Oxidation Of Sulfoxides Research Articles

A Low pKa Cysteine at the Active Site of Mouse Methionine Sulfoxide Reductase A

Methionine sulfoxide reductase A is an essential enzyme in the antioxidant system which scavenges reactive oxygen species through cyclic oxidation and reduction of methionine and methionine sulfoxide. Recently it has also been shown to catalyze the reverse reaction, oxidizing methionine residues to methionine sulfoxide. A cysteine at the active site of the enzyme is essential for both reductase and oxidase activities. This cysteine has been reported to have a pK(a) of 9.5 in the absence of substrate, decreasing to 5.7 upon binding of substrate. Using three independent methods, we show that the pK(a) of the active site cysteine of mouse methionine sulfoxide reductase is 7.2 even in the absence of substrate. The primary mechanism by which the pK(a) is lowered is hydrogen bonding of the active site Cys-72 to protonated Glu-115. The low pK(a) renders the active site cysteine susceptible to oxidation to sulfenic acid by micromolar concentrations of hydrogen peroxide. This characteristic supports a role for methionine sulfoxide reductase in redox signaling.

Chiral synthesis of indolizidines 209D and 167B via asymmetric oxidation of sulfides and sulfoxides

Chiral synthesis of indolizidine natural products (−)-209D and (−)-167B, as well as their antipodes, has been achieved through asymmetric oxidation of racemic thio-substituted indolizidines to the chiral sulfoxides and sulfones followed by Raney nickel reduction.

Kinetics and mechanism of electron-transfer reactions Oxidation of dimethyl sulfoxide by chroniium(VI) in acid perchlorate medium

Kinetics and mechanism of electron-transfer reactions Oxidation of dimethyl sulfoxide by chroniium(VI) in acid perchlorate medium

Effect of base nature on the oxidation of dimethyl sulfoxide with hydrogen peroxide in superbasic media

Kinetic relationships of the dimethyl sulfoxide oxidation to dimethyl sulfone with hydrogen peroxide in the presence of an alkali (MOH) or sodium tert-butoxide were investigated. Kinetic parameters of the process were calculated. The process was found to proceed through the intermediate formation of the alkaline salts MeOOH. The effect of the base nature on the stage of salt formation and oxidation was revealed.

PH-induced mechanistic changeover from hydroxyl radicals to iron(iv) in the Fenton reaction

A major pathway in the reaction between Fe(II) and H2O2 at pH 6–7 in non-coordinating buffers exhibits inverse kinetic dependence on [H+] and leads to oxidation of dimethyl sulfoxide (DMSO) to dimethyl sulfone (DMSO2). This step regenerates Fe(II) and makes the oxidation of DMSO catalytic, a finding that strongly supports Fe(IV) as a Fenton intermediate at near-neutral pH. This Fe(IV) is a less efficient oxidant for DMSO at pH 6–7 than is (H2O)5FeO2+, generated by ozone oxidation of Fe(H2O)62+, in acidic solutions. Large concentrations of DMSO are needed to achieve significant turnover numbers at pH ≥ 6 owing to the rapid competing reaction between Fe(II) and Fe(IV) that leads to irreversible loss of the catalyst. At pH 6 and ≤0.02 mM Fe(II), the ratio of apparent rate constants for the reactions of Fe(IV) with DMSO and with Fe(II) is ∼104. The results at pH 6–7 stand in stark contrast with those reported previously in acidic solutions where the Fenton reaction generates hydroxyl radicals. Under those conditions, DMSO is oxidized stoichiometrically to methylsulfinic acid and ethane. This path still plays a role (1–10%) at pH 6–7.

The Mechanism of Permanganate Oxidation of Sulfides and Sulfoxides

Coupled-cluster (CCSD) and density functional computations are used to investigate historically competing mechanisms for the permanganate oxidation of sulfides and sulfoxides. The calculations all lead to a mechanism of 1,3-dipolar cycloaddition of permanganate, as opposed to historical mechanisms of attack of the sulfur atom by one O or by Mn. Such a mechanism, reminiscent of ozonolysis, may prevail in most permanganate oxidations. The ab initio activation enthalpies are in reasonable agreement with the experimental data; the ab initio activation entropies are not, possibly because of problems with Eyring equation assumptions.

