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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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Qian B, Zhang L, Zhang G, Fu Y, Zhu X, Shen G. Thermodynamic Evaluation on Alkoxyamines of TEMPO Derivatives, Stable Alkoxyamines or Potential Radical Donors? ChemistrySelect 2022. [DOI: 10.1002/slct.202204144] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Affiliation(s)
- Bao‐Chen Qian
- School of Medical Engineering Jining Medical University Jining Shandong 272000 P. R. China
| | - Lu Zhang
- School of Medical Engineering Jining Medical University Jining Shandong 272000 P. R. China
| | - Gao‐Shuai Zhang
- School of Medical Engineering Jining Medical University Jining Shandong 272000 P. R. China
| | - Yan‐Hua Fu
- College of Chemistry and Environmental Engineering Anyang Institute of Technology Anyang Henan 455000 P. R. China
| | - Xiao‐Qing Zhu
- The State Key Laboratory of Elemento-Organic Chemistry Department of Chemistry Nankai University Tianjin 300071 P. R. China
| | - Guang‐Bin Shen
- School of Medical Engineering Jining Medical University Jining Shandong 272000 P. R. China
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3
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Pérez-Palau M, Balaguer-Garcia E, Romea P, Urpí F. Optimized Asymmetric Synthesis of Umuravumbolide. ACS OMEGA 2022; 7:30835-30840. [PMID: 36092614 PMCID: PMC9453790 DOI: 10.1021/acsomega.2c02304] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/13/2022] [Accepted: 08/04/2022] [Indexed: 06/15/2023]
Abstract
Herein, the asymmetric synthesis of umuravumbolide (1) is described. The new approach features highly stereoselective transformations (dr ≥ 95:5) to install both stereocenters and the Z olefin, which involve a new radical alkylation, an Ando olefination, and a Krische allylation on a Z allylic alcohol, not reported before. The application of such successful reactions, together with the limited use of protecting groups and concession steps, makes it possible to complete the synthesis in 10 steps, resulting in a 39% overall yield from chiral N-acyl oxazolidinone 2.
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Tanaka T, Kiuchi T, Ooe Y, Iwamoto H, Takizawa SY, Murata S, Hasegawa E. A Photocatalytic System Composed of Benzimidazolium Aryloxide and Tetramethylpiperidine 1-Oxyl to Promote Desulfonylative α-Oxyamination Reactions of α-Sulfonylketones. ACS OMEGA 2022; 7:4655-4666. [PMID: 35155957 PMCID: PMC8829864 DOI: 10.1021/acsomega.1c06857] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Accepted: 01/14/2022] [Indexed: 05/19/2023]
Abstract
A new photocatalytic system was developed for carrying out desulfonylative α-oxyamination reactions of α-sulfonylketones in which α-ketoalkyl radicals are generated. The catalytic system is composed of benzimidazolium aryloxide betaines (BI+-ArO-), serving as visible light-absorbing electron donor photocatalysts, and 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO), playing dual roles as an electron donor for catalyst recycling and a reagent to capture the generated radical intermediates. Information about the detailed nature of BI+-ArO- and the photocatalytic processes with TEMPO was gained using absorption spectroscopy, electrochemical measurements, and density functional theory calculations.
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Affiliation(s)
- Tsukasa Tanaka
- Department
of Chemistry, Faculty of Science, Niigata
University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Takehiro Kiuchi
- Department
of Chemistry, Faculty of Science, Niigata
University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Yuuki Ooe
- Department
of Chemistry, Faculty of Science, Niigata
University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Hajime Iwamoto
- Department
of Chemistry, Faculty of Science, Niigata
University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
| | - Shin-ya Takizawa
- Department
of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
| | - Shigeru Murata
- Department
of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, 3-8-1 Komaba, Meguro-ku, Tokyo 153-8902, Japan
| | - Eietsu Hasegawa
- Department
of Chemistry, Faculty of Science, Niigata
University, 8050 Ikarashi-2, Nishi-ku, Niigata 950-2181, Japan
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5
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Pérez-Palau M, Sanosa N, Romea P, Urpí F, López R, Gómez-Bengoa E, Font-Bardia M. Stereoselective Alkylation of Chiral Titanium(IV) Enolates with tert-Butyl Peresters. Org Lett 2021; 23:8852-8856. [PMID: 34699246 PMCID: PMC8609576 DOI: 10.1021/acs.orglett.1c03366] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
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Here, we present
a new stereoselective alkylation of titanium(IV)
enolates of chiral N-acyl oxazolidinones with tert-butyl peresters from Cα-branched aliphatic carboxylic
acids, which proceeds through the decarboxylation of the peresters
and the subsequent formation of alkyl radicals to produce the alkylated
adducts with an excellent diastereoselectivity. Theoretical calculations
account for the observed reactivity and the outstanding stereocontrol.
