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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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Murray PD, Cox JH, Chiappini ND, Roos CB, McLoughlin EA, Hejna BG, Nguyen ST, Ripberger HH, Ganley JM, Tsui E, Shin NY, Koronkiewicz B, Qiu G, Knowles RR. Photochemical and Electrochemical Applications of Proton-Coupled Electron Transfer in Organic Synthesis. Chem Rev 2022; 122:2017-2291. [PMID: 34813277 PMCID: PMC8796287 DOI: 10.1021/acs.chemrev.1c00374] [Citation(s) in RCA: 163] [Impact Index Per Article: 81.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2021] [Indexed: 12/16/2022]
Abstract
We present here a review of the photochemical and electrochemical applications of multi-site proton-coupled electron transfer (MS-PCET) in organic synthesis. MS-PCETs are redox mechanisms in which both an electron and a proton are exchanged together, often in a concerted elementary step. As such, MS-PCET can function as a non-classical mechanism for homolytic bond activation, providing opportunities to generate synthetically useful free radical intermediates directly from a wide variety of common organic functional groups. We present an introduction to MS-PCET and a practitioner's guide to reaction design, with an emphasis on the unique energetic and selectivity features that are characteristic of this reaction class. We then present chapters on oxidative N-H, O-H, S-H, and C-H bond homolysis methods, for the generation of the corresponding neutral radical species. Then, chapters for reductive PCET activations involving carbonyl, imine, other X═Y π-systems, and heteroarenes, where neutral ketyl, α-amino, and heteroarene-derived radicals can be generated. Finally, we present chapters on the applications of MS-PCET in asymmetric catalysis and in materials and device applications. Within each chapter, we subdivide by the functional group undergoing homolysis, and thereafter by the type of transformation being promoted. Methods published prior to the end of December 2020 are presented.
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Affiliation(s)
- Philip
R. D. Murray
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - James H. Cox
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Nicholas D. Chiappini
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Casey B. Roos
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | | | - Benjamin G. Hejna
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Suong T. Nguyen
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Hunter H. Ripberger
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Jacob M. Ganley
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Elaine Tsui
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Nick Y. Shin
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Brian Koronkiewicz
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Guanqi Qiu
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
| | - Robert R. Knowles
- Department of Chemistry, Princeton
University, Princeton, New Jersey 08544, United States
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3
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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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4
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Photocatalytic
Anti
‐Markovnikov Radical Hydro‐ and Aminooxygenation of Unactivated Alkenes Tuned by Ketoxime Carbonates. Angew Chem Int Ed Engl 2021. [DOI: 10.1002/ange.202107118] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
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5
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Lai SQ, Wei BY, Wang JW, Yu W, Han B. Photocatalytic Anti-Markovnikov Radical Hydro- and Aminooxygenation of Unactivated Alkenes Tuned by Ketoxime Carbonates. Angew Chem Int Ed Engl 2021; 60:21997-22003. [PMID: 34255913 DOI: 10.1002/anie.202107118] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Revised: 06/29/2021] [Indexed: 11/05/2022]
Abstract
A tunable photocatalytic method is reported for anti-Markovnikov hydro- and aminooxygenation of unactivated alkenes using readily accessible ketoxime carbonates as the diverse functionalization reagents. Mechanistic studies reveal that this reaction is initiated through an energy-transfer-promoted N-O bond homolysis of ketoxime carbonates leading to alkoxylcarbonyloxyl and iminyl radicals under visible-light photocatalysis, followed by the addition of alkoxylcarbonyloxyl radical to alkenes. By taking advantage of the different stability of the iminyl radicals, the generated carbon radical either abstracts a hydrogen atom from the media to form the anti-Markovnikov hydrooxygenation product, or it is trapped by the persistent iminyl radical to furnish the aminooxygenation product. Notably, this is the first example of direct hydrooxygenation of unactivated olefins with anti-Markovnikov regioselectivity involving an oxygen-centered radical.