Gold‐Catalyzed Oxidative Cyclizations of 2‐Oxiranyl‐1‐alkynylbenzenes for Diastereoselective Synthesis of Highly Substituted 2‐Hydroxyindanones

AbstractWe report the gold‐catalyzed oxidative cyclizations of 2‐oxiranyl‐1‐alkynylbenzenes into highly substituted 2‐hydroxyindanone frameworks bearing a tertiary alcohol. Such gold‐catalyzed reactions comprise an initial internal redox reaction, sulfoxide oxidation of α‐carbonyl gold‐carbenoids, followed by gold‐catalyzed formal ene reactions on the resulting diketone intermediates.

ChemInform Abstract: Synthesis of Enantioenriched Sulfoxides

AbstractReview: 326 refs.

Influence of various compounds on electrostatic charging tendency in insulating oil

AbstractThe influence of various compounds on the increase of the electrostatic charging tendency (ECT) in insulating oil was investigated. Sulfide compounds, which are contained in new mineral oil, are identified for the first time as the original materials involved in the increase of the ECT. This is verified by heating tests of alkylbenzene with the addition of various compounds. Coexistence with copper and injection of oxygen enhance the increase of the ECT. Some sulfide and sulfoxide compounds increase the ECT markedly. On the other hand, the influence of sulfones, which are oxidation products of sulfoxides, is negligible. Although sulfonic acids, which are oxidation products of sulfones, markedly increase the ECT, the polarity is reverse. Thus, the ECT is influenced by the kinds and the molecular structures of additive sulfur compounds. The influence of nitrogen compounds and that of oxygen compounds are confirmed to be smaller than that of sulfur compounds. Since the amounts of nitrogen compounds and oxygen compounds are much smaller than those of sulfur compounds in mineral insulating oils, the influence of these compounds is considered negligible. Since the ECT of oils with the addition of sulfides or sulfoxides increases after heating, the other compounds should be created from these compounds that increase the ECT directly. Thus, the increase of the ECT is mostly caused by the oxidation of sulfides, which creates sulfoxides. Then certain compounds, which directly increase the ECT, are created from sulfoxides. If sulfones or sulfonic acids are created by the oxidation of sulfoxides, the ECT decreases because of the influence of these compounds on the ECT. It is most likely that some process other than oxidation occurs in the creation of the compounds that increase the ECT directly. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 176(3): 29–36, 2011; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21112

Synthesis of enantioenriched sulfoxides

This review discusses strategies for the asymmetric synthesis of sulfoxides, compounds with many applications in stereoselective synthesis and in some cases with pharmaceutical application. The review describes asymmetric oxidation, including metal catalyzed and nonmetal and biological oxidation processes, in addition to synthetic approaches via nucleophilic substitution of appropriately substituted precursors. Kinetic resolution in oxidation of sulfoxides to the analogous sulfones is also discussed; in certain instances, access to enantioenriched sulfoxides can be achieved via a combination of asymmetric sulfide oxidation and complementary kinetic resolution in sulfoxide oxidation.

Chemoselective Sulfide and Sulfoxide Oxidations by CpMo(CO)3Cl/HOOR: a DFT Mechanistic Study

The mechanism of sulfide and sulfoxide oxidation with peroxides (ROOH, R = H, Me), catalyzed by Mo(VI) complexes, was investigated by means of DFT/PBE1PBE calculations. Two different catalytic systems were considered: the first is based on the dioxocyclopentadienyl (Cp) complex CpMoO2Cl (Cp = η5-C5H5), also active as a catalyst for olefin epoxidation, and the second based on MoO2Cl2. The most favorable mechanism in the Cp system is initiated by the O−H activation of the HOOR oxidant, which in the presence of CpMoO2Cl leads to formation of CpMoO(OH)(OOR)Cl. Although this is the active species for olefin epoxidation, an alternative pathway with lower energy is available. With the crucial H-bond assistance of another oxidant molecule, the oxoperoxo complex CpMoO(O2)Cl forms, with release of alcohol ROH as byproduct and a calculated energy barrier below 25 kcal mol−1. The mechanisms unveiled for sulfide to sulfoxide oxidation and for sulfoxide to sulfone oxidation are equivalent in their general features and ...

