Diazanaphthalenes compounds

The numbering for the quinoxaline ring system 1 proceeds clockwise from nitrogen an alternative name is 1,4-diazanaphthalene. Compound 2 is named accordingly as 3-methylquinoxaT in-2(I//)-one, and compound 3 as 2-chloroquinoxaline 4-oxide. 

Pyridazine (1,2-diazine) (1) and its benzo analogs cinnoline (1,2-diazanaphthalene) or benzo[c]pyridazine (2) and phthalazine (benzo[rf]pyridazine) (3) have been known since the nineteenth century. Although the basic synthetic principles and reactivity were investigated in the early years, interest in these compounds was not very intense, compared with pyrimidines and their bicyclic analogs, as they were not found in nature. However, during the last three decades intensive research has been stimulated because many derivatives have found application as a result of their biological activity. 

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