Alloxazine 5-oxides

Alloxazine 5-oxides s. 29, 337 also fervenulin 4-oxides from 6-benzylidenehydra-zino-l,3-dimethyluracils s. Chem. Pharm. Bull. 24, 338 (1976)... 

Anilinouracil heated 0.5 hr. at 90 with an equimolar amount of KNOg in acetic acid in the presence of some H2SO4 alloxazine 5-oxide. Y 90%. F. e. s. F. Yoneda and Y. Sakuma, Chem. Pharm. Bull. 21, 448 (1973) 22, 1652 (1974). 

Alloxan forms an oxime (1007) which is the same compound, violuric acid, as that formed by nitrosation of barbituric acid likewise, a hydrazone and semicarbazone. Reduction of alloxan gives first alloxantin, usually formulated as (1008), and then dialuric acid (1004 R = OH) the steps are reversible on oxidation. Vigorous oxidation with nitric acid and alkaline hydrolysis both give imidazole derivatives (parabanic acid and alloxanic acid, respectively) and thence aliphatic products. Alloxan and o-phenylenediamine give the benzopteridine, alloxazine (1009) (61MI21300). 

When the central ring is rendered aromatic by oxidation, e.g., the phenoxazinium and phenothiazinium ions 119 (X = 0 and S), planarity is found as expected. The same effect is seen with alloxazine 120, which is planar, and dihydroalloxazine 121, which is not. 

Allene, perfluoro-, cycloaddition to phenylsydnone, 59, 12 Allene, phenylsulfinyl-, cycloaddition of nitrile oxides, 60, 276 Alloxan, structure, 55, 133 Alloxazines, synthesis, 55, 186 Allyl alcohols, ethers, chiral,... 

Quinoxaline hydroxy-JV-oxides (l-hydroxyquinoxalin-2-ones) have been prepared by alkaline hydrolysis of alloxazine N-oxides (Scheme... 

Other lH-2,3-dihydro 2-oxo compounds have been prepared by more specialized routes. Reaction of quinoxaline N-oxide (61) with phenyl isocyanate gives a mixture of anilinoquinoxaline 62 and the (presumably) derived diphenyl oxo compound 63. Recently it has been shown that the alloxazine derivative (64) on treatment with di-n-butylamine undergoes a Lossen rearrangement to give the 2-oxo compound 65. Alkali treatment of compound 65 gives the 1,3-unsubstituted product 59. 

Oxidation with the anion of hydrogen peroxide (HO — O ) converts isoalloxazine-8-sulfonic acids (2) into 8-hydroxy-alloxazines (3). This reaction, which has been described recently by Smith et al. (168) is typical for electron deficient sulfonic acids (178) and apparently does not occur at the less activated position 6. 

Mager, H. I. X., and W. Berends Hydroperoxides of Partially Reduced Quinoxalines, Pteridines and (Iso)alloxazines Intermediates in Oxidation Processes. Rec. Trav. Chim. 84, 1329(1965). 

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