 50° C. for 4 h