Nuclear Halogenoquinoxalines by Direct Halogenation

6-Chloro-5-nitro-2,3(l, 477)-quinoxalinedione (31, R = H) gave 6-bromo-7-chloro-8-nitro-2,3(l//,477)-quinoxalinedione (31, R = Br) (NBS, Me2NCHO, 

6-Methoxy-5,8-quinoxalinequinone (34) gave 6-bromo-7-methoxy-5,8-quinox-alinequinone (35) (Br2, AcOH-AcONa, 20°C, 12h 58%) the same product (35) was also obtained from 5,8-diacetoxy-6-methoxyquinoxaline (36) (excess Br2, AcOH-AcONa, 20°C, 5 days 31% an oxidation step was clearly involved in this procedure).  

8-Dimethoxyquinoxalme (37) gave 6,7-dichloro-5,8-quinoxalinequinone (38) (lOM HCl, 20°C, NaClOs J, during 30 min 2%, clearly involving hydro- 

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