Aminophenazines

Broadly speaking, nucleophilic substitution may be divided into (a) the direct displacement of hydrogen and (b) the displacement of other substituents. Displacements of type (a) are rare and are typified by the Tschitschibabin reaction. Pyrazine reacts with NaNHa/NHs to yield 2-aminopyrazine, but no yield has been quoted (46USP2394963). Generally, the synthesis of aminopyrazines, aminoquinoxalines and aminophenazines is more readily accomplished by alternative methods, particularly displacement of halogen from the corresponding halo derivatives, which are themselves readily available. 

All the evidence suggests that such groups always exist in the amino form, and the reactions and behavior of these compounds resemble those of aniline and the naphthylamines. For example, the amino form of 7-aminophenazin-2-ones (246) would be expected to be more stable than the imino form (247), and their weak basicity supports this expectation. ... 

On the other hand, there is at least one case of an aromatic amine without a hydroxy group in the 2-position, namely 1-aminophenazine (2.29) which, after the initial diazotization, is oxidized within minutes by air or additional nitrous acid to the quinone diazide 2.31 (Olson, 1977). 

There is no direct experimental evidence for the intermediate 2.30 in the reaction sequence of Scheme 2-19. In the corresponding diazotization of 2-aminophenazine the proportion of the quinone diazide (isomer of 2.31) amounted to only 16%, but 30% unsubstituted phenazine was also found. The phenazine may have resulted from the overall redox reaction. 

The reaction of benzofuroxans with phenols produced substituted phenazines for example, benzofuroxan 81 with phenols gave the corresponding 7- and 8-substituted-2-aminophenazine and 7- and 8-substituted-2-hydroxyphena-zine 5,10-dioxides 82 (Equation 20) <2005JME21>. 

The mutagenic aminophenazines 71 are present as impurities of carbendazim (72) fungicides and its formulations. They were determined by HPLC-UVD (diode array), using 0.02% sulfuric acid in MeOH, and measuring at 270 and 453 nm186. 

A glassy carbon electrode coated with an anodically formed polymer of 1-aminophenazine (292) mediates the reduction of Fe(III), which occurs in the region of the potential in which the reduction of... 

Rapid and sensitive HPLC methods were developed for the detection of an antimicrobial growth promoter and its main metabolites containing quinoxaline-2-carboxylic acid <2005MI1495>. The major phenazine pigments of Pseudomonas aeruginosa such as 1-hydroxyphenazine and phenazine-l-carboxylic acid <1997JCH(A)(771)99>, and 2-aminophenazine as an impurity in a bactericide <1999MI632>, were also analyzed by HPLC methods. 

The silver dye bleach reaction is very slow (65MI11401), and an additional agent is needed to promote the reaction between the immobile silver image and the immobile dye. 1,4-Diazines have been used as catalysts for this reaction, 2,3-dimethylquinoxaline (65), 2,3-diphenylpyrazine (66) and 2-hydroxy-3-aminophenazine (67) being specific examples. 

Improved Syntheses of Phenazines. Parti. 1-Aminophenazine and 1,3-Diamino-phenazine. 

Cyclization using palladium on charcoal in nitrobenzene at reflux can be used instead of iron(III) chloride to give a 34% yield of 8-aminophenazine-2-carbonitrile. ... 

Photochemical decomposition of 2-azido-l-methoxyphenazine forms singlet and triplet nitrenes, which are trapped with the azide leading in acetonitrile at —20°C to the dimeric product 3-[3-[[(l-methoxy-2-phenazinyl)imino]methoxymethyl]-2-quinoxalinyl]-2-propenenitrile <9lJOC6993>. Higher reaction temperatures result in the additional formation of aminophenazines and other 2,3-disubstituted quinoxalines <87J0C1245>. 

Clofazimine, a substituted aminophenazine dye with lepro-static properties (50 to 100 mg p.o. once daily), is indicated in the treatment of dapsone-resistant leprosy and erythema nodosum leprosum. 

Brown to yellow needles. On careful heating sublimes forming yellow leaflets, mp 264. So) in alcohol, benzene. Yields 2-aminophenazine and small amounts of pbenazine when heated with zinc dust. 

Azidophenazine is converted, on irradiation in acetonitrile in the presence of amines, into 2-alkylamino-l-aminophenazines and 2-aminophenazine. ... 

Thermal decomposition of 2-azidophenazine in hydrocarbon solvents e.g. tetralin) gives 2-aminophenazine photolysis in undegassed cyclohexane, however, gives an excellent yield of the pyrrolo-quinoxaline (290) A possible mechanism, passing through the nitrile oxide (289), has been proposed. ... 

Hydroxy-3-aminophenazine and 2,3-diaminophenazine levels in carbendazim formulations were determined using a separation generated on a Cig column (A = 254 nm) and a 75/25 water (25 mM K2HPO4 pH 7.5 with H3P04)/acetonitrile acetonitrile mobile phase. The aminophenazine was badly tailed and the peaks were not fully resolved. Elution time was 14 min. A better choice of mobile phase might have included TEA or THE as mobile phase modifiers. Standard solutions from 0.1 to 10 ppm were used and a limit of quantitation of 0.71 ppm and limit of detection of 0.6 ppm were reported [999]. 

Kelaidopoulou A, Abelidou E, Kokkinidis G (1999) Electrocatal54ic oxidation of methanol and formic acid on dispersed electrodes Pt, Pt-Sn and Pt/M (upd) in poly(2-hydroxy-3-aminophenazine). J Appl Electrochem 29 1255-1261... 

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