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Denkler LM, Aladahalli Shekar M, Ngan TSJ, Wylie L, Abdullin D, Engeser M, Schnakenburg G, Hett T, Pilz FH, Kirchner B, Schiemann O, Kielb P, Bunescu A. A General Iron-Catalyzed Decarboxylative Oxygenation of Aliphatic Carboxylic Acids. Angew Chem Int Ed Engl 2024; 63:e202403292. [PMID: 38735849 DOI: 10.1002/anie.202403292] [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] [Received: 02/16/2024] [Revised: 05/07/2024] [Accepted: 05/09/2024] [Indexed: 05/14/2024]
Abstract
We report an iron-catalyzed decarboxylative C(sp3)-O bond-forming reaction under mild, base-free conditions with visible light irradiation. The transformation uses readily available and structurally diverse carboxylic acids, iron photocatalyst, and 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) derivatives as oxygenation reagents. The process exhibits a broad scope in acids possessing a wide range of stereoelectronic properties and functional groups. The developed reaction was applied to late-stage oxygenation of a series of bio-active molecules. The reaction leverages the ability of iron complexes to generate carbon-centered radicals directly from carboxylic acids by photoinduced carboxylate-to-iron charge transfer. Kinetic, electrochemical, EPR, UV/Vis, HRMS, and DFT studies revealed that TEMPO has a triple role in the reaction: as an oxygenation reagent, an oxidant to turn over the Fe-catalyst, and an internal base for the carboxylic acid deprotonation. The obtained TEMPO adducts represent versatile synthetic intermediates that were further engaged in C-C and C-heteroatom bond-forming reactions using commercial organo-photocatalysts and nucleophilic reagents.
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Affiliation(s)
- Luca Mareen Denkler
- Kekulé Institute for Organic Chemistry and Biochemistry, Universität Bonn, Gerhard-Domagk-Straße1, 53121, Bonn, Germany
| | - Meghana Aladahalli Shekar
- Kekulé Institute for Organic Chemistry and Biochemistry, Universität Bonn, Gerhard-Domagk-Straße1, 53121, Bonn, Germany
| | - Tak Shing Jason Ngan
- Kekulé Institute for Organic Chemistry and Biochemistry, Universität Bonn, Gerhard-Domagk-Straße1, 53121, Bonn, Germany
| | - Luke Wylie
- Mulliken Center for Theoretical Chemistry Clausius Institute for Physical and Theoretical Chemistry, Universität Bonn, Beringstraße 4, 53115, Bonn, Germany
| | - Dinar Abdullin
- Clausius Institute for Physical and Theoretical Chemistry, Universität Bonn, Wegelerstraße 12, 53115, Bonn, Germany
- Transdisciplinary Research Area' Building Blocks of Matter and Fundamental Interactions (TRA Matter), University of Bonn, 53115, Bonn, Germany
| | - Marianne Engeser
- Kekulé Institute for Organic Chemistry and Biochemistry, Universität Bonn, Gerhard-Domagk-Straße1, 53121, Bonn, Germany
- Transdisciplinary Research Area' Building Blocks of Matter and Fundamental Interactions (TRA Matter), University of Bonn, 53115, Bonn, Germany
| | - Gregor Schnakenburg
- Institute of Inorganic Chemistry, Universität Bonn, Gerhard-Domagk-Straße1, 53121, Bonn, Germany
| | - Tobias Hett
- Clausius