Diazanaphthalenes oxidation

AO is also effective in metabolizing a wide range of nitrogen-containing heterocycles such as purines, pyrimidines, pteridines, quinolines, and diazanaphthalenes (95). For example, phthalazine is rapidly converted to 1-phthalazinone by AO and the prodrug, 5-ethynyl-2-(l//)-pyrimidone, is oxidized to the dihydropyrimidine dehydrogenase mechanism-based inhibitor, 5-ethynyluracil, by AO (Fig. 4.40) (96). 

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. 

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