Phenazine, structure

Azonia substitution at a naphthalene bridgehead position gives the quinolizinium ion (16). Oxonia substitution, elsewhere, forms the 1- and 2-benzopyrylium ions (17) and (18). The two most well-known monoaza systems with three aromatie fused rings are aeridine (19), derived structurally from anthraeene, and phenanthridine (20), an azaphenanthrene. The better-known diaza systems inelude phenazine (21) and 1,10-phenanthroline (22), while systems with three linearly fused pyridine rings are ealled anthyridines, e.g. the 1,9,10-isomer (23). 

In valence bond terms the pyrazine ring may be represented as a resonance hybrid of a number of canonical structures (e.g. 1-4), with charge separated structures such as (3) contributing significantly, as evidenced by the polar character of the C=N bond in a number of reactions. The fusion of one or two benzene rings in quinoxaline (5) and phenazine (6) clearly increases the number of resonance structures which are available to these systems. 

Phenazine also exhibits D h symmetry and numerous reports on the X-ray structure of a-phenazine have appeared (54AX129). The parameters determined at 80 K are shown in... 

In the case of phenazine, substitution in the hetero ring is clearly not possible without complete disruption of the aromatic character of the molecule. Like pyrazine and quinoxa-line, phenazine is very resistant towards the usual electrophilic reagents employed in aromatic substitution reactions and substituted phenazines are generally prepared by a modification of one of the synthetic routes employed in their construction from monocyclic precursors. However, a limited range of substitution reactions has been reported. Thus, phenazine has been chlorinated in acid solution with molecular chlorine to yield the 1-chloro, 1,4-dichloro, 1,4,6-trichloro and 1,4,6,9-tetrachloro derivatives, whose gross structures have been proven by independent synthesis (53G327). 

X-ray structure, 3, 158-159 Phenazin-l(2H)-one, 3,4-dihydro-synthesis, 2, 69 Phenazopyridine, 1, 145 as urinary tract analgesic, 2, 517 Phenbenzamine as antihistamine, 1, 177 Phencyclidine... 

Isolated and benzo-fused diazine rings are key structural elements in many natural and synthetic compounds of current interest. This contribution relates highlights from many of the studies on the diazines pyridazine, pyrimidine, pyrazine, and their benzo-fused derivatives cinnoline, phthalazine, quinazoline, quinoxaline, and phenazine published in English in the journal literature during 1996, as covered by Chem. Abstr. through volume 126, issue 5. 

Phenazines — These are dibenzopyrazine derivatives with fnnctional groups (hydroxy-, carboxy-) at C, and Cg and an oxygen or methyl gronp at Nj and N,o. There are also more complex structures, substituted phenazines, terpenoidal, and carbohydrate-containing phenazines and phenazines derived from saphenic acid. ... 

Second only to sulfur-based systems, nitrogen complexes are relatively well represented in the structural literature with 41 complexes reported. Of these, 25 are with I2 as the electron acceptor, 11 are with the interhalogen IC1, three are with Br2, and two are with IBr. As expected, in every case the halogen bond forms between the nitrogen and the softest halogen atom, i.e., iodine, in all of the complexes except those with dibromine. Most N I2 complexes, and all N Br2, N IBr, and N IC1 complexes are simple adducts, mode A. Exceptions for the diiodine complexes include bridging mode (B) observed for diazines, such as pyrazine [86], tetramethylpyrazine [86], phenazine, and quinoxaline [87], and for 9-chloroacridine [89] and the 1 1 complex of diiodine with hexamethylenetetramine [144] and amphoteric bridging mode (BA) observed for 2,2 -bipyridine [85], acridine [89], 9-chloroacridine [89], and 2,3,5,6-tetra-2/-pyridylpyrazine [91]. The occurrence of both B and BA complexes with 9-chloroacridine, and of B and A complexes and an... 

The DNA binding of [cp Ir(dppz)(Aa)]"+, dppz = dipyrido[3,2-a 2, 3 -c]phenazine, Aa = S-coor-dinated amino acid or peptide, has been investigated by UV-vis spectroscopy, 2D-NOESY, and gel electrophoresis. The complexes intercalate into DNA adjacent to T2 from the major groove. The X-ray structural data for [cp IrCl(dppz)](CF3S03)4 and [ cp Ir(9-EtG)(Phen)](CF3S03)2, where GH = guanine, are reported.423... 

