反应详情

5-Chloro-7-fluoro-1,4-dihydro-2,3-quinoxalinedione was prepared using an adaptation of the method of Cheeseman. (Cheeseman, G. W. H. J. Chem. Soc. 1171 (1962)). A mixture of diethyl oxalate (2.64 g, 18.1 mmol) and 1,2-diamino-3-chloro-5-fluorobenzene (290 mg, 1.81 mmol) was heated to reflux under N2 for 10 h. The reaction was allowed to cool to room temperature and the shiny yellow-brown crystals collected by vacuum filtration and rinsed with EtOH (10 mL) and air dried to give 164.1 mg (42%). A portion of this solid was taken and dissolved in 10 mL 1N NaOH. The solution was treated with activated charcoal and filtered through a pad of Celite. The resulting solution was carefully acidified with 1N HCl (pH=6). Pale yellow needles slowly formed in the solution and were collected by vacuum filtration, rinsed with 20 mL of H2O and further dried under vacuum (0.1 torr, 78° C.) to yield 67.8 of powdery pale yellow crystals. mp 306°-308° C. (dec), 1H NMR (d6 -DMSO) δ7.28 (s, 1H, ArH), 7.56 (s, 1H, ArH), 11.7 (br s, 2H, NH), EIMS m/z 216 (M+2,34, 214 (M+, bp), 188 (21), 186 (68), 123 (61), 131 (62). EIHRMS calc. for C8H4ClFN2O2 213.9945, found 213.9961.

1. temperaturewas heated
2. temperatureto reflux under N2 for 10 h
3. filtrationthe shiny yellow-brown crystals collected by vacuum filtration
4. washrinsed with EtOH (10 mL) and air
5. customdried
6. customto give 164.1 mg (42%)
7. filtrationfiltered through a pad of Celite
8. customPale yellow needles slowly formed in the solution
9. filtrationwere collected by vacuum filtration
10. washrinsed with 20 mL of H2O
11. customfurther dried under vacuum (0.1 torr, 78° C.)