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Affiliation(s)
- Sheng-Qiang Lai
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, P. R. China
| | - Bang-Yi Wei
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, P. R. China
| | - Jia-Wei Wang
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, P. R. China
| | - Wei Yu
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, P. R. China
| | - Bing Han
- State Key Laboratory of Applied Organic Chemistry, College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, 730000, P. R. China
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Krylov IB, Paveliev SA, Budnikov AS, Terent’ev AO. Oxime radicals: generation, properties and application in organic synthesis. Beilstein J Org Chem 2020; 16:1234-1276. [PMID: 32550935 PMCID: PMC7277713 DOI: 10.3762/bjoc.16.107] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2020] [Accepted: 05/15/2020] [Indexed: 12/16/2022] Open
Abstract
N-Oxyl radicals (compounds with an N-O• fragment) represent one of the richest families of stable and persistent organic radicals with applications ranging from catalysis of selective oxidation processes and mechanistic studies to production of polymers, energy storage, magnetic materials design and spectroscopic studies of biological objects. Compared to other N-oxyl radicals, oxime radicals (or iminoxyl radicals) have been underestimated for a long time as useful intermediates for organic synthesis, despite the fact that their precursors, oximes, are extremely widespread and easily available organic compounds. Furthermore, oxime radicals are structurally exceptional. In these radicals, the N-O• fragment is connected to an organic moiety by a double bond, whereas all other classes of N-oxyl radicals contain an R2N-O• fragment with two single C-N bonds. Although oxime radicals have been known since 1964, their broad synthetic potential was not recognized until the last decade, when numerous selective reactions of oxidative cyclization, functionalization, and coupling mediated by iminoxyl radicals were discovered. This review is focused on the synthetic methods based on iminoxyl radicals developed in the last ten years and also contains some selected data on previous works regarding generation, structure, stability, and spectral properties of these N-oxyl radicals. The reactions of oxime radicals are classified into intermolecular (oxidation by oxime radicals, oxidative C-O coupling) and intramolecular. The majority of works are devoted to intramolecular reactions of oxime radicals. These reactions are classified into cyclizations involving C-H bond cleavage and cyclizations involving a double C=C bond cleavage.
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Affiliation(s)
- Igor B Krylov
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, Moscow, 119991, Russia
| | - Stanislav A Paveliev
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, Moscow, 119991, Russia
| | - Alexander S Budnikov
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, Moscow, 119991, Russia
| | - Alexander O Terent’ev
- N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Leninsky Prospect 47, Moscow, 119991, Russia
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7
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Chatgilialoglu C, Ferreri C, Landais Y, Timokhin VI. Thirty Years of (TMS)3SiH: A Milestone in Radical-Based Synthetic Chemistry. Chem Rev 2018; 118:6516-6572. [DOI: 10.1021/acs.chemrev.8b00109] [Citation(s) in RCA: 138] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Affiliation(s)
| | - Carla Ferreri
- ISOF, Consiglio Nazionale delle Ricerche, Via P. Gobetti 101, 40129 Bologna, Italy
| | - Yannick Landais
- University of Bordeaux, Institute of Molecular Sciences, UMR-CNRS 5255, 351 cours de la libération, 33405 Talence Cedex, France
| | - Vitaliy I. Timokhin
- Department of Biochemistry, University of Wisconsin-Madison, 1552 University Avenue, Madison, Wisconsin 53726, United States
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Ramakrishna I, Ramaraju P, Baidya M. Synthesis of Chiral 1,2-Oxazinanes and Isoxazolidines via Nitroso Aldol Reaction of Distal Dialdehydes. Org Lett 2018; 20:1023-1026. [DOI: 10.1021/acs.orglett.7b03968] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Isai Ramakrishna
- Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, India
| | - Panduga Ramaraju
- Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, India
| | - Mahiuddin Baidya
- Department of Chemistry, Indian Institute of Technology Madras, Chennai 600 036, India
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Fekete B, Palkó M, Haukka M, Fülöp F. Synthesis of Pyrrolo[1,2-a]pyrimidine Enantiomers via Domino Ring-Closure followed by Retro Diels-Alder Protocol. Molecules 2017; 22:molecules22040613. [PMID: 28406463 PMCID: PMC6154686 DOI: 10.3390/molecules22040613] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2017] [Revised: 04/04/2017] [Accepted: 04/06/2017] [Indexed: 01/14/2023] Open
Abstract
From 2-aminonorbornene hydroxamic acids, a simple and efficient method for the preparation of pyrrolo[1,2-a]pyrimidine enantiomers is reported. The synthesis is based on domino ring-closure followed by microwave-induced retro Diels-Alder (RDA) protocols, where the chirality of the desired products is transferred from norbornene derivatives. The stereochemistry of the synthesized compounds was proven by X-ray crystallography. The absolute configuration of the product is determined by the configuration of the starting amino hydroxamic acid.
