Aromatic compound oxidation

Rate Constants of Aromatic Compounds Oxidation by sec-Decylsulfonyl... 

One of numerous examples of LOX-catalyzed cooxidation reactions is the oxidation and demethylation of amino derivatives of aromatic compounds. Oxidation of such compounds as 4-aminobiphenyl, a component of tobacco smoke, phenothiazine tranquillizers, and others is supposed to be the origin of their damaging effects including reproductive toxicity. Thus, LOX-catalyzed cooxidation of phenothiazine derivatives with hydrogen peroxide resulted in the formation of cation radicals [40]. Soybean LOX and human term placenta LOX catalyzed the free radical-mediated cooxidation of 4-aminobiphenyl to toxic intermediates [41]. It has been suggested that demethylation of aminopyrine by soybean LOX is mediated by the cation radicals and neutral radicals [42]. Similarly, soybean and human term placenta LOXs catalyzed N-demethylation of phenothiazines [43] and derivatives of A,A-dimethylaniline [44] and the formation of glutathione conjugate from ethacrynic acid and p-aminophenol [45,46],... 

A broad spectrum of chemical reactions can be catalyzed by enzymes Hydrolysis, esterification, isomerization, addition and elimination, alkylation and dealkylation, halogenation and dehalogenation, and oxidation and reduction. The last reactions are catalyzed by redox enzymes, which are classified as oxidoreductases and divided into four categories according to the oxidant they utilize and the reactions they catalyze 1) dehydrogenases (reductases), 2) oxidases, 3) oxygenases (mono- and dioxygenases), and 4) peroxidases. The latter enzymes have received extensive attention in the last years as bio catalysts for synthetic applications. Peroxidases catalyze the oxidation of aromatic compounds, oxidation of heteroatom compounds, epoxidation, and the enantio-selective reduction of racemic hydroperoxides. In this article, a short overview... 

Naphthenic and aromatic compounds oxidize to form high-molecular-weight deposits... 

Another way to prevent any dissociation of cyclization products obtained by the diaddition reactions is their conversion into aza-aromatic compounds. Oxidation of cycloadducts by permanganate in acetone yields condensed pyrazine derivatives containing, of course, no ring junction hydrogen atoms. Several examples of condensed systems obtained by this method are shown in Scheme 53. 

On the whole it is easier to use the saturated 1,5-diketone and oxidize the product to the pyridine. As we are going from a nonaromatic to an aromatic compound, oxidation is easy and we can replace the question mark above with almost any simple oxidizing agent, as we shall soon see. 

Hydroxylation of aromatic compounds Oxidation of benzene or phenol... 

Water-soluble macromolecular metal complexes based on terminally functionalized ethylene oxides and ethylene oxide-propylene oxide block copolymers have been used as catalysts for hydroformylation, hydrogenation, Wacker oxidation of imsaturated compounds, hydroxylation of aromatic compounds, oxidation of saturated and alkylaromatic hydrocarbons, metathesis, Heck reaction, and some asymmetric reactions. 

These data show that under atmospheric conditions the adducts will react predominantly with O2 to form hydroxycyclohexadienylperoxy radicals. The subsequent reactions of these peroxy radicals leading to ring-opening are still unclear. Several possible reaction pathways which result in formation of dicarbonyl and unsaturated dicarbonyl compounds are outlined in Fig. 10. Experiments on radical cycling (Zetzsch) indicate that the reaction of the aromatic-OH adducts with O2 produce HO2 radicals with high yield on a short timescale. The mechanism leading to this so-called "prompt HO2" formation in the aromatic compound oxidation systems is presently unclear. 

Careful attempts to detect hydroperoxides and peroxynitrates, expected products of the reactions of the hydroxycyclohexadienylperoxy radicals with HO2 and NO2, respectively, were unsuccessful. This has been taken, in conjunction with work on the effect of NOx on the kinetics and products of the aromatic compound oxidation, as an indication that such peroxy radicals are very short-lived. It has been suggested, therefore, that the peroxy radicals are not able to oxidise NO as is the case for alkane and alkene atmospheric oxidation. 

A good number of reviews, perspectives, highlights, focus, and account of research were published in the period under review. The topics covered included nitfation of aromatic compounds, oxidation processes, Pd catalysis, oxidative coupling, asymmetric transfer hydrogenation, Sm-Barbier reaction, use of hypervalent I2, and Bayer-Villiger reaction. 

Perfluorobenzenium salt can be conveniently prepared from the reaction of 1,4-perfluorocyclohexadiene with SbFs. " In the presence of SbFs, this salt is able to react with three equivalents of pentafluorobenzene to yield perfluoro-1,3,5-triphenylbenzene (eq 3). " When 2,2 -di-Ff-octafluorobiphenyl is used as the substrate, perfluorotriphenylene is obtained in 50% yield (eq 4). Per-fluoronaphthlenenium ion also reacts with polyfluorinated arenes in a similar fashion. " The above reaction offers a facile approach for the preparation of these perfluorinated polynuclear aromatic compounds. Oxidation of perchlorobenzene with SbFs in the presence of pentafluorobenzene leads to the formation of coupling products. ... 

I. Aromatic compound + oxidized catalyst —> oxidation product + reduced catalyst... 

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