Importantly, the resultant compounds can be easily converted into
ligands for asymmetric and catalytic transformations.
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Affiliation(s)
- Marina Pérez-Palau
- Secció de Química Orgànica, Departament de Química Inorgànica i Orgànica and Institut de Biomedicina de la Universitat de Barcelona (IBUB), Universitat de Barcelona, Carrer Martí i Franqués 1-11, 08028 Barcelona, Catalonia, Spain
| | - Nil Sanosa
- Secció de Química Orgànica, Departament de Química Inorgànica i Orgànica and Institut de Biomedicina de la Universitat de Barcelona (IBUB), Universitat de Barcelona, Carrer Martí i Franqués 1-11, 08028 Barcelona, Catalonia, Spain
| | - Pedro Romea
- Secció de Química Orgànica, Departament de Química Inorgànica i Orgànica and Institut de Biomedicina de la Universitat de Barcelona (IBUB), Universitat de Barcelona, Carrer Martí i Franqués 1-11, 08028 Barcelona, Catalonia, Spain
| | - Fèlix Urpí
- Secció de Química Orgànica, Departament de Química Inorgànica i Orgànica and Institut de Biomedicina de la Universitat de Barcelona (IBUB), Universitat de Barcelona, Carrer Martí i Franqués 1-11, 08028 Barcelona, Catalonia, Spain
| | - Rosa López
- Departamento de Química Orgánica I, Universidad del Pais Vasco, UPV/EHU, Apdo. 1072, 20080 San Sebastián, Spain
| | - Enrique Gómez-Bengoa
- Departamento de Química Orgánica I, Universidad del Pais Vasco, UPV/EHU, Apdo. 1072, 20080 San Sebastián, Spain
| | - Mercè Font-Bardia
- Unitat de Difracció de RX. CCiTUB. Universitat de Barcelona. Carrer Solé i Sabarís 1-3, 08028 Barcelona, Catalonia, Spain
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6
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Gómez-Palomino A, Pérez-Palau M, Romea P, Urpí F, Del Olmo M, Hesse T, Fleckenstein S, Gómez-Bengoa E, Sotorríos L, Font-Bardia M. Stereoselective Decarboxylative Alkylation of Titanium(IV) Enolates with Diacyl Peroxides. Org Lett 2019; 22:199-203. [PMID: 31825223 DOI: 10.1021/acs.orglett.9b04148] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Simple treatment of chiral titanium(IV) enolates with diacyl peroxides produces highly diastereoselective decarboxylative alkylations to efficiently deliver the corresponding adducts, most of which are not accessible through any of the current alkylating procedures. Such an unprecedented alkylation proceeds through an SET process that triggers the decomposition of the peroxide into a carbon-centered radical that finally combines with the resulting Cα radical. The procedure has been applied to the enantioselective synthesis of arundic acid.
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Affiliation(s)
- Alejandro Gómez-Palomino
- Secció de Química Orgànica, Departament de Química Inorgànica i Orgànica and Institut de Biomedicina de la Universitat de Barcelona (IBUB) , Universitat de Barcelona , Carrer Martí i Franqués 1-11 , 08028 Barcelona , Catalonia , Spain
| | - Marina Pérez-Palau
- Secció de Química Orgànica, Departament de Química Inorgànica i Orgànica and Institut de Biomedicina de la Universitat de Barcelona (IBUB) , Universitat de Barcelona , Carrer Martí i Franqués 1-11 , 08028 Barcelona , Catalonia , Spain
| | - Pedro Romea
- Secció de Química Orgànica, Departament de Química Inorgànica i Orgànica and Institut de Biomedicina de la Universitat de Barcelona (IBUB) , Universitat de Barcelona , Carrer Martí i Franqués 1-11 , 08028 Barcelona , Catalonia , Spain
| | - Fèlix Urpí
- Secció de Química Orgànica, Departament de Química Inorgànica i Orgànica and Institut de Biomedicina de la Universitat de Barcelona (IBUB) , Universitat de Barcelona , Carrer Martí i Franqués 1-11 , 08028 Barcelona , Catalonia , Spain
| | - Marc Del Olmo
- Secció de Química Orgànica, Departament de Química Inorgànica i Orgànica and Institut de Biomedicina de la Universitat de Barcelona (IBUB) , Universitat de Barcelona , Carrer Martí i Franqués 1-11 , 08028 Barcelona , Catalonia , Spain
| | - Timo Hesse
- Secció de Química Orgànica, Departament de Química Inorgànica i Orgànica and Institut de Biomedicina de la Universitat de Barcelona (IBUB) , Universitat de Barcelona , Carrer Martí i Franqués 1-11 , 08028 Barcelona , Catalonia , Spain
