Oxidation primary aromatic amines

Oxidation. The reagent oxidizes primary aromatic amines in benzene solution at room temperature to azo compounds (1 -2 days), but yields are variable toluidines, 42, 56, and 6% p-nitroaniline (53%) a-naphthylamine, 3%. Oxidations in acetic... 

Poly(phenylene oxides) are produced by the oxidative coupling of 2,6-disubstituted phenols. The polymers are also known as poly(oxyphenylenes) or poly(phenyl ethers), and, in the case of dimethyl compounds, also as poly(xylenols). Copper (I) salts in the form of their complexes with amines catalyze the reaction. Primary and secondary aliphatic amines must be used at low temperatures, since otherwise they are oxidized. Primary aromatic amines are oxidized to azo compounds, and secondary aromatic compounds probably to hydrazo compounds. Pyridine is very suitable. 

Nitroso compounds are formed selectively via the oxidation of a primary aromatic amine with Caro s acid [7722-86-3] (H2SO ) or Oxone (Du Pont trademark) monopersulfate compound (2KHSO KHSO K SO aniline black [13007-86-8] is obtained if the oxidation is carried out with salts of persulfiiric acid (31). Oxidation of aromatic amines to nitro compounds can be carried out with peroxytrifluoroacetic acid (32). Hydrogen peroxide with acetonitrile converts aniline in a methanol solution to azoxybenzene [495-48-7] (33), perborate in glacial acetic acid yields azobenzene [103-33-3] (34). 

By reaction of a primary aromatic amine—e.g. aniline 1—with glycerol 2, and a subsequent oxidation of the intermediate product 4, quinoline 5 or a quinoline derivative can be obtained.As in the case of the related Friedlander quinoline synthesis, there are also some variants known for the Skraup synthesis, where the quinoline skeleton is constructed in similar ways using different starting materials. ... 

In a related reaction, primary aromatic amines have been oxidized to azo compounds by a variety of oxidizing agents, among them Mn02, lead tetraacetate, O2 and a base, barium permanganate, and sodium perborate in acetic acid, tert Butyl hydroperoxide has been used to oxidize certain primary amines to azoxy compounds. 

As the anhydride of nitrous and perchloric acids, it is a very powerful oxidant. Pinene explodes sharply acetone and ethanol ignite, then explode ether evolves gas, then explodes after a few s delay. Small amounts of primary aromatic amines-aniline, toluidines, xylidines, mesidine-ignite on contact, while larger amounts exploded dangerously, probably owing to rapid formation of diazonium perchlorates. Urea ignites on stirring with the perchlorate, (probably for a similar reason). 

Almost all drugs that contain a primary aromatic amine or aromatic nitro group are associated with a significant incidence of adverse reactions (5), presumably because they are oxidized or reduced, respectively, to similar reactive intermediates examples are shown in Figure 8.5. 

Anilines are converted into nitrosoarenes ArNO by the action of hydrogen peroxide in the presence of [Mo(0)(02)2(H20) (HMPA)]224, whereas catalysis of the reaction by titanium silicate and zeolites results in the formation of azoxybenzenes ArN (0)=NAr225. Azo compounds ArN=NAr are formed in 42-99% yields by the phase-transfer assisted potassium permanganate oxidation of primary aromatic amines in aqueous benzene containing a little tetrabutylammonium bromide226. The reaction of arylamines with chromyl chloride gives solid adducts which, on hydrolysis, yield mixtures of azo compounds, p-benzoquinone and p-benzoquinone anils 234227. 

The effect of pH on the periodate oxidation of seven anilines has been investigated. " The kinetics of periodate oxidation of aromatic amines have been studied. " - " Periodate oxidation of oxalic acid is catalysed by Mn(II). " The reaction of ethane-1,2-diol with periodate has been investigated under a variety of conditions and the results compared with those of earlier work and analogous studies on pinacol. " The 104 ion is the primary reactant, with H5IO6 as a secondary reactant the reverse is true for pinacol. The complex observed in previous work is shown not to be an intermediate, but rather to deactivate the reactants. 

Laha, S. and Luthy, R.G. Oxidation of aniline and other primary aromatic amines by manganese dioxide. Environ. Sci. TechnoL, 24(3) 363-373, 1990. 

