Potassium Nitrate → 6-Bromo-7-chloro-5-nitro-1,4-dihydro-2,3-quinoxalinedione

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Reaction Steps

To a stirred solution of 6-bromo-7-chloro-5-nitroquinoxaline-2(1H)-one (0.025 g, 0.082 mmol, as prepared above) in conc. H2SO4 (0.5 mL) was added KNO3 (0.011 g, 0.11 mmol) and the resulting dark red solution was stirred at room temperature for 65 h. The solution was then cooled in an ice-bath and diluted with ice to a total volume of 5.0 mL. The precipitated solid was filtered, washed with water (2.0 mL) and dried under vacuum to obtain 0.019 g (72%) crude product. It was purified as follows. 0.016 g crude product was taken up in 1N NaOH (1.1 mL). The insoluble solid was centrifuged and the supernatant liquid was acidified with conc. HCl to pH ~2. The precipitated solid was filtered, washed with water (1.0 mL), and dried under vacuum to furnish 0.010 g (38%) pure (purity by HPLC>97%) title compound as a cream colored powder; m.p. 338°-343° C. (decomposed); 1H NMR (DMSO-d6): δ7.351 (s, 1H), 12.251 (s overlapped by a br s, 2H); Elemental analysis for C8H3BrClN3O4, calcd: C, 29.98%; H, 0.94%; N, 13.11%, found: C, 29.79; H, 0.77; N, 12.71.

Provenance & Evidence