Reaktion #81984

Reaktionsgleichung

diethyl oxalate

3-bromo-4,5-difluoro-1,2-diaminobenzene

charcoal

→

title compound

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

Lösungsmittel

NaOH

Reaktionsbedingungen

Aufarbeitung

1. 1
   Temperaturwas heated
2. 2
   Temperaturto reflux under N2 for 15 h
3. 3
   Filtrationthe dark-brown solid collected by vacuum filtration
4. 4
   Waschenrinsed with EtOH (20 mL) and air
5. 5
   Sonstigedried
6. 6
   Sonstigeto give 215 mg (42%)
7. 7
   Temperaturwith heating
8. 8
   Filtrationfiltered through a pad of Celite
9. 9
   SonstigePale yellow needles slowly formed in the solution
10. 10
    Filtrationwere collected by vacuum filtration
11. 11
    Waschenrinsed with 20 mL of H2O
12. 12
    Sonstigedried under vacuum (0.1 torr, 78° C.)

Vorschrift

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.

Quelle