反应详情

4,5-difluoro-2-nitroaniline (2.17 g, 12.5 mmol) was dissolved in 55 ml of ethanol and 250 mg of 10% palladium on carbon was added. The mixture was hydrogenated until the theoretical amount of hydrogen had been absorbed, using a low pressure hydrogenation apparatus. The catalyst was filtered off and the filtrate, containing 4,5-difluoro-o-phenylenediamine, was kept under a nitrogen atmosphere at 0° C. followed by addition of a solution of glyoxylic acid hydrate (1.28 g, 13.7 mmol) in water (3 ml). When the addition was complete the reaction temperature was allowed to reach room temperature during 2 h and 30 ml of water was added. The precipitate was filtered off and dissolved in 60 ml of 5% NaOH solution at 50° C. followed by addition of activated carbon. The mixture was filtered and the filtrate was acidified (pH=1) by addition of concentrated hydrochloric acid. The pinky precipitate was filtered off, washed with water and dried to afford 1.25 g (55 %) of 6,7-difluoroquinoxalin-2(1H)-one melting at 284°-85° C. 1H-NMR (DMSO-d6): 7.27 (m, 1H), 7.95 (m, 1H), 8.20 (s, 1H), 12.55 (s,1H).

1. customhad been absorbed
2. filtrationThe catalyst was filtered off
3. additionthe filtrate, containing 4,5-difluoro-o-phenylenediamine
4. customwas kept under a nitrogen atmosphere at 0° C.
5. additionWhen the addition
6. filtrationThe precipitate was filtered off
7. dissolutiondissolved in 60 ml of 5% NaOH solution at 50° C.
8. additionfollowed by addition of activated carbon
9. filtrationThe mixture was filtered
10. additionby addition of concentrated hydrochloric acid
11. filtrationThe pinky precipitate was filtered off
12. washwashed with water
13. customdried