1
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Sugiyama K, Sakurai R, Sato F, Watanabe K, Fujimura T, Sato K. Fluorescence Quenching Effect of a Highly Active Nitroxyl Radical on 7-amino-4-methylcoumarin and Glutathione Sensing. J Fluoresc 2024:10.1007/s10895-024-03833-3. [PMID: 39028447 DOI: 10.1007/s10895-024-03833-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2024] [Accepted: 07/03/2024] [Indexed: 07/20/2024]
Abstract
Nitroxyl radical compounds, such as 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), are stable radical compounds with a variety of unique characteristics, including fluorescence quenching. In this study, we investigated the fluorescence quenching effect of nortropine N-oxyl (NNO), which is a highly active nitroxyl radical that is more active than TEMPO in oxidation catalysis. The fluorescence intensity of 7-amino-4-methylcoumarin (AMC) was quenched by NNO and TEMPO to 5% and 95% of the initial fluorescence intensity, respectively, indicating highly efficient quenching by NNO. In addition, we used this reaction to measure glutathione concentration. The quenching effect of NNO was abrogated by the chemical reaction with glutathione, resulting in restoration of AMC fluorescence. This response was observed at glutathione concentrations from 10 µM to 1 mM, and good calibration curves were obtained from 10 to 250 µM.
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Affiliation(s)
- Kyoko Sugiyama
- Faculty of Pharmaceutical Science, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba, Sendai, Miyagi, 981-8558, Japan
| | - Rin Sakurai
- Faculty of Pharmaceutical Science, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba, Sendai, Miyagi, 981-8558, Japan
| | - Fumiya Sato
- Faculty of Pharmaceutical Science, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba, Sendai, Miyagi, 981-8558, Japan
| | - Kazuhiro Watanabe
- Faculty of Pharmaceutical Science, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba, Sendai, Miyagi, 981-8558, Japan
| | - Tsutomu Fujimura
- Faculty of Pharmaceutical Science, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba, Sendai, Miyagi, 981-8558, Japan
| | - Katsuhiko Sato
- Faculty of Pharmaceutical Science, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba, Sendai, Miyagi, 981-8558, Japan.
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2
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Bray JM, Stephens SM, Weierbach SM, Vargas K, Lambert KM. Recent advancements in the use of Bobbitt's salt and 4-acetamidoTEMPO. Chem Commun (Camb) 2023; 59:14063-14092. [PMID: 37946555 DOI: 10.1039/d3cc04709a] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2023]
Abstract
Recent advances in synthetic methodologies for selective, oxidative transformations using Bobbitt's salt (4-acetamido-2,2,6,6-tetramethyl-1-oxopiperidinium tetrafluoroborate, 1) and its stable organic nitroxide counterpart ACT (4-acetamidoTEMPO, 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxyl, 2) have led to increased applications across a broad array of disciplines. Current applications and mechanistic understanding of these metal-free, environmentally benign, and easily accessible organic oxidants now span well-beyond the seminal use of 1 and 2 in selective alcohol oxidations. New synthetic methodologies for the oxidation of alcohols, ethers, amines, thiols, C-H bonds and other functional groups with 1 and 2 along with the field's current mechanistic understandings of these processes are presented alongside our contributions in this area. Exciting new areas harnessing the unique properties of these oxidants include: applications to drug discovery and natural product total synthesis, the development of new electrocatalytic methods for depolymerization of lignin and modification of other biopolymers, in vitro and in vivo nucleoside modifications, applications in supramolecular catalysis, the synthesis of new polymers and materials, enhancements in the design of organic redox flow batteries, uses in organic fuel cells, applications and advancements in energy storage, the development of electrochemical sensors, and the production of renewable fuels.
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Affiliation(s)
- Jean M Bray
- Department of Chemistry and Biochemistry, Old Dominion University, 4501 Elkhorn Ave, Norfolk, VA 23529, USA.
| | - Shannon M Stephens
- Department of Chemistry and Biochemistry, Old Dominion University, 4501 Elkhorn Ave, Norfolk, VA 23529, USA.
| | - Shayne M Weierbach
- Department of Chemistry and Biochemistry, Old Dominion University, 4501 Elkhorn Ave, Norfolk, VA 23529, USA.
| | - Karen Vargas
- Department of Chemistry and Biochemistry, Old Dominion University, 4501 Elkhorn Ave, Norfolk, VA 23529, USA.
| | - Kyle M Lambert
- Department of Chemistry and Biochemistry, Old Dominion University, 4501 Elkhorn Ave, Norfolk, VA 23529, USA.
