Methane → 5-Bromo-6,7-difluoro-1,4-dihydro-2,3-quinoxalinedione

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Reaction Steps

The title compound was prepared using an adaptation of the method of Cheeseman. (Cheeseman, G. W. H. J. Chem. Soc. 1171 (1962)). A mixture of diethyl oxalate (2.70 g, 18.5 mmol) and 3-bromo-4,5-difluoro-1,2-diaminobenzene (410 mg, 1.85 mmol) was heated to reflux under N2 for 15 h. The reaction was allowed to cool to room temperature and the dark-brown solid collected by vacuum filtration and rinsed with EtOH (20 mL) and air dried to give 215 mg (42%). A portion of this solid (150 mg) was taken and dissolved in 20 mL 1N NaOH with heating. The solution was treated with activated charcoal and filtered through a pad of Celite. The resulting solution was carefully acidified with 1N HCl (pH=1). Pale yellow needles slowly formed in the solution and were collected by vacuum filtration, rinsed with 20 mL of H2O and dried under vacuum (0.1 torr, 78° C.) to yield 67.8 mg of powdery pale yellow crystals, mp 306°-310° C. (dec). 1H NMR (d6 -DMSO) δ 7.09 (dd, 1H, J=7.5, H-8), 11.3 (br s, 1H, NH), 12.1 (br s, 1H, NH). EIMS m/z 278 (M+2, 75), 276 (M+, 77), 250 (56), 248 (57), 14 1 (bp). EIHRMS calc. for C8H4BrF2N2O2 275.9346, found 275.9331.

Provenance & Evidence