3-Methylquinoxaline-2-carboxaldehyde 1,4-dioxide

Quinoxaline 1,4-dioxide (Quindoxin) has higher antibacterial activity under in vivo than under in vitro conditions. It has been shown that its in vitro activity is enhanced 10 to 100-fold under anaerobic conditions. Derivatives of 3-methylquinoxaline 2-carboxaldehyde 1,4-dioxide such as the N-methylnitrone 86 also have higher in vivo activity than would be expected from in vitro tests. The high in vivo activity of 2,3-dimethyl-quinoxaline 1,4-dioxide is due to the formation of active metabolites, the mono- and dihydroxymethyl derivatives 87 and 88. However the hydroxymethyl derivative of 86 did not show the expected enhanced activity. Compound 88 is referred to in the literature as Dioxidine, and 2,3-bis(acetoxymethyl)quinoxaline 1,4-dioxide is known as Quinoxidine. The trade name for the 2-carboxaldehyde 1,4-dioxide derivative (89) is Car-badox. Of the numerous quinoxaline 1,4-dioxide derivatives patented in... 

Quinoxaline-2-carboxaldehydes are conveniently prepared either from the corresponding methyl- or polyhydroxyalkylquinoxalines. The oxidation of methylquinoxalines to quinoxalinecarboxaldehydes is usually carried out with selenium dioxide, and sodium metaperiodate (NaI04) is the reagent recommended for the oxidation of tetrahydroxybutyl-quinoxalines. An indirect method for the conversion of methylquinoxalines into quinoxalinecarboxaldehydes is illustrated in Scheme 1. 

Selenium dioxide oxidation of 2-methylquinoxaline yields quinoxaline-2-carboxaldehyde, and 3-methylquinoxaline-2-carboxaldehyde has been similarly prepared from 2,3-dimethylquinoxaline. Dimethylsulfoxide oxidation of 2,3-bis(bromomethyl)quinoxaline yields the furoquinoxaline 45, and this on sublimation gives quinoxaline-2,3-dicarboxaldehyde. 3-Dibromomethylquinoxaline-2-carboxaldehyde (46) is a by-product of the oxidation reaction. Direct selenium dioxide oxidation of 2,3-dimethylquinoxaline appears to be a less satisfactory method of preparing the dialdehyde. ... 

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