Oxalic acid dihydrate → 6-Chloro-7-trifluoromethyl-1,4-dihydro-2,3-quinoxalinedione

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A mixture of 3,4-diamino-6-chlorobenzotrifluoride (185 mg, 0.88 mmol) and oxalic acid dihydrate (117 mg, 0.93 mmol, used as received) in 2N HCl (4 mL) was refluxed at 170°-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 twice by cold water (2×2 mL), collected by filtration, and dried at 60° C. with reduced pressure for 2 h, affording 180 mg of crude title compound (77.3% ) as a light yellow powder. The crude product was dissolved in 1N NaOH (6 mL) and filtered. The filtrate was acidified to pH=6, affording 138 mg of title compound. It was recrystallized from DMSO/H2O twice to give 102 mg of pure compound (43.9%) as yellow microcrystals. mp: >360° C. (dec. from 295° C.). IR (KBr, cm-1) 3425, 3200, 1731, 1706, 1625; 1400. 1H NMR (DMSO-d6): δ 7.274 (s, 1H); 7.478 (s, 1H); 12.145 (s, 2H). HRMS: calcd for C9H4ClF3N2O2 (M+) m/z: 263.9912; found: 263.9919.

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