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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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2
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Wang Z, Niu K, Liu Y, Song H, Wang Q. Electrochemical α-C(sp 3)-H/O-H cross-coupling of isochromans and alcohols assisted by benzoic acid. Chem Commun (Camb) 2022; 58:10949-10952. [PMID: 36082778 DOI: 10.1039/d2cc03883h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Isochroman moieties are present in a wide variety of biologically active molecules, but converting isochromans to α-substituted derivatives under mild conditions is challenging. Herein, we report a mild, convenient protocol for synthesis of α-alkoxy isochroman derivatives by means of electrochemical α-C(sp3)-H/O-H cross-coupling reactions of isochromans and alcohols in the presence of benzoic acid, which facilitated the electro-oxidation process and increased the product yield. Various alcohols and isochromans, as well as other structurally similar substrates, gave moderate to high yields of the desired coupling products, and the reaction could be carried out on a gram scale.
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Affiliation(s)
- Zhuang Wang
- State Key Laboratory of Elemento-Organic Chemistry, Research Institute of Elemento-Organic Chemistry, College of Chemistry, Frontiers Science Center for New Organic Matter, Nankai University, Tianjin, 300071, People's Republic of China.
| | - Kaikai Niu
- State Key Laboratory of Elemento-Organic Chemistry, Research Institute of Elemento-Organic Chemistry, College of Chemistry, Frontiers Science Center for New Organic Matter, Nankai University, Tianjin, 300071, People's Republic of China.
| | - Yuxiu Liu
- State Key Laboratory of Elemento-Organic Chemistry, Research Institute of Elemento-Organic Chemistry, College of Chemistry, Frontiers Science Center for New Organic Matter, Nankai University, Tianjin, 300071, People's Republic of China.
| | - Hongjian Song
- State Key Laboratory of Elemento-Organic Chemistry, Research Institute of Elemento-Organic Chemistry, College of Chemistry, Frontiers Science Center for New Organic Matter, Nankai University, Tianjin, 300071, People's Republic of China.
| | - Qingmin Wang
- State Key Laboratory of Elemento-Organic Chemistry, Research Institute of Elemento-Organic Chemistry, College of Chemistry, Frontiers Science Center for New Organic Matter, Nankai University, Tianjin, 300071, People's Republic of China.
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3
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Zhu S, Wang BB, Tan MC, Qian X, Ying S, Liu Y, Li C, Jin Z, Jiang H, Gui QW. Ultrasound Accelerated Expedient and Eco-Friendly Synthesis of Aryl
Sulfonates Using I2 As Catalyst At Ambient Conditions. LETT ORG CHEM 2022. [DOI: 10.2174/1570178618666210929124259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
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Aryl sulfonates were developed by ssing an energy-saving and eco-friendly
approach, through ultrasound-assisted coupling reaction of readily sodium sulfinates with
N-hydroxyphthalimide, under metal-free and mild conditions within 10 min at room temperature.
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Affiliation(s)
- Sha Zhu
- College of Chemistry and Materials Science, Hunan Agricultural University, Changsha, 410128, P.R. China
| | - Bin-Bin Wang
- College of Chemistry and Materials Science, Hunan Agricultural University, Changsha, 410128, P.R. China
| | - Mei-Chen Tan
- College of Chemistry and Materials Science, Hunan Agricultural University, Changsha, 410128, P.R. China
| | - Xiaofu Qian
- College of Chemistry and Materials Science, Hunan Agricultural University, Changsha, 410128, P.R. China
| | - Shengneng Ying
- College of Chemistry and Materials Science, Hunan Agricultural University, Changsha, 410128, P.R. China
| | - Yang Liu
- College of Chemistry and Materials Science, Hunan Agricultural University, Changsha, 410128, P.R. China
| | - Cehua Li
- College of Chemistry and Materials Science, Hunan Agricultural University, Changsha, 410128, P.R. China
| | - Zheng Jin
- College of Chemistry and Materials Science, Hunan Agricultural University, Changsha, 410128, P.R. China
| | - Hongmei Jiang
- College of Chemistry and Materials Science, Hunan Agricultural University, Changsha, 410128, P.R. China
| | - Qing-Wen Gui
- College of Chemistry and Materials Science, Hunan Agricultural University, Changsha, 410128, P.R. China
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Tretyakov EV, Ovcharenko VI, Terent'ev AO, Krylov IB, Magdesieva TV, Mazhukin DG, Gritsan NP. Conjugated nitroxide radicals. RUSSIAN CHEMICAL REVIEWS 2022. [DOI: 10.1070/rcr5025] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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Khalili D, Roosta M, Khalafi-Nezhad A, Ebrahimi E. From methylarenes to Esters: Efficient oxidative Csp3-H activation promoted by CuO decorated magnetic reduced graphene oxide. NEW J CHEM 2022. [DOI: 10.1039/d2nj00728b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Magnetic reduced graphene oxide supported CuO (rGO/Fe3O4-CuO) as the heterogeneous catalyst in cross dehydrogenative coupling (CDC) reactions has been demonstrated for the synthesis of esters using methyl aromatics, aldehydes/benzyl alcohols...
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Batra A, Singh P, Singh KN. Latest Advancements in Transition‐Metal‐Free Carbon‐Heteroatom Bond Formation Reactions
via
Cross‐ Dehydrogenative Coupling. ASIAN J ORG CHEM 2021. [DOI: 10.1002/ajoc.202100070] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Aanchal Batra
- PG Department of Chemistry Mehr Chand Mahajan DAV College for Women, Sec 36/A Chandigarh 160036 India
| | | | - Kamal Nain Singh
- Department of Chemistry and Centre of Advanced studies in Chemistry Panjab University Chandigarh 160014 India
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Jiang H, Tang X, Liu S, Wang L, Shen H, Yang J, Wang H, Gui QW. Ultrasound accelerated synthesis of O-alkylated hydroximides under solvent- and metal-free conditions. Org Biomol Chem 2019; 17:10223-10227. [PMID: 31777898 DOI: 10.1039/c9ob02245g] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A novel, sustainable, environmentally friendly, high substrate scope, efficient, solvent-free and metal catalyst-free method for the cross-dehydrogenative coupling (CDC) reaction between N-hydroxyphthalimide (NHPI) and benzyl/ether compounds is described. This coupling reaction proceeds through ultrasound acceleration. Compared to conventional heating conditions, the use of ultrasound techniques not only improves the reaction efficiency and enhances the reaction rate but also minimizes the side reactions.
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Affiliation(s)
- Hongmei Jiang
- College of Science, Hunan Agricultural University, Changsha 410128, People's Republic of China. and State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemical Engineering, Hunan University, Changsha 410082, People's Republic of China
| | - Xiaoyue Tang
- Department of Pharmaceutical Engineering, School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou 510640, People's Republic of China
| | - Sihan Liu
- College of Science, Hunan Agricultural University, Changsha 410128, People's Republic of China.
| | - Lian Wang
- College of Science, Hunan Agricultural University, Changsha 410128, People's Republic of China.
| | - Haicheng Shen
- College of Science, Hunan Agricultural University, Changsha 410128, People's Republic of China.
| | - Jiankui Yang
- College of Science, Hunan Agricultural University, Changsha 410128, People's Republic of China.
| | - Huixian Wang
- College of Science, Hunan Agricultural University, Changsha 410128, People's Republic of China.
| | - Qing-Wen Gui
- College of Science, Hunan Agricultural University, Changsha 410128, People's Republic of China.
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