Oxalic acid dihydrate → 7-Bromo-5-trifluoromethyl-1,4-dihydro-2,3-quinoxalinedione

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Reaction Steps

A mixture of 2,3-diamino-5-bromobenzotrifluoride (150 mg, 0.612 mmol) and oxalic acid dihydrate (81 mg, 0.643 mmol, used as received) in 2N HCl (4 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 twice by cold water (2×2 mL), collected by filtration, and dried at 60° C. for 2 h, affording 150 mg of crude title compound (81.9%) as a red powder. The crude compound was dissolved in 1N NaOH (6 mL) and filtered. The filtrate was acidified to pH=6, affording 135 mg of title compound. Recrystallization from DMSO/H2O gave 125 mg of pure title compound (68.3%) as red microcrystals. Mp: 307°-9° C. (dec. from 290° C.). IR (KBr, cm-1) 3412, 3250, 1756, 1706, 1606; 1H NMR (DMSO-d6): δ 7.514 (d, 1H, J=1.5 Hz); 7.556 (d, 1H, J=1.5 Hz); 11.342 (s, 1H); 12.220 (s, 1H). HRMS: calcd for C9H4BrF3N2O2 (M+) m/z: 307.9407; found: 307.9420.

Provenance & Evidence