Azoxybenzenes, complexes

The logical conclusion reached while considering these data is as follows. In liquid phase (THF), under the conditions of a regular volume continuum without gradients of concentration and potential, all anion-radicals of azoxybenzene can be stabilized just after formation due to their bonding with potassium cations. This yields the coordinative complex. The complex is diamagnetic and, therefore, azoxybenzene anion-radicals cannot be revealed by ESR spectroscopy (Scheme 2.15). 

The diamagnetic complex is not reduced further by the cyclooctatetraene dianion. This prevents the conversion of the azoxybenzene anion-radicals into azodianions. Potassium cation plays an important role in this limitation of the reduction process, which, generally, proceeds readily (the... 

The removal of potassium cations makes the results of the liquid-phase and electrode reactions similar. In the presence of crown ether, the eight-membered complex depicted in Scheme 2.16 is destroyed. The unprotected anion-radicals of azoxybenzene are further reduced by cyclooctatet-raene dianion, losing oxygen and transforming into azodianion. The same particle is formed in the electrode reaction shown in Scheme 2.13. In the chemical reduction, stabilization of azodianion is reached by protonation. Namely, addition of sulfuric acid to the reaction results in the formation of hydrazobenzene, which instantly rearranges into benzidine (4,4 -diamino-l,l"-diphenyl). The latter was isolated from the reaction, which proceeded in the presence of crown ether. 

Argenlalion chromalography, 261 Aromatic acids in human urine, 285 Aromatic hydrocarbons, 69 Arylhydroxylamines, 298 Ascorbic acid, 296 Aspirin, 282 Asymmetric diens, 290 Asymmetrical peaks, 58, 82, 160 AIT, stability constants of metal complexes. 278 Atrazine, 292 Atropine, 297 Axial diffusion mobile phase. 8 stationary phase, 8,9 Aza-arenes, 293 Azoxybenzenes, 298... 

Organic nitroso compounds insert exclusively on the Ti-C(sp3) side of titanacyclobutene complexes (Scheme 6) < 1994ICA305>. The 2-oxa-3-azatitanacyclohexene intermediate 49 can be hydrolyzed to the allylic hydroxylamine 50 or converted to azoxybenzene in the presence of excess nitrosobenzene, in an unusual reaction of indeterminant mechanism. 

Scheme 9 that both the molybdenum and iron complexes can catalyze the allylic amination of nonfunctionalized alkenes with an ene-like transposition of the double bond, but also that the yield of the allyl amine formed, 113, is moderate to high. It is generally found that higher substituted alkenes tend to give the best yields, and un-symmetrical alkenes (trisubstituted) react with virtually complete regioselectivity, as only one isomer is detected. The byproducts are primarily azoxybenzene and aniline, which arise from condensation of nitrosobenzene with phenyl hydroxylamine and reduction of phenyl hydroxylamine, respectively. 

There are several recent methods for the reduction of azobenzene to hydrazobenzene in near-quantitative yield. Samarium(II) iodide reduces azobenzene to hydrazobenzene rapidly at room temperature. Hydrogen telluride, generated in situ from aluminum telluride and water, reduces both azobenzene and azoxybenzene to hydrazobenzene a mixture of phenyllithium and tellurium powder has been used to reduce azobenzene. A complex of the coenzyme dihydrolipoamide and iron(II) is also effective for the reduction of azo- and azoxy-benzene to hydrazobenzene the reduction probably involves coordination of the azobenzene to iron(II) as shown in structure (1). Electrochemical reduction has been used to prepare a number of hydrazobenzenes from the corresponding azobenzenes. In the presence of an acylating agent a diacylhydrazine (e.g. the pyridazinedione derivative 2) can be isolated from the electrochemical reduction of azobenzene. 

Back in 1899, Werner and Stiasny (49) had studied the action of nitric acid on azobenzene and produced a series of nitro-azobenzenes and nitro-azoxybenzenes, but Werner carried the work no further. Werner then became interested in the analogy between the lakes of mordant dyes and the metallic derivatives of /3-diketones and proposed the view that mordant dyes were internal metallic complexes. This resulted in three papers published in the 1908-09 period. The first (43) reporting the complex metal salts formed from oximes, diketones, and several metals, came to the conclusion that the formation of mordant dyes depends on the formation of complex metal salts. He found that dyes capable of combining with mordants possessed both a salt-forming complex and a group capable of forming a coordinate link with a metal ion. 

Occasionally, the reaction is complex and affords a multitude of products. For example, 2,4-dichloronitrobenzene and benzyl cyanide produce a mixture containing bis(4-chloro-2-benzoyl)azoxybenzene, 2-benzoyl-4-chlo-ronitrobenzene, 5,7-dichloroanthranil, and a-(5-chloro-2-nitrophenyl) benzyl cyanide.180 Using sodium hydride in dimethylsulfoxide as the base, the substituted benzyl cyanide, formed by direct nucleophilic displacement of chloride, becomes the major product (48%), whereas with sodium hydroxide and benzyltriethylammonium chloride the dichloroanthranil (33%) predominates. 

Rearrangement of azoxybenzenes. SbCU and azoxybmzene in CCU form an orange 1 1 complex (9S.57o yield), which when heated for 5 hours at 86-88° rearranges mainly to o-hydroxyazobenzene. Rearrangement of azoxybenzenes-... 

In the reaction with nitrosobenzene, azoxybenzene and Ni(PhN02>2 are formed. The nickel complex is an interesting example of a" coordination compound of a nitro derivative with a zerovalent metal. The X-ray analysis of this compound has been undertaken 383, but the final structure has not yet been reported. The reaction with Bu NC can be carried out catalytical 1y. Thus a mixture of PhNO and Bu NC in benzene, in the presence of a catalytic amount of NiCBu NO at reflux, produces Bu NC0( SOX based on PhNO) along with PhN=C=NBu, PhN=NPh and [Pg.105]

Nitrosobenzene complexes such as RhCl(COD)2 are catalysts -for the carbonyl at i on at atmospheric pressure o-f nitrosobenzene in ethanol at 75 "C, to give azoxybenzene In these cases the amounts o-f CO2 evolved were in accord with the stoichiometry ... 

The anaerobic metabolites of 2,4-dinitrotoluene and 2,6-dinitrotoluene (2,6-diami-notoluene, 2-hydroxylamino-6-nitrotoluene, 2-nitroso-6-nitrotoluene, 2-amino-6-nitrotoluene, 3,3 -diamino-2,2 -dimelhylazoxybenzene, 2,2 -dimethyl-3,3 -dinitro-azoxybenzene) were baseline resolved on a C g column (2 = 250nm) using a complex 65-min 15/85 - 60/40 acetonitrile/water gradient [944], Detection limits of 5 ng injected were reported. A linear concentration range of 5-50 ng injected was generated. 

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