Nuclear Halogenoquinoxalines from Quinoxalinones

This transformation is usually done with neat phosphoryl chloride, but a variety of other reagents may be used, as illustrated in the following classified examples. 

Quinoxalines Supplement II, Chemistry of Heterocyclic Compounds, Volume 61, by Desmond J. Brown ISBN 0-471-26495-4 Copyright 2004 John Wiley Sons, Inc. 

6-Chloro-2(lf/)-quinoxalinone gave 2,6-dichloroquinoxaline (3, R = H) (POCI3, reflux, 90 min 83%) 6-chloro-2,3(l//,4//)-quinoxahnedione gave 2,3,6-trichloroquinoxaline (3, R = C1) (POCI3, reflux, 16 h 74% also analogs 

7-Dimethoxy-3-phenyl-2(l/7)-quinoxalinone gave 2-chloro-5,7-dimethoxy-3-phenylquinoxaline (4) (POCI3, reflux, 30 min 94%) 6,7-dimethoxy-2,3(1//,4//)-quinoxalinedione gave 2,3-dichloro-6,7-dimethoxyquinoxaline (5) (POCI3, 100°C, 4h 83%)J  

6-Chloro-l-methyl-2,3( 1 //,4//)-quinoxalinedione (6) gave 3,6-dichloro-l-methyl-2(l//)-quinoxalinone (7) (POCI3, reflux, 90 min 74% note immunity of the nontautomeric oxo substituent to chlorolysis under these conditions) 418 

---