Mediated oxidation

As an e.xtension of the oxidative carbonylation with alkyl nitrites, malonate can be prepared by the oxidative carbonylation of ketene (583)[524], Also, the acetonedicarboxylate 585 is prepared by the Pd-catalyzed, alkyl nitrite-mediated oxidative carbonylation of diketene (584)[525],... 

Coupling the mediator s oxidation or reduction to an acid-base, precipitation, or complexation reaction involving the analyte allows for the coulometric titration of analytes that are not easily oxidized or reduced. For example, when using H2O as a mediator, oxidation at the anode produces H3O+... 

Asymmetric aziridination of a,P-unsaturated esters by use of N-nitrenes was studied in great detail by Atkinson and co-workers [34, 35]. Here, lead tetraacetate-mediated oxidative addition of N-aminoquinazolone 30 (Scheme 3.10) to a-methy-lene-y-butyrolactone 32 was reported to proceed with complete asymmetric indue-... 

Cyclodextrin mediated oxidation ofprochiral sulphides by achiral oxidation reagents leads also to optically active sulphoxides (e.e. up to 30%). When oxidation was carried out in pyridine the highest optical purities were obtained294 with hydrogen peroxide, whereas in water the best results were observed with m-chloroperbenzoic acid295.. 

Carbonaceous Deoxygenation. In this process microorganisms, principally bacteria, enzymatically mediate oxidation of simple and complex organic substances according to first order decay kinetics. 

Nitrification. Nitrification refers to biologically mediated oxidation of reduced nitrogen to higher oxidation states ... 

Enzyme-mediated oxidation reactions offer highly diverse options for the modification of existing functional groups as well as for the introduction of novel function in chiral catalysis. Biooxidations often enable us to obtain complementary solutions to metal-assisted transformations and organocatalysis and are considered one of the important strategies of green chemistry . 

A successful case study for asymmetric nitrogen oxidation was reported for a series of (hetero)aromatic tertiary amines. High diastereoselectivity was observed for the enzyme-mediated oxidation of S-(—)-nicotine by isolated CHMOAdneto to give the corresponding ds-N-oxide [215]. The stereoselectivity of this biooxidation was complementary to the product obtained by flavin M O (FM O) from human li ver (trows-selective [216]) as well as unspecific oxidations by FMOs from porcine and guinea pig liver. 

The beauty of bromide-mediated oxidations is that they combine mechanistic complexity with practical simplicity and, hence, utility. They involve an intricate array of electron transfer steps in which bromine atoms function as go-betweens in transfering the oxidizing power of peroxidic intermediates, via redox metal ions, to the substrate. Because the finer mechanistic details of these elegant processes have often not been fully appreciated we feel that their full synthetic potential has not yet been realized. Hence, we envision further practical applications in the future. 

The oxidation of an anthracene suspension in sulfuric acid conducted in the presence of cerium salts can serve as an example of mediated oxidation. In the bulk solution the Ce" ions chemically oxidize anthracene to anthraquinone. The resulting Ce ions are then reoxided at the anode to Ce". Thus, the net result of the electrochemical reaction is the oxidation of anthracene, even though the electrochemical steps themselves involve only cerium ions, not anthracene. Since the cerium ions are regenerated continuously, a small amount will suffice to oxidize large amounts of anthracene. 

The participation of nitric oxide in cell free and its restriction on macroph je mediated oxidation of LDL. Biochim. Biophys. Acta 1180, 73-82. 

Jessup, W., Simpson, J.A. and Dean, RT. (1993). Does superoxide radical have a role in macropha mediated oxidative modification of LDL Atherosclerosis 99, 107-120. 

Sparrow, C.P., Parthasarathy, S. and Steinberg, D. (1988). Enzymatic modification of LDL by purified lipoxygenase plus phospholipase Ai mimics cell mediated oxidative modification. J. Lipid Res. 29, 745-733. 

Transition metal- or haem protein-mediated oxidative or reductive decomposition. 

Jessup, W., Darley-Usmar, V., O Leary, V. and Bidwell, S. (1991). 5-Lipoxygenase is not essential in the macrophage mediated oxidation of low density lipoprotein. Biochem. J. 278, 163-169. 

Dahlin, D.C., Miwa, G.T., Lu, A.Y.H. and Nelson, S.D. (1984). N-Acetyl-p-benzoquinone imine a cytochrome P-450-mediated oxidation product of acetaminophen. Proc. Natl Acad. Sci. USA 81, 1327-1331. 

Frenkel, K. (1992). Carcinogen-mediated oxidant formation and oxidative DNA damage. Pharmac. Ther. 53, 127-166. 

Kasprzak, K.S., Diwan, B.A., Rice, J.M., Misra, M., Riggs, C.W., Olinski, R and Dizdaroglu, M. (1992). Nickel(II)-mediated oxidative DNA base damage in renal and hepatic chromatin of pregnant rats and their fetuses. Possible relevance to carcinogenesis. Chem. Res. Tox. 5, 810-815. 

In their review some years ago, Reddy and Rao (1986) cited several lines of evidence for peroxisome-proliferation-mediated oxidative stress being associated with hepatocarcinogenesis. They mentioned the sustained increase in hydrogen peroxide production, the detectable increased levels of hydrogen peroxide in the livers of treated animals, increased lipid peroxidation associated with treatment and marked inhibition of hepatocarcinogenesis by antioxidant compounds. However, definitive studies remain to be carried out. 

Probucol, another di-r-butyl phenol, is an anti-atherosclerotic agent that can suppress the oxidation of low-density lipoprotein (LDL) in addition to lowering cholesterol levels. The antioxidant activity of probucol was measured, using EPR, with oxidation of methyl linoleate that was encapsulated in liposomal membranes or dissolved in hexane. Probucol suppressed ffee-radical-mediated oxidation. Its antioxidant activity was 17-fold less than that of tocopherol. This difference was less in liposomes than in hexane solution. Probucol suppressed the oxidation of LDL as efficiently as tocopherol. This work implies that physical factors as well as chemical reactivity are important in determining overall lipid peroxidation inhibition activity (Gotoh et al., 1992). 

Sakano, K. Inagaki, Y. Oikawa, S. Hiraku, Y. Kawanishi, S. Copper-mediated oxidative DNA damage induced by eugenol possible involvement of O-demethylation. Mutat. Res. 2004, 565, 35 44. 

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