Nuclear Halogenoquinoxalines from Miscellaneous Substrates

7-Dichloro-2-methyl-3-phenylsulfonylquinoxaline 1,4-dioxide (55, R = S02Ph) gave 2-bromo-6,7-dichloro-3-methylquinoxaline 1,4-dioxide (55, R = Br) (48% HBr, 80°C, 30 min then 20°C, 12 h 31%) 2-methyl-3-phenylsulfonylquinoxaline 1,4-dioxide gave 2-chloro-3-methylquinoxaline 1,4-dioxide (35% HCl, 70°C, 15 min 87% several analogs likewise).  

6-Nitroquinoxaline 4-oxide (57) gave 2-chloro-7-nitroquinoxaline (58) (neat POCI3, reflux, 90 min 82%) in contrast, 6-nitroquinoxaline 1-oxide (59) gave a separable 5 4 1 mixture of 6-chloro-7-nitro- (60), 5-chloro-6-nitro-(61), and 2-chloro-6-nitroquinoxaline (62) [neat POCI3, reflux, 18 h 86% (mixture) from which the individual products were isolated in unstated yields]. 

2-Azido-6-chloroquinoxaline 4-oxide (63) gave 2-azido-3,6-dichloroquinoxaline (64) (neat POCI3, reflux, 1 h 93%). ° 

7-Dinitroquinoxaline (52) gave a separable mixture of 6-chloro-7-nitro- (53) and 6,7-dichloroquinoxaline (54) [4M HC1 (gas) in Me2NCHO, 85°C, 12 h 51% and 18%, respectively) under more vigorous conditions, the same substrate (52) gave only 6,7-dichloroquinoxaline (54) (substrate, Me2NCHO, 85°C HC1 gas I, exothermic rise to 110°C, 7 h 75%).368 

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