2- quin oxaline derivatives

Following extraction/cleanup, quinoxaline-2-carboxylic acid can be detected by electron capture, or mass spectrometric techniques, after gas chromatographic separation on capillary or conventional columns. A prerequisite of quin-oxaline-2-carboxylic acid analysis by gas chromatography is the derivatization of the molecule by means of esterification. Esterification has been accomplished with methanol (419, 420, 422), ethanol (421), or propanol (423) under sulfuric acid catalysis. Further purification of the alkyl ester derivative with solid-phase extraction on a silica gel column (422), thin-layer chromatography on silica gel plate (420), or liquid chromatography on Hypersil-ODS, 3 m, column (423), has been reported. 

Chlorination of 5-hydroxyquinoxaline 1,4-dioxide in methylene chloride gives the 6,8-dichloro derivative, but reaction with N-chlorosuccinimide yields 8-chloro-5-hydroxyquinoxaline dioxide. Bromination in acetic acid gives the 6,8-dibromo derivative.195 15 Side-chain bromination is observed, however, when 2,3-dimethylquinoxaline 1,4-dioxide reacts with bromine in dioxane 2,3-bis(bromomethyl)quin-oxaline 1,4-dioxide is formed.195c... 

Another report describes the synthesis of pyrazino[2,3-6]quinoxaline 1,4-dioxides (123) by condensation of furoxano[3,4-Z>]quinoxaline (121) with alkynes and alkenes. The pyrazino[2,3-A]quin-oxaline 1,4-dioxides (123) are also isolated as the final products from the reaction with alkenes and oxidation of the initially formed dihydro derivatives (122) (Scheme 21) <88JHC813>. 

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