Diethyl Oxalate → 6,7-Difluoroquinoxaline-2,3(1H,4H)-dione

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The title compound (Sarges, R. et al., J. Med. Chem. 33:2240 (1990)) was prepared using an adaptation of the method of Cheeseman. (Cheeseman, G. W. H. J. Chem. Soc. 1171 (1962)). A mixture of diethyl oxalate (1.11 g, 7.63 mmol and 4,5-difluoro-1,2-diaminobenzene (110 mg, 0.763 mmol) was heated to reflux under N2 for 2 h. The reaction was allowed to cool to room temperature and the solid collected by vacuum filtration and rinsed with hexanes and air dried. This ;gray brown solid was recrystallized from 20 ml of EtOH and the brown-white crystals collected by vacuum filtration and the crystals further dried under vacuum (0.5 torr, 25° C.) to yield 45.3 mg (30.0%) mp>360° C. (lit.>310° C.). 1H NMR (d6 -acetone) δ7.19 (t, 2H, ArH, JH-F =9.3), 10.9 (br s, 2H, NH).

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