| | - Sonja Fleckenstein
- Secció de Química Orgànica, Departament de Química Inorgànica i Orgànica and Institut de Biomedicina de la Universitat de Barcelona (IBUB) , Universitat de Barcelona , Carrer Martí i Franqués 1-11 , 08028 Barcelona , Catalonia , Spain
| | - Enrique Gómez-Bengoa
- Departamento de Química Orgánica I , Universidad del Pais Vasco , UPV/EHU, Apdo. 1072, 20080 San Sebastián , Spain
| | - Lia Sotorríos
- Departamento de Química Orgánica I , Universidad del Pais Vasco , UPV/EHU, Apdo. 1072, 20080 San Sebastián , Spain
| | - Mercè Font-Bardia
- Unitat de Difracció de RX. CCiTUB . Universitat de Barcelona . Carrer Solé i Sabarís 1-3 , 08028 Barcelona , Catalonia , Spain
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7
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Pinto A, Kaiser D, Maryasin B, Di Mauro G, González L, Maulide N. Hydrative Aminoxylation of Ynamides: One Reaction, Two Mechanisms. Chemistry 2018; 24:2515-2519. [PMID: 29293283 PMCID: PMC5838720 DOI: 10.1002/chem.201706063] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2017] [Indexed: 11/08/2022]
Abstract
Organic synthesis boasts a wide array of reactions involving either radical species or ionic intermediates. The combination of radical and polar species, however, has not been explored to a comparable extent. Herein we present the hydrative aminoxylation of ynamides, a reaction which can proceed by either a polar-radical crossover mechanism or through a rare cationic activation. Common to both processes is the versatility of the persistent radical TEMPO and its oxidised oxoammonium derivative TEMPO+ . The unique mechanisms of these processes are elucidated experimentally and by in-depth DFT-calculations.
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Affiliation(s)
- Alexandre Pinto
- Institute of Organic Chemistry, University of Vienna, Währinger Strasse 38, 1090, Vienna, Austria
| | - Daniel Kaiser
- Institute of Organic Chemistry, University of Vienna, Währinger Strasse 38, 1090, Vienna, Austria
| | - Boris Maryasin
- Institute of Organic Chemistry, University of Vienna, Währinger Strasse 38, 1090, Vienna, Austria.,Institute of Theoretical Chemistry, University of Vienna, Währinger Strasse 17, 1090, Vienna, Austria
| | - Giovanni Di Mauro
- Institute of Organic Chemistry, University of Vienna, Währinger Strasse 38, 1090, Vienna, Austria
| | - Leticia González
- Institute of Theoretical Chemistry, University of Vienna, Währinger Strasse 17, 1090, Vienna, Austria
| | - Nuno Maulide
- Institute of Organic Chemistry, University of Vienna, Währinger Strasse 38, 1090, Vienna, Austria
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8
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Kennington SCD, Gómez-Palomino A, Salomó E, Romea P, Urpí F, Font-Bardia M. General and stereoselective aminoxylation of biradical titanium(iv) enolates with TEMPO: a detailed study on the effect of the chiral auxiliary. Org Biomol Chem 2018; 16:4807-4815. [PMID: 29915837 DOI: 10.1039/c8ob01074a] [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
A comprehensive analysis of the influence of the chiral auxiliary on the α-aminoxylation of titanium(iv) enolates with TEMPO indicated that (S) 4-tert-butyl-1-oxazolidine-2-thione is the most appropriate scaffold to provide a single diastereomer in high yields for a variety of substrates, which converts such a radical reaction into a highly chemo- and stereoselective oxidation.
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Affiliation(s)
- Stuart C D Kennington
- Departament de Química Inorgànica i Orgànica, Secció de Química Orgànica, and Institut de Biomedicina (IBUB), Universitat de Barcelona, Carrer Martí i Franqués 1-11, 08028 Barcelona, Catalonia, Spain.
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9
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van Leest NP, Epping RF, van Vliet KM, Lankelma M, van den Heuvel EJ, Heijtbrink N, Broersen R, de Bruin B. Single-Electron Elementary Steps in Homogeneous Organometallic Catalysis. ADVANCES IN ORGANOMETALLIC CHEMISTRY 2018. [DOI: 10.1016/bs.adomc.2018.07.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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