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3
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Ono T, Sato F, Kumano M, Komatsu S, Sugiyama K, Watanabe K, Yoshida K, Sasano Y, Fujimura T, Iwabuchi Y, Kashiwagi Y, Sato K. Determination of antibiotics by amperometry using nortropine N-oxyl, a highly active nitroxyl radical. ANAL SCI 2023; 39:1771-1775. [PMID: 37378820 DOI: 10.1007/s44211-023-00388-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 06/14/2023] [Indexed: 06/29/2023]
Abstract
Nitroxyl radical compounds oxidize hydroxy groups and some amino groups upon application of an electric potential. The resulting anodic current depends on the concentration of these functional groups in solution. Thus, it is possible to quantify compounds containing these functional groups by electrochemical methods. Cyclic voltammetry has been used to evaluate the catalytic activity of nitroxyl radicals, and the ability of such radicals to sense biological and other compounds. In this study, we evaluated a method for quantifying compounds using constant-potential electrolysis (amperometry) of nitroxyl radicals for application in flow injection analysis and high-performance liquid chromatography as an electrochemical detector. When amperometry was performed using 2,2,6,6-tetramethylpiperidine 1-oxyl, a common nitroxyl radical compound, little change was observed even with 100 mM glucose due to its low reactivity in neutral aqueous solutions. In contrast, 2-azaadamantane N-oxyl and nortropine N-oxyl, which are highly active nitroxyl radicals, showed a concentration-dependent response in neutral aqueous solution. Responses of 33.8 and 125.9 μA, respectively, were observed. By recognition of hydroxy and amino groups, we have succeeded in the electrochemical detection of some drugs by amperometry. Streptomycin, an aminoglycoside antibiotic, was quantifiable in the range of 30-1000 µM.
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Affiliation(s)
- Tetsuya Ono
- School of Pharmaceutical Sciences, Ohu University, 31-1 Misumido, Tomita-machi, Koriyama, Fukushima, 963-8611, Japan.
| | - Fumiya Sato
- Faculty of Pharmaceutical Science, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba, Sendai, Miyagi, 981-8558, Japan
| | - Masayuki Kumano
- Faculty of Pharmaceutical Science, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba, Sendai, Miyagi, 981-8558, Japan
| | - Sachiko Komatsu
- Faculty of Pharmaceutical Science, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba, Sendai, Miyagi, 981-8558, Japan
| | - Kyoko Sugiyama
- Faculty of Pharmaceutical Science, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba, Sendai, Miyagi, 981-8558, Japan
| | - Kazuhiro Watanabe
- Faculty of Pharmaceutical Science, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba, Sendai, Miyagi, 981-8558, Japan
| | - Kentaro Yoshida
- School of Pharmaceutical Sciences, Ohu University, 31-1 Misumido, Tomita-machi, Koriyama, Fukushima, 963-8611, Japan
| | - Yusuke Sasano
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan
| | - Tsutomu Fujimura
- Faculty of Pharmaceutical Science, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba, Sendai, Miyagi, 981-8558, Japan
| | - Yoshiharu Iwabuchi
- Graduate School of Pharmaceutical Sciences, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, 980-8578, Japan
| | - Yoshitomo Kashiwagi
- School of Pharmaceutical Sciences, Ohu University, 31-1 Misumido, Tomita-machi, Koriyama, Fukushima, 963-8611, Japan
| | - Katsuhiko Sato
- Faculty of Pharmaceutical Science, Tohoku Medical and Pharmaceutical University, 4-4-1 Komatsushima, Aoba, Sendai, Miyagi, 981-8558, Japan.
