Oxalic acid dihydrate → 2,3-Quinoxalinedione, 1,4-dihydro-5,7-bis(trifluoromethyl)-

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A mixture of 1,2-diamino-3,5-bis(trifluoromethyl)aniline (94 mg, 0.38 mmol) and oxalic acid dihydrate (53 mg, 0.42 mmol, used as received) in 4N HCl (2 mL) was refluxed at 120°-5° C. for 3 h, then cooled to room temperature. The mixture was centrifuged and the liquid layer was removed. The yellow solid was washed by cold water (2×2 mL), collected by filtration, and dried at 60° C. under reduced pressure for 2 h, affording 45 mg of crude 5,7-bis(trifluoromethyl)-1,4-dihydro-2,3-quinoxalinedione (40% ) as a yellow powder. The crude compound was dissolved in 1N NaOH (6 mL) and filtered. The filtrate was acidified to pH=5, affording 23 mg of pure 5,7-bis(trifluoromethyl)-1,4-dihydro-2,3-quinoxalinedione. Mp: 305°-8° C. (dec. from 295° C.). IR (KBr, cm-1) 3421, 3235, 1749, 1690, 1631. 1H NMR (DMSO-d6): δ 7.654 (s, 1H); 7.687 (s, 1H); 11.584 (s, 1H); 12.311 (s, 1H). HRMS: calcd for C10F6H4N2O2 (M+) m/z: 298.0176; found: 298.0170.

Provenance & Evidence