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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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Harth E, Keyes A, Dau H, Matyjaszewski K. Tandem Living Insertion and Controlled Radical Polymerization for Polyolefin-Polyvinyl Block Copolymers. Angew Chem Int Ed Engl 2021; 61:e202112742. [PMID: 34967088 DOI: 10.1002/anie.202112742] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2021] [Indexed: 11/07/2022]
Abstract
Practical synthesis of polyolefin-polyvinyl block copolymers remains a challenge for transition-metal catalyzed polymerizations. Common approaches functionalize polyolefins for post-radical polymerization via insertion methods, yet sacrifice the livingness of the olefin polymerization. This work identifies an orthogonal radical/spin coupling technique which affords tandem living insertion and controlled radical polymerization. The broad tolerance of this coupling technique has been demonstrated for diverse radical/spin traps such as 2,2,5-trimethyl-4-phenyl-3-azahexane-3-nitroxide (TIPNO), 1-oxyl- (2,2,6,6-tetramethylpiperidine) -4-yl-α-bromoisobutyrate (TEMPO-Br), and N-tert -butyl-α-phenylnitrone (PBN). Subsequent controlled radical polymerization is demonstrated with NMP and atom transfer radical polymerization (ATRP), yielding polyolefin-polyvinyl di- and triblock copolymers ( Đ <1.3) with acrylic, vinylic and styrenic segments. These findings highlight radical trapping as an approach to expand the scope of polyolefin functionalization techniques to access polyolefin macroinitiators.
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Affiliation(s)
- Eva Harth
- University of Houston, Chemistry, 406 STL Building, United States, 77004, Houston, UNITED STATES
| | | | - Huong Dau
- University of Houston, Chemistry, UNITED STATES
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Harth E, Keyes A, Dau H, Matyjaszewski K. Tandem Living Insertion and Controlled Radical Polymerization for Polyolefin‐Polyvinyl Block Copolymers. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202112742] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Eva Harth
- University of Houston Chemistry 406 STL BuildingUnited States 77004 Houston UNITED STATES
| | | | - Huong Dau
- University of Houston Chemistry UNITED STATES
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Menendez Rodriguez G, Díaz-Requejo MM, Pérez PJ. Metal-Catalyzed Postpolymerization Strategies for Polar Group Incorporation into Polyolefins Containing C–C, C═C, and Aromatic Rings. Macromolecules 2021. [DOI: 10.1021/acs.macromol.1c00374] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Gabriel Menendez Rodriguez
- Laboratorio de Catálisis Homogénea, Departamento de Química y Ciencia de los Materiales, Unidad Asociada al CSIC, Centro de Investigación en Química Sostenible (CIQSO), Campus de El Carmen s/n, Universidad de Huelva, 21007 Huelva, Spain
| | - M. Mar Díaz-Requejo
- Laboratorio de Catálisis Homogénea, Departamento de Química y Ciencia de los Materiales, Unidad Asociada al CSIC, Centro de Investigación en Química Sostenible (CIQSO), Campus de El Carmen s/n, Universidad de Huelva, 21007 Huelva, Spain
| | - Pedro J. Pérez
- Laboratorio de Catálisis Homogénea, Departamento de Química y Ciencia de los Materiales, Unidad Asociada al CSIC, Centro de Investigación en Química Sostenible (CIQSO), Campus de El Carmen s/n, Universidad de Huelva, 21007 Huelva, Spain
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Qu Y, Chang X, Chen S, Zhang W. In situ synthesis of thermoresponsive 4-arm star block copolymer nano-assemblies by dispersion RAFT polymerization. Polym Chem 2017. [DOI: 10.1039/c7py00508c] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Thermoresponsive 4-arm star block copolymer nano-assemblies were synthesized, and their interesting thermoresponse was investigated.
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Affiliation(s)
- Yaqing Qu
- Key Laboratory of Functional Polymer Materials of the Ministry of Education
- Institute of Polymer Chemistry
- College of Chemistry
- Nankai University
- Tianjin 300071
| | - Xueying Chang
- Key Laboratory of Functional Polymer Materials of the Ministry of Education
- Institute of Polymer Chemistry
- College of Chemistry
- Nankai University
- Tianjin 300071
| | - Shengli Chen
- Key Laboratory of Functional Polymer Materials of the Ministry of Education
- Institute of Polymer Chemistry
- College of Chemistry
- Nankai University
- Tianjin 300071
| | - Wangqing Zhang
- Key Laboratory of Functional Polymer Materials of the Ministry of Education
- Institute of Polymer Chemistry
- College of Chemistry
- Nankai University
- Tianjin 300071
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Ren JM, McKenzie TG, Fu Q, Wong EHH, Xu J, An Z, Shanmugam S, Davis TP, Boyer C, Qiao GG. Star Polymers. Chem Rev 2016; 116:6743-836. [PMID: 27299693 DOI: 10.1021/acs.chemrev.6b00008] [Citation(s) in RCA: 525] [Impact Index Per Article: 65.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Recent advances in controlled/living polymerization techniques and highly efficient coupling chemistries have enabled the facile synthesis of complex polymer architectures with controlled dimensions and functionality. As an example, star polymers consist of many linear polymers fused at a central point with a large number of chain end functionalities. Owing to this exclusive structure, star polymers exhibit some remarkable characteristics and properties unattainable by simple linear polymers. Hence, they constitute a unique class of technologically important nanomaterials that have been utilized or are currently under audition for many applications in life sciences and nanotechnologies. This article first provides a comprehensive summary of synthetic strategies towards star polymers, then reviews the latest developments in the synthesis and characterization methods of star macromolecules, and lastly outlines emerging applications and current commercial use of star-shaped polymers. The aim of this work is to promote star polymer research, generate new avenues of scientific investigation, and provide contemporary perspectives on chemical innovation that may expedite the commercialization of new star nanomaterials. We envision in the not-too-distant future star polymers will play an increasingly important role in materials science and nanotechnology in both academic and industrial settings.