Nitrobenzene chloride, sulfonylperoxy radical reactions, 1035, 1036 2-Nitrobenzenesulfinylperoxy intermediate, superoxide reactions, 1034 Nitrogen-containing compound oxidation bis(trimethylsilyl) peroxide reactions, 802-3, 804 dioxiranes, 1151-5 primary aromatic amines, 1151 A-oxidation, 531-8, 539 Nitrohpids, hpid hydroperoxides, 952-4 Nitronate ions, dioxirane oxidation, 1152-3 Nitrosation, malondialdehyde, 667 Nitroso compounds, spin trapping, 664 Nitrotyrosine, peroxynitiite determination, 740-1... 

As is well known, the oxidation of primary aromatic amines is a highly complex process, depending on exact reaction conditions to produce well-defined products—usually complex dyes. A few synthetic procedures have been reported in which amines have been converted into azo compounds. 

Primary aromatic amines may be oxidized with Caro s acid or a variety of peracids (Eq. 4). 

Whenever only primary amines need to be derivatized, fluorescamine often constitutes the reagent of choice. Fluorescamine, although nonfluorescent itself, can react with primary amines forming highly fluorescent pyrrolinones (139-144). Aliphatic primary amines favor derivatization reaction at pH 8-9, whereas primary aromatic amines exhibit optimal reactivity at pH 3-4. Secondary amines are also fully reactive with fluorescamine but their products do not fluoresce. However, secondary amines can be detected with fluorescamine if they are converted to primary amines by oxidation with N-chlorosuccinimide prior to their fluorescamine derivatization (145, 146). Alcohols can also interact with fluorescamine but this reaction is reversible as a result, alcohols just slow down the reaction rate of fluorescamine with primary amines. On the other hand, tertiary amines and guanidines are not reactive at all with fluorescamine. 

For reviews on the oxidation of amines, see Rosenblatt Burrows, in Patai The Chemistry of Functional Groups, Supplement F, pt. 2 Wiley New York, 1982, pp. 1085-1149 Challis Butler, in Patai The Chemistry of the Amino Group Wiley New York, 1968, pp. 320-338. For reviews confined to primary aromatic amines, sec Hcdayalullah Bull. Soc. Chim. Fr. 1972, 2957 Surville Jozefowicz Buvet Ann. Chem. (Paris) 1967, [14] 2, 149-157. 

The reduction of nitro groups may also be catalyzed by microsomal reductases and gut bacterial enzymes. The reduction passes through several stages to yield the fully reduced primary amine, as illustrated for nitrobenzene (Fig. 4.39). The intermediates are nitrosobenzene and phenylhydroxylamine, which are also reduced in the microsomal system. These intermediates, which may also be produced by the oxidation of aromatic amines (Fig. 4.21), are involved in the toxicity of nitrobenzene to red blood cells after oral administration to rats. The importance of the gut bacterial reductases in this process is illustrated by the drastic reduction in nitrobenzene toxicity in animals devoid of gut bacteria, or when nitrobenzene is given by the intraperitoneal route. 

In the reactions listed in Table 3, Michael addition of a primary aromatic amine to an a, (3-unsaturated aldehyde or ketone (prepared in situ) is followed by cyclization and oxidation of the intermediate dihydroquinoline to a quinoline (138 — 141). 

Reaction XCIII. Oxidation of Primary Aromatic Amines and their para-substituted Derivatives to Quinones. (A., 27, 268 194, 202 211, 49 215, 125 B., 19, 1467 20, 2283 25, 982 36, 4390.)—Many primary aromatic amines, when oxidised with chromic acid, readily yield p-quinones, aniline, for example, giving p-benzoquinone. 

Dess and Martin reported that their name reagent reacts with primary amines giving insoluble products, which are difficult to analyze. Nevertheless, there are several reports of oxidation of alcohols, in which primary aromatic amines remain unaffected.47 In these cases, when an aldehyde is obtained, sometimes it is attacked by the amine, resulting in the formation of nitrogen heterocycles.48 There is one report49 in which an alcohol is oxidized to an aldehyde in the presence of a primary aliphatic amine that reacts in situ with the aldehyde. 

Catalysis by cobalt(III) has been the subject of several papers.185-187 The N.N-bis(sahcyldene)ethylnediaminocobalt(III)-catalysed oxidative carbonylation of o-, m-and -substituted primary aromatic amines in MeOH gives ureas, isocyanates, carbamates, and azo derivatives. A Hammett p value of —0.5 for the reaction indicates that electrophilic attack of CO at a nitrogen anion complexed to Co in the TS is... 

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