Azaquinone structures possessing two adjacent carbonyl groups provided phenazine derivatives, e.g., 58 and 59, when reacted with o-pheny-lenediamine (Scheme 16) [63JOC260 72JCS(P 1)977]. 

A naturally occurring phenazine of nonbacterial origin is the methano-phenazine (MP) (10) which has been isolated from the cytoplasmic membrane of Methanosarcina (Ms.) mazei Gol archaea. The structure, synthesis, properties, and function of this natural product will be discussed in detail since it is not only the first and so far the sole phenazine derivative from archaea, but also the first one that is acting as an electron carrier in a respiratory chain - a biologic function equivalent to that of ubiquinones in mitochondria and bacteria. 

In addition, the idea of the terpenoid side chain of 10 essentially assisting in anchoring the coenzyme in the cytoplasmic membrane without having any impact on the redox potential was to be explored. To this end, a number of phenazine ethers 44a-g were synthesized by Williamson ether synthesis and then investigated by electrochemical methods. And indeed, we were able to identify a good match between the redox potentials of the various phenazine ethers, which turned out to be independent of the side chain structure. 

The more recently discovered and most unusual structures include the dimeric phenazine derivatives esmeraldin A (52) and esmeraldin B (53), which are produced by Streptomyces antibioticus Tii 2706 together with 49 [54]. Esmeraldins exhibit no antibacterial activity but 53 is effective against tumor cells. Much effort has been directed to the elucidation of the biosynthesis of the esmeraldins [55]. Some rare L-quinovose esters (55a-d) of saphenic acid have... 

As part of a screening program for bioactive compounds from endosym-biontic microorganisms, Zeeck et al. successfully isolated a group of new, structurally related phenazine antibiotics, the so called endophenazines A (74), B (75), C (76), and D (77) from the arthropod-associated endosymbiont Strepto-... 

Quite recently, the structure of pelagiomicins B (60) and C (61) was confirmed by a synthesis starting from griseoluteic acid (62) [60]. In the first synthesis of 62, Holliman et al. employed the reductive cyclization of o-nitrodi-phenylamines using NaBH4 to yield phenazines [84]. To this end, 3-amino-4-methoxybenzyl alcohol (99) was treated with methyl 2-bromo-3-nitrobenzoate (100) to yield the o-nitrodiphenylamine 101, which by reductive cyclization... 

Soil A reversible equilibrium is quickly established when aniline covalently bonds with humates in soils forming imine linkages. These quinoidal structures may oxidize to give nitrogen-substituted quinoid rings. The average second-order rate constant for this reaction in a pH 7 buffer at 30 °C is 9.47 x 10 L/g-h (Parris, 1980). In sterile soil, aniline partially degraded to azobenzene, phenazine, formanilide, and acetanilide and the tentatively identified compounds nitrobenzene and jD-benzoquinone (Pillai et ah, 1982). 

The preparation and structure of [Ru(phen)2(l,5,6,10-tetraazaphenanthrene)]Cl2 have been reported NMR spectroscopic data provide insight into the hydrophilic properties of the complex. The bpy-containing complexes [Ru(bpy)2(92)] + and [ Ru(bpy)2 2(M 92)] ((92) = dipyrido(2,3-a 2, 3"-/z)phenazine) were described earlier in the chapter.The analogous [Ru(phen)2(92)] and [ Ru(phen)2 2(M 92)]" have also been prepared and characterized, as has [ (phen)2Ru(/i-92) 3Ru] +. The electronic spectra exhibit intense MLCT bands in the visible region the electrochemical properties of the complexes have been investigated and for [ (phen)2Ru(/i-92) 3Ru], two sets of reduction waves centered on ligand (92) are separated by those assigned to phen reductions. ... 

Theoretical calculations have been a successful approach for the description of structures and thermochemistry for a wide variety of chemical substances in fact, the theoretical methods have greatly increased in importance for investigating various properties of pyrazines, quinoxalines, and phenazines <1996CHEC-II(6)233>. In most cases, the calculated results have been discussed in comparison with spectroscopic properties accordingly, in this chapter, such examples are shown in each section on spectroscopy. 

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