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Affiliation(s)
- Jing M Ren
- Polymer Science Group, Department of Chemical and Biomolecular Engineering, The University of Melbourne , Parkville, Victoria 3010, Australia
| | - Thomas G McKenzie
- Polymer Science Group, Department of Chemical and Biomolecular Engineering, The University of Melbourne , Parkville, Victoria 3010, Australia
| | - Qiang Fu
- Polymer Science Group, Department of Chemical and Biomolecular Engineering, The University of Melbourne , Parkville, Victoria 3010, Australia
| | - Edgar H H Wong
- Polymer Science Group, Department of Chemical and Biomolecular Engineering, The University of Melbourne , Parkville, Victoria 3010, Australia
| | - Jiangtao Xu
- Centre for Advanced Macromolecular Design (CAMD) and Australian Centre for NanoMedicine, School of Chemical Engineering, UNSW Australia , Sydney, New South Wales 2052, Australia
| | - Zesheng An
- Institute of Nanochemistry and Nanobiology, College of Environmental and Chemical Engineering, Shanghai University , Shanghai 2000444, People's Republic of China
| | - Sivaprakash Shanmugam
- Centre for Advanced Macromolecular Design (CAMD) and Australian Centre for NanoMedicine, School of Chemical Engineering, UNSW Australia , Sydney, New South Wales 2052, Australia
| | - Thomas P Davis
- ARC Centre of Excellence in Convergent Bio-Nano Science & Technology, Monash Institute of Pharmaceutical Sciences, Monash University , Parkville, Victoria 3052, Australia.,Department of Chemistry, University of Warwick , Coventry CV4 7AL, United Kingdom
| | - Cyrille Boyer
- Centre for Advanced Macromolecular Design (CAMD) and Australian Centre for NanoMedicine, School of Chemical Engineering, UNSW Australia , Sydney, New South Wales 2052, Australia
| | - Greg G Qiao
- Polymer Science Group, Department of Chemical and Biomolecular Engineering, The University of Melbourne , Parkville, Victoria 3010, Australia
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Kubotera A, Saito R. Synthesis of well-defined 3-arm and 6-arm poly(acrylic acid)s via ATRP of methyl acrylate and hydrolyses of 3-arm and 6-arm poly(methyl acrylate)s. Polym J 2016. [DOI: 10.1038/pj.2015.133] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Mohanty AD, Bae C. Transition Metal-Catalyzed Functionalization of Polyolefins Containing CC, CC, and CH Bonds. ADVANCES IN ORGANOMETALLIC CHEMISTRY 2015. [DOI: 10.1016/bs.adomc.2015.08.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Mardyukov A, Studer A. Preparation of Photoactive Polymers and Postmodification via Nitroxide Trapping Under UV Irradiation. Macromol Rapid Commun 2012; 34:94-101. [DOI: 10.1002/marc.201200595] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2012] [Revised: 10/06/2012] [Indexed: 01/31/2023]
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Tebben L, Studer A. Nitroxides: applications in synthesis and in polymer chemistry. Angew Chem Int Ed Engl 2011; 50:5034-68. [PMID: 21538729 DOI: 10.1002/anie.201002547] [Citation(s) in RCA: 505] [Impact Index Per Article: 38.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Indexed: 01/23/2023]
Abstract
This Review describes the application of nitroxides to synthesis and polymer chemistry. The synthesis and physical properties of nitroxides are discussed first. The largest section focuses on their application as stoichiometric and catalytic oxidants in organic synthesis. The oxidation of alcohols and carbanions, as well as oxidative C-C bond-forming reactions are presented along with other typical oxidative transformations. A section is also dedicated to the extensive use of nitroxides as trapping reagents for C-centered radicals in radical chemistry. Alkoxyamines derived from nitroxides are shown to be highly useful precursors of C-centered radicals in synthesis and also in polymer chemistry. The last section discusses the basics of nitroxide-mediated radical polymerization (NMP) and also highlights new developments in the synthesis of complex polymer architectures.
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Affiliation(s)
- Ludger Tebben
- Organisch-Chemisches Institut, Westfälische Wilhelms-Universität, Corrensstrasse 40, 48149 Münster, Germany
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