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Affiliation(s)
- Beáta Fekete
- Institute of Pharmaceutical Chemistry, University of Szeged, Eötvös utca 6, Szeged H-6720, Hungary.
| | - Márta Palkó
- Institute of Pharmaceutical Chemistry, University of Szeged, Eötvös utca 6, Szeged H-6720, Hungary.
| | - Matti Haukka
- Department of Chemistry, University of Jyväskylä, FIN-40014 Turku, Finland.
| | - Ferenc Fülöp
- Institute of Pharmaceutical Chemistry, University of Szeged, Eötvös utca 6, Szeged H-6720, Hungary.
- MTA-SZTE Stereochemistry Research Group, Hungarian Academy of Sciences, Eötvös utca 6, Szeged H-6720, Hungary.
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10
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Visible-light- induced aerobic dioxygenation of styrenes under metal- and additive-free ambient conditions. Tetrahedron Lett 2017. [DOI: 10.1016/j.tetlet.2016.12.073] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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11
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Krylov IB, Paveliev SA, Shelimov BN, Lokshin BV, Garbuzova IA, Tafeenko VA, Chernyshev VV, Budnikov AS, Nikishin GI, Terent'ev AO. Selective cross-dehydrogenative C–O coupling of N-hydroxy compounds with pyrazolones. Introduction of the diacetyliminoxyl radical into the practice of organic synthesis. Org Chem Front 2017. [DOI: 10.1039/c7qo00447h] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Oxidative C–O coupling of oximes, N-hydroxyphthalimide, and N-hydroxybenzotriazole with pyrazolones via formation of N-oxyl radicals is described.
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Affiliation(s)
- Igor B. Krylov
- N. D. Zelinsky Institute of Organic Chemistry of the Russian Academy of Sciences
- Moscow 119991
- Russian Federation
| | - Stanislav A. Paveliev
- N. D. Zelinsky Institute of Organic Chemistry of the Russian Academy of Sciences
- Moscow 119991
- Russian Federation
| | - Boris N. Shelimov
- N. D. Zelinsky Institute of Organic Chemistry of the Russian Academy of Sciences
- Moscow 119991
- Russian Federation
| | - Boris V. Lokshin
- A. N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences
- Moscow 119991
- Russian Federation
| | - Irina A. Garbuzova
- A. N. Nesmeyanov Institute of Organoelement Compounds of the Russian Academy of Sciences
- Moscow 119991
- Russian Federation
| | - Viktor A. Tafeenko
- Department of Chemistry
- M.V. Lomonosov Moscow State University
- Moscow 119991
- Russian Federation
| | - Vladimir V. Chernyshev
- Department of Chemistry
- M.V. Lomonosov Moscow State University
- Moscow 119991
- Russian Federation
- A. N. Frumkin Institute of Physical Chemistry and Electrochemistry RAS
| | - Alexander S. Budnikov
- N. D. Zelinsky Institute of Organic Chemistry of the Russian Academy of Sciences
- Moscow 119991
- Russian Federation
- Higher Chemical College of the Russian Academy of Sciences
- Mendeleev University of Chemical Technology of Russia
| | - Gennady I. Nikishin
- N. D. Zelinsky Institute of Organic Chemistry of the Russian Academy of Sciences
- Moscow 119991
- Russian Federation
| | - Alexander O. Terent'ev
- N. D. Zelinsky Institute of Organic Chemistry of the Russian Academy of Sciences
- Moscow 119991
- Russian Federation
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12
