Reaktion #82605

Reaktionsgleichung

6,7-dibromo-1,4-dihydro-2,3-quinoxalinedione

KNO3

→

5-nitro-6,7-dibromo-1,4-dihydro-2,3-quinoxalinedione

Ausbeute 76.0%

Lösungsmittel

H2SO4

Reaktionsbedingungen

Aufarbeitung

1. 1
   workup.WAITat room temperature for one day
2. 2
   Sonstigeresulting in the separation of a bright yellow precipitate, which
3. 3
   Filtrationwas collected by filtration
4. 4
   Waschenwashed with distilled water (2×2 mL)

Vorschrift

The procedure of Cheeseman, G. W. H., J. Chem. Soc. 1170 (1962) was adapted. To a stirred suspension of 6,7-dibromo-1,4-dihydro-2,3-quinoxalinedione (576 mg, 1.8 mMol) in concentrated H2SO4 (6 mL) at 0° C. for 30 min. was added KNO3 (220 mg, 2.18 mMol, Baker) in one portion. The mixture was stirred at 0° C. for 3 h then at room temperature for one day. The color of mixture was changed from red to yellow brown. Then it was poured into ice (60 g) resulting in the separation of a bright yellow precipitate, which was collected by filtration and washed with distilled water (2×2 mL) followed by ethanol (2×1 mL) to get 498 mg of crude 5-nitro-6,7-dibromo-1,4-dihydro-2,3-quinoxalinedione (76%, contains minor impurities by NMR). Crystallization from DMSO/H2O gave pure 5-nitro-6,7-dibromo-1,4-dihydro-2,3-quinoxalinedione as bright yellow microcrystals; mp: 352°-354° C. (dec.). IR (KBr, cm-1): 3387; 3256; 1756; 1700; 1537. NMR (1H, DMSO-d6): δ7.475 (s, 1H); 12.217 (s, 1H); 12.265 (s, 1H). HRMS: calcd for C8H3N3O4Br2 (M+) m/z: 362.8489; found: 362.8509.

Quelle