Response to Comment on “Oxidation of Sulfoxides and Arsenic(III) in Corrosion of Nanoscale Zero Valent Iron by Oxygen: Evidence against Ferryl Ions (Fe(IV)) as Active Intermediates in Fenton Reaction”

Response to Comment on “Oxidation of Sulfoxides and Arsenic(III) in Corrosion of Nanoscale Zero Valent Iron by Oxygen: Evidence against Ferryl Ions (Fe(IV)) as Active Intermediates in Fenton Reaction”

Comment on “Oxidation of Sulfoxides and Arsenic(III) in Corrosion of Nanoscale Zero Valent Iron by Oxygen: Evidence against Ferryl Ions (Fe(IV)) as Active Intermediates in Fenton Reaction”

ADVERTISEMENT RETURN TO ISSUEPREVCorrespondence/Rebut...Correspondence/RebuttalNEXTComment on “Oxidation of Sulfoxides and Arsenic(III) in Corrosion of Nanoscale Zero Valent Iron by Oxygen: Evidence against Ferryl Ions (Fe(IV)) as Active Intermediates in Fenton Reaction”Christina K. Remucal†, Changha Lee‡, and David L. Sedlak§*View Author Information† Institute of Biogeochemistry and Pollutant Dynamics, Swiss Federal Institute of Technology (ETH), Zürich, Switzerland‡ School of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan, South Korea§ Department of Civil and Environmental Engineering, University of California at Berkeley, Berkeley, California 94720, United States*Phone: (510) 643-0256; fax: (510) 643-5264; e-mail: [email protected]Cite this: Environ. Sci. Technol. 2011, 45, 7, 3177–3178Publication Date (Web):March 4, 2011Publication History Published online4 March 2011Published inissue 1 April 2011https://doi.org/10.1021/es104399pCopyright © 2011 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views1456Altmetric-Citations14LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (662 KB) Get e-AlertsSUBJECTS:Alcohols,Aromatic compounds,Iron,Oxidation,Oxides Get e-Alerts

Oxidovanadium(V)-Catalyzed Kinetic Resolution of α-Hydroxy Ketones

Oxidovanadium complexes have previously been used for the oxidation and kinetic resolution of sulfides and sulfoxides, respectively. In 2005, Toste and co-workers demonstrated an efficient kinetic resolution of α-hydroxy acid derivatives catalyzed by an oxidovanadium complex (A. T. Radosevich, C. Musich, F. D. Toste J. Am. Chem. Soc. 2005, 127, 1090). The authors report a study of the vanadium-catalyzed kinetic resolution of α-hydroxy ketones. During this study several ligands are examined and various substituted benzoin adducts are investigated under optimized conditions, expanding the scope of vanadium-catalyzed kinetic resolutions.

Oxidation of Sulfoxides and Arsenic(III) in Corrosion of Nanoscale Zero Valent Iron by Oxygen: Evidence against Ferryl Ions (Fe(IV)) as Active Intermediates in Fenton Reaction

Previous studies have shown that the corrosion of zerovalent iron (ZVI) by oxygen (O(2)) via the Fenton reaction can lead to the oxidation of various organic and inorganic compounds. However, the nature of the oxidants involved (i.e., ferryl ion (Fe(IV)) versus hydroxyl radical (HO(•))) is still a controversial issue. In this work, we reevaluated the relative importance of these oxidants and their role in As(III) oxidation during the corrosion of nanoscale ZVI (nZVI) in air-saturated water. It was shown that Fe(IV) species could react with sulfoxides (e.g., dimethyl sulfoxide, methyl phenyl sulfoxide, and methyl p-tolyl sulfoxide) through a 2-electron transfer step producing corresponding sulfones, which markedly differed from their HO(•)-involved products. When using these sulfoxides as probe compounds, the formation of oxidation products indicative of HO(•) but no generation of sulfone products supporting Fe(IV) participation were observed in the nZVI/O(2) system over a wide pH range. As(III) could be completely or partially oxidized by nZVI in air-saturated water. Addition of scavengers for solution-phase HO(•) and/or Fe(IV) quenched As(III) oxidation at acidic pH but had little effect as solution pH increased, highlighting the importance of the heterogeneous iron surface reactions for As(III) oxidation at circumneutral pH.

Synthesis and stereoselective oxidation of α-thio-β-chloropropenyloxazolidin-2-ones

The investigation of the stereoselective reaction of α-thiopropanoyloxazolidin-2-ones with NCS to yield α-thio-β-chloropropenyloxazolidin-2-ones is described. Diastereoselective sulfur oxidation of the resulting α-thio-β-chloropropenyloxazolidin-2-ones shows modest diastereocontrol. However, via a combination of diastereoselective oxidation and subsequent kinetic resolution in the sulfoxide oxidation, diastereoselectivities of up to 94% de have been achieved.

An thin film of the di-decatungstosilicate with a tetra-ruthenium(IV)-oxo core and its electrochemical properties

A ruthenium-containing polyoxometalate Rb 8K 2[{Ru 4O 4(OH) 2(H 2O) 4}(γ-SiW 10O 36) 2]·25H 2O (RuSiW 10) with two redox-active centers of Ru and W was assembled on quartz, and ITO by the layer-by-layer self-assembly method. The regular assembled process was monitored by collecting UV–vis spectra of film after each bilayer recycle. The electrochemical properties were studied by cyclic voltammetry and hydrodynamic amperometry. The composite film showed electrocatalytic activity towards reduction of NO 2 - attributing to SiW 10 units, and oxidation of ascorbic acid, benzyl alcohol, and dimethyl sulfoxide (DMSO) arised from the Ru 4O 6 core. It may provide a novel material as bifunctional electrocatalyst for oxidation and reduction reactions, and amperometric sensor for the detection of NO 2 - and ascorbic acid.

ChemInform Abstract: Surface-Mediated Reactions. Part 8. Oxidation of Sulfides and Sulfoxides with tert-Butyl Hydroperoxide and OXONE.

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Dual Sites of Protein Initiation Control the Localization and Myristoylation of Methionine Sulfoxide Reductase A

Methionine sulfoxide reductase A is an essential enzyme in the antioxidant system, which scavenges reactive oxygen species through cyclic oxidation and reduction of methionine and methionine sulfoxide. In mammals, one gene encodes two forms of the reductase, one targeted to the cytosol and the other to mitochondria. The cytosolic form displays faster mobility than the mitochondrial form, suggesting a lower molecular weight for the former. The apparent size difference and targeting to two cellular compartments had been proposed to result from differential splicing of mRNA. We now show that differential targeting is effected by use of two initiation sites, one of which includes a mitochondrial targeting sequence, whereas the other does not. We also demonstrate that the mass of the cytosolic form is not less than that of the mitochondrial form; the faster mobility of cytosolic form is due to its myristoylation. Lipidation of methionine sulfoxide reductase A occurs in the mouse, in transfected tissue culture cells, and even in a cell-free protein synthesis system. The physiologic role of myristoylation of MsrA remains to be elucidated.

Suppression of increase in electrostatic charging tendency of insulating oil by aging used for power transformer insulation

Additives to insulating oil and oil treatment by absorbents are investigated by thermal aging tests with the aim of suppressing flow electrification in power transformer insulation. 1, 2, 3-benzotriazol (BTA) is found to be effective for suppressing the increase of electrostatic charging tendency (ECT) in oils that contain either sulfide or sulfoxide compounds. Sulfide compounds are contained in new oil while sulfoxide compounds are generated by the oxidation of sulfide compounds. However, 2, 6-ditertiary-butyl paracresol (DBPC) is only effective for oils that contain sulfide compounds. The addition of sulfoxide compounds significantly increases the ECT of DBPC-added oil by the thermal aging tests. DBPC can suppress the conversion of sulfide to sulfoxide by blocking the generation of peroxide. However, DBPC has negligible effect on suppressing the increase in ECT by sulfonium ions, which are generated by the oxidation of sulfoxide. Negatively charged BTA ions, which are generated by the dissociation of hydrogen ions from BTA molecules, can mitigate the increase in ECT by sulfonium ions, which charge insulating oil positively. The effect of BTA is found to be lost when the concentration in oil decreases due to the adsorption on solid insulators. Oil treatment by absorbents such as clay, activated carbon and silica gel is found to remarkably decrease the ECT of deteriorated oil. However, additional thermal aging test increases the ECT to the same level as before the oil treatment. Although the additives and the oil treatment by absorbents are effective for suppressing and decreasing the ECT of insulating oils, their long-term effect is not assured. Thus periodical measurements of the ECT of insulating oils are crucial for the sake of preventive maintenance of aged transformers.