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Modem S, Kankala S, Balaboina R, Thirukovela NS, Jonnalagadda SB, Vadde R, Vasam CS. Decarbonylation of Salicylaldehyde Activated byp-Cymene Ruthenium(II) Dimer: Implication for Catalytic Alkyne Hydrothiolation. European J Org Chem 2016. [DOI: 10.1002/ejoc.201600809] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Affiliation(s)
- Sarangapani Modem
- Department of Chemistry; Kakatiya University; 506009 Warangal Telangana State India
| | - Shravankumar Kankala
- Department of Chemistry; Kakatiya University; 506009 Warangal Telangana State India
- School of Chemistry and Physics; University of Kwazulu-Natal; Westville Compus, Chiltern Hills 4000 Durban South Africa
| | - Ramesh Balaboina
- Department of Chemistry; Kakatiya University; 506009 Warangal Telangana State India
| | | | - Sreekantha B. Jonnalagadda
- School of Chemistry and Physics; University of Kwazulu-Natal; Westville Compus, Chiltern Hills 4000 Durban South Africa
| | - Ravinder Vadde
- Department of Chemistry; Kakatiya University; 506009 Warangal Telangana State India
| | - Chandra Sekhar Vasam
- Department of Chemistry; Satavahana University; Karimnagar Telangana State India
- Department of Pharmaceutical Chemistry; Telangana University; Nizamabad Telangana State India
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13
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Fekete B, Palkó M, Mándity I, Haukka M, Fülöp F. A Domino Ring-Closure Followed by Retro-Diels-Alder Reaction for the Preparation of Pyrimido[2,1-a]isoindole Enantiomers. European J Org Chem 2016. [DOI: 10.1002/ejoc.201600434] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Beáta Fekete
- Institute of Pharmaceutical Chemistry; University of Szeged; Eötvös utca 6 6720 Szeged Hungary
| | - Márta Palkó
- Institute of Pharmaceutical Chemistry; University of Szeged; Eötvös utca 6 6720 Szeged Hungary
| | - István Mándity
- Institute of Pharmaceutical Chemistry; University of Szeged; Eötvös utca 6 6720 Szeged Hungary
| | - Matti Haukka
- Department of Chemistry; University of Jyväskylä; 40014 Turku Finland
| | - Ferenc Fülöp
- Institute of Pharmaceutical Chemistry; University of Szeged; Eötvös utca 6 6720 Szeged Hungary
- MTA-SZTE Stereochemistry Research Group; Hungarian Academy of Sciences; Eötvös utca 6 6720 Szeged Hungary
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Bag R, Sar D, Punniyamurthy T. Iron(iii)-catalyzed aerobic dioxygenation of styrenes using N-hydroxyphthalimide and N-hydroxybenzotriazole. Org Biomol Chem 2016; 14:3246-55. [DOI: 10.1039/c6ob00210b] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The dioxygenation of alkenes with NHPI/HOBt in air is described using commercial iron salt as the catalyst under ambient conditions with a broad substrate scope and functional group tolerance. The products can be readily converted into the corresponding 1,2-diols in high yields.
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Affiliation(s)
- Raghunath Bag
- Department of Chemistry
- Indian Institute of Technology Guwahati
- Guwahati 781039
- India
| | - Dinabandhu Sar
- Department of Chemistry
- Indian Institute of Technology Guwahati
- Guwahati 781039
- India
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Lu Q, Peng P, Luo Y, Zhao Y, Zhou M, Lei A. Copper-Catalyzed Aerobic Decarboxylation/Ketooxygenation of Electron-Deficient Alkenes. Chemistry 2015; 21:18580-3. [DOI: 10.1002/chem.201503716] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2015] [Indexed: 12/12/2022]
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