Oxidative of aromatic compounds

Attenlion should be drawn to ihe use of tin oxide systems as heterogeneous catalysts. The oldest and mosi extensively patented systems are the mixed lin-vanadium oxide catalysis for the oxidation of aromatic compounds such as benzene, toluene, xylenes and naphthalene in the. synthesis of organic acids and acid anhydride.s. More recenily mixed lin-aniimony oxides have been applied lo the selective oxidaiion and ammoxidaiion of propylene to acrolein, acrylic acid and acrylonilrile. 

Oxepin and its derivatives have attracted attention for several reasons. Oxepin is closely related to cycloheptatriene and its aza analog azepine and it is a potential antiaromatic system with 871-elcctrons. Oxepin can undergo valence isomerization to benzene oxide, and the isomeric benzene oxide is the first step in the metabolic oxidation of aromatic compounds by the enzyme monooxygenase. 

Hardisson C, JM Sala-Trapat, RY Stanier (1969) Pathways for the oxidation of aromatic compounds by Azotobacter. J Gen Microbiol 59 1-11. 

Reactions of partial electrochemical oxidation are of considerable interest in the electrosynthesis of various organic compounds. Thus, at gold electrodes in acidic solutions, olefins can be oxidized to aldehydes, acids, oxides, and other compounds. A good deal of work was invested in the oxidation of aromatic compounds (benzene, anthracene, etc.) to the corresponding quinones. To this end, various mediating redox systems (e.g., the Ce /Ce system) are employed (see Section 13.6). 

Scheme 12.22. Side Chain Oxidation of Aromatic Compounds... 

Intermediates generated at an electrode surface may react while still near the electrode. If so, one side of the intermediate may be wholly or partly shielded from attack by other reactants by the electrode itself. Such behavior is particularly common in the electrochemical oxidation of aromatic compounds since, as we have already seen with coumarin, aromatic compounds are generally tightly adsorbed parallel to the electrode surface at potentials positive of the p.z.c. For example, electrochemical oxidation of the stilbenes in alkaline methanol affords a mixture of dl and meso-1,2 dimethoxy-1,2-diphenylethane (1) 10>. It is found that c/s-stilbene affords a mixture of isomers of 1 in which the... 

Palmisano, G., Addamo, M., Augugliaro, V., Caronna, T., Garci a-Lopez, E., Loddo, V., and Palmisano, L. (2006) Influence of the substituent on selective photocatalytic oxidation of aromatic compounds in aqueous Ti02 suspensions. Chemical Communications (9), 1012-1014. 

Vazquez-Duhalt, R. Westlake, D. W. S., and Fedorak, P. M., Lignin Peroxidase Oxidation of Aromatic-Compounds in Systems Containing Organic-Solvents. Applied and Environmental Microbiology, 1994. 60(2) pp. 459-466. 

Fujihira, M. Satoh, Y. Osa, T. 1981. Heterogeneous photocatalytic oxidation of aromatic-compounds on Ti02. Nature 293 206-208. 

Stereocontrolled oxidation of aromatic compounds (hydroxylation or dihy-... 

Boncz, M.A., et al., Substituent effects in the Advanced Oxidation of Aromatic Compounds, in Proceedings of the International Regional Conference of the IOA, Poitiers, 1998, France. 

Scheme 38 Side-chain oxidation of aromatic compounds mediated by Fe(ll).

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... 

More drastic conditions of temperature, pressure and time gave carbon as the product from both aromatic and aliphatic compounds. This carbon is an activated char with decolorizing properties. Tars, tarry substances, the oxides of carbon, and the usual products of the oxidation of aromatic compounds (dicarboxylic acids) were all conspicuous by their absence. Benzotrifluoride oxidized to benzoyl fluoride. The aliphatic compounds cyclohexane, methycyclohexane, n-heptane, etc., could be oxidized to carbon and water. 

Besides a variety of other methods, phenols can be prepared by metal-catalyzed oxidation of aromatic compounds with hydrogen peroxide. Often, however, the selectivity of this reaction is rather poor since phenol is more reactive toward oxidation than benzene itself, and substantial overoxidation occurs. In 1990/91 Kumar and coworkers reported on the hydroxylation of some aromatic compounds using titanium silicate TS-2 as catalyst and hydrogen peroxide as oxygen donor (equation 72) . Conversions ranged from 54% to 81% with substituted aromatic compounds being mainly transformed into the ortho-and para-products. With benzene as substrate, phenol as the monohydroxylated product... 

SCHEME 142. Vanadium-catalyzed oxidation of aromatic compounds using H2O2... 

SCHEME 143. Oxidation of aromatic compounds using Re oxides as catalyst in the presence of H2O2... 

Some reactions of 2,2 -bipyridine /V-oxides have been reported. The l,T-dioxide is nitrated readily to 4,4 -dinitro-2,2 -bipyridine 1,T-dioxide. ° ° °" 2,2 -Bipyridine 1-oxide is also nitrated in the 4 position. The nitro groups in 4,4 -dinitro-2,2 -bipyridine l,T-dioxide are reactive, being replaced by chlorine with concentrated hydrochloric acid," by bromine with acetyl bromide, by hydroxyl with dilute sulfuric acid, and by alkoxy groups with sodium alkoxides. Some of the dialkoxy derivatives are useful catalysts for the oxidation of aromatic compounds. The dinitro dioxide is deoxygenated to 4,4 -dinitro-2,2 -bipyridine with phosphorus trichloride in chloroform, and other substituted l,T-dioxides behave similarly, but with phosphorus trichloride alone, 4,4 -dichloro-2,2 -bipyridine results. The dinitro dioxide is reduced by iron powder in acetic acid to 4,4 -diamino-2,2 -bipyridine, whereas 4,4 -dichloro-2,2 -bipyridine l,T-dioxide is converted to its 4,4 -diamino analogs with amines. Related reactions have been described. ... 

F. Effenberger, Acc. Chem. Res. 22,27-35 (1989) l,3,5-Tris(dialkylamino) benzenes Model Compounds for the Electrophilic Substitution and Oxidation of Aromatic Compounds". 

The electrochemical oxidations of aromatic compounds in the presence of a fluoride ion sources have been widely studied by a number of workers to produce a range of partially fluorinated compounds [9-12]. 

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