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4
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Abstract
Nitroxides, also known as nitroxyl radicals, are long-lived or stable radicals with the general structure R1R2N-O•. The spin distribution over the nitroxide N and O atoms contributes to the thermodynamic stability of these radicals. The presence of bulky N-substituents R1 and R2 prevents nitroxide radical dimerization, ensuring their kinetic stability. Despite their reactivity toward various transient C radicals, some nitroxides can be easily stored under air at room temperature. Furthermore, nitroxides can be oxidized to oxoammonium salts (R1R2N═O+) or reduced to anions (R1R2N-O-), enabling them to act as valuable oxidants or reductants depending on their oxidation state. Therefore, they exhibit interesting reactivity across all three oxidation states. Due to these fascinating properties, nitroxides find extensive applications in diverse fields such as biochemistry, medicinal chemistry, materials science, and organic synthesis. This review focuses on the versatile applications of nitroxides in organic synthesis. For their use in other important fields, we will refer to several review articles. The introductory part provides a brief overview of the history of nitroxide chemistry. Subsequently, the key methods for preparing nitroxides are discussed, followed by an examination of their structural diversity and physical properties. The main portion of this review is dedicated to oxidation reactions, wherein parent nitroxides or their corresponding oxoammonium salts serve as active species. It will be demonstrated that various functional groups (such as alcohols, amines, enolates, and alkanes among others) can be efficiently oxidized. These oxidations can be carried out using nitroxides as catalysts in combination with various stoichiometric terminal oxidants. By reducing nitroxides to their corresponding anions, they become effective reducing reagents with intriguing applications in organic synthesis. Nitroxides possess the ability to selectively react with transient radicals, making them useful for terminating radical cascade reactions by forming alkoxyamines. Depending on their structure, alkoxyamines exhibit weak C-O bonds, allowing for the thermal generation of C radicals through reversible C-O bond cleavage. Such thermally generated C radicals can participate in various radical transformations, as discussed toward the end of this review. Furthermore, the application of this strategy in natural product synthesis will be presented.
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Affiliation(s)
- Dirk Leifert
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149 Münster, Germany
| | - Armido Studer
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149 Münster, Germany
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5
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Weierbach SM, Reynolds RP, Stephens SM, Vlasakakis KV, Ritter RT, White OM, Patel NH, Hayes EC, Dunmire S, Lambert KM. Chemoselective Oxidation of Thiols with Oxoammonium Cations. J Org Chem 2023; 88:11392-11410. [PMID: 35926190 DOI: 10.1021/acs.joc.2c01097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The oxidation of various aryl and aliphatic thiols with the commercially available and environmentally benign reagent Bobbitt's salt (1) has been investigated. The reaction affords the corresponding disulfide products in good to excellent yields (71-99%) and can be accomplished in water, methanol, or acetonitrile solvent. Moreover, the process is highly chemoselective, tolerating traditionally oxidation-labile groups such as free amines and alcohols. Combined experimental and computational studies reveal that the oxidation takes place via a polar two-electron process with concomitant and unexpected deoxygenation of the oxoammonium cation through homolysis of the weak N-O bond, differing from prototypical radical-based thiol couplings. This unusual consumption of the oxidant has significant implications for the development of new nitroxide-based radical traps for probing S-centered radicals, the advancement of new electrochemical or catalytic processes involving nitroxide/oxoammonium salt redox couples, and applications to biological systems.
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Affiliation(s)
- Shayne M Weierbach
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia 23529, United States
| | - Robert P Reynolds
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia 23529, United States
| | - Shannon M Stephens
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia 23529, United States
| | - Kostantinos V Vlasakakis
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia 23529, United States
| | - Ramsey T Ritter
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia 23529, United States
| | - Olivia M White
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia 23529, United States
| | - Nishi H Patel
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia 23529, United States
| | - Eric C Hayes
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia 23529, United States
| | - Sydney Dunmire
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia 23529, United States
| | - Kyle M Lambert
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia 23529, United States
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6
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Lewis SG, Dadum AG, McLean D, Buenavista J, Myers J, Lambert KM, Fair JD. Chemoselective Oxidation of Alcohols in the Presence of Amines Using an Oxoammonium Salt. Tetrahedron 2023; 131:133226. [PMID: 36742269 PMCID: PMC9894077 DOI: 10.1016/j.tet.2022.133226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The oxidation of alcohols in the presence of reactive amines employing the commercially available oxoammonium cation, "Bobbitt's salt" is described. The oxidation is accomplished under acidic conditions and subsequent treatment with a suitable base affords a convenient one-pot method to access imines in good to excellent isolated yields (74-99%).
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Affiliation(s)
- Stephonda G. Lewis
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia, 23529, United States
| | - Abra G. Dadum
- Maida Department of Chemistry, Biochemistry, Physics and Engineering, Indiana University of Pennsylvania, Indiana, Pennsylvania 15705, United States
| | - David McLean
- Maida Department of Chemistry, Biochemistry, Physics and Engineering, Indiana University of Pennsylvania, Indiana, Pennsylvania 15705, United States
| | - Jhennalin Buenavista
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia, 23529, United States
| | - Jaileen Myers
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia, 23529, United States
| | - Kyle M. Lambert
- Department of Chemistry and Biochemistry, Old Dominion University, Norfolk, Virginia, 23529, United States
| | - Justin D. Fair
- Maida Department of Chemistry, Biochemistry, Physics and Engineering, Indiana University of Pennsylvania, Indiana, Pennsylvania 15705, United States
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7
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Fast, easy oxidation of alcohols using an oxoammonium salt bearing the nitrate anion. Tetrahedron Lett 2022. [DOI: 10.1016/j.tetlet.2022.154332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
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8
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Chen F, Tang Y, Li X, Duan Y, Chen C, Zheng Y. Oxoammonium Salt‐Mediated Vicinal Oxyazidation of Alkenes with NaN
3
: Access to
β
‐Aminooxy Azides. Adv Synth Catal 2021. [DOI: 10.1002/adsc.202100783] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Fei Chen
- Henan Provincial Engineering and Technology Research Center for Precise Synthesis of Fluorine-Containing Drugs, College of Chemistry and Chemical Engineering Anyang Normal University Anyang 455000 People's Republic of China
| | - Yu‐Ting Tang
- Henan Provincial Engineering and Technology Research Center for Precise Synthesis of Fluorine-Containing Drugs, College of Chemistry and Chemical Engineering Anyang Normal University Anyang 455000 People's Republic of China
| | - Xin‐Ru Li
- Henan Provincial Engineering and Technology Research Center for Precise Synthesis of Fluorine-Containing Drugs, College of Chemistry and Chemical Engineering Anyang Normal University Anyang 455000 People's Republic of China
| | - Yan‐Yan Duan
- Henan Provincial Engineering and Technology Research Center for Precise Synthesis of Fluorine-Containing Drugs, College of Chemistry and Chemical Engineering Anyang Normal University Anyang 455000 People's Republic of China
| | - Chao‐Xing Chen
- Henan Provincial Engineering and Technology Research Center for Precise Synthesis of Fluorine-Containing Drugs, College of Chemistry and Chemical Engineering Anyang Normal University Anyang 455000 People's Republic of China
| | - Yang Zheng
- Henan Provincial Engineering and Technology Research Center for Precise Synthesis of Fluorine-Containing Drugs, College of Chemistry and Chemical Engineering Anyang Normal University Anyang 455000 People's Republic of China
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9
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Meador RIL, Anderson RE, Chisholm JD. Tandem elimination-oxidation of tertiary benzylic alcohols with an oxoammonium salt. Org Biomol Chem 2021; 19:6233-6236. [PMID: 34231623 DOI: 10.1039/d1ob00965f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Tertiary benzylic alcohols react with oxoammonium salts, undergoing a tandem elimination/allylic oxidation to provide an allylic ether product in a single step. This mode of reactivity provides a rapid entry into allylic ethers from certain benzylic tertiary alcohols. The allylic ether may be cleaved under reductive conditions to reveal the allylic alcohol.
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Affiliation(s)
- Rowan I L Meador
- Department of Chemistry, Syracuse University, 1-014 Center for Science and Technology, Syracuse, NY 13244, USA.
| | - Robert E Anderson
- Department of Chemistry, Syracuse University, 1-014 Center for Science and Technology, Syracuse, NY 13244, USA.
| | - John D Chisholm
- Department of Chemistry, Syracuse University, 1-014 Center for Science and Technology, Syracuse, NY 13244, USA.
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10
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Wang M, Xiang Q, Si W, Song R, Yang D, Li M, Lv J. Bioinspired cyclization of in situ generated γ-indolyl β,γ-unsaturated α-keto esters via an oxidative enamine process: facile approaches to pyrano[2,3- b]indoles. Org Chem Front 2021. [DOI: 10.1039/d1qo00996f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
A bioinspired cyclization of in situ generated γ-indolyl β,γ-unsaturated α-ketoesters with an oxoammonium salt via an oxidative enamine process has been developed.
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Affiliation(s)
- Man Wang
- Key Laboratory of Optic-electric Sensing and Analytic Chemistry for Life Science, MOE, College of Chemistry and Molecular Engineering, Qingdao University of Science & Technology, Qingdao 266042, China
| | - Qirui Xiang
- Key Laboratory of Optic-electric Sensing and Analytic Chemistry for Life Science, MOE, College of Chemistry and Molecular Engineering, Qingdao University of Science & Technology, Qingdao 266042, China
| | - Wen Si
- Key Laboratory of Optic-electric Sensing and Analytic Chemistry for Life Science, MOE, College of Chemistry and Molecular Engineering, Qingdao University of Science & Technology, Qingdao 266042, China
| | - Ran Song
- Key Laboratory of Optic-electric Sensing and Analytic Chemistry for Life Science, MOE, College of Chemistry and Molecular Engineering, Qingdao University of Science & Technology, Qingdao 266042, China
| | - Daoshan Yang
- Key Laboratory of Optic-electric Sensing and Analytic Chemistry for Life Science, MOE, College of Chemistry and Molecular Engineering, Qingdao University of Science & Technology, Qingdao 266042, China
| | - Ming Li
- Key Laboratory of Optic-electric Sensing and Analytic Chemistry for Life Science, MOE, College of Chemistry and Molecular Engineering, Qingdao University of Science & Technology, Qingdao 266042, China
| | - Jian Lv
- Key Laboratory of Optic-electric Sensing and Analytic Chemistry for Life Science, MOE, College of Chemistry and Molecular Engineering, Qingdao University of Science & Technology, Qingdao 266042, China
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11
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Stoyanovsky AD, Stoyanovsky DA. 1-Oxo-2,2,6,6-tetramethylpiperidinium bromide converts α-H N,N-dialkylhydroxylamines to nitrones via a two-electron oxidation mechanism. Sci Rep 2018; 8:15323. [PMID: 30333514 PMCID: PMC6193029 DOI: 10.1038/s41598-018-33639-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2018] [Accepted: 10/02/2018] [Indexed: 01/13/2023] Open
Abstract
Herein we provide experimental proof that 1-oxo-2,2,6,6-tetramethylpiperidinium bromide converts α-H N,N-dialkylhydroxylamines to nitrones via a two-electron oxidation mechanism. The reactions reported are rapid, proceed under mild conditions, and afford nitrones in excellent yields.
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Affiliation(s)
| | - Detcho A Stoyanovsky
- Department of Environmental and Occupational Health, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
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12
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Tiwari V, Badavath VN, Singh AK, Kandasamy J. A highly efficient TEMPO mediated oxidation of sugar primary alcohols into uronic acids using 1-chloro-1,2-benziodoxol-3(1H)-one at room temperature. Tetrahedron Lett 2018. [DOI: 10.1016/j.tetlet.2018.05.021] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
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13
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Gerken JB, Pang YQ, Lauber MB, Stahl SS. Structural Effects on the pH-Dependent Redox Properties of Organic Nitroxyls: Pourbaix Diagrams for TEMPO, ABNO, and Three TEMPO Analogs. J Org Chem 2017; 83:7323-7330. [PMID: 29182282 DOI: 10.1021/acs.joc.7b02547] [Citation(s) in RCA: 56] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Electrochemical studies of the reduction and oxidation reactions of five different organic nitroxyls have been performed across a wide pH range (0-13). The resulting Pourbaix diagrams illustrate structural effects on their various redox potentials and on the p Ka values of the corresponding hydroxylamine and hydroxylammonium ions. Evidence is also given for the reversible formation of a hydroxylamine N-oxide when nitroxyls are oxidized in alkaline media. Structural effects on the thermodynamics of this reaction are assessed.
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Affiliation(s)
- James B Gerken
- Department of Chemistry , University of Wisconsin - Madison , 1101 University Avenue , Madison , Wisconsin 53706-1322 , United States
| | - Yutong Q Pang
- Department of Chemistry , University of Wisconsin - Madison , 1101 University Avenue , Madison , Wisconsin 53706-1322 , United States
| | - Markus B Lauber
- Department of Chemistry , University of Wisconsin - Madison , 1101 University Avenue , Madison , Wisconsin 53706-1322 , United States
| | - Shannon S Stahl
- Department of Chemistry , University of Wisconsin - Madison , 1101 University Avenue , Madison , Wisconsin 53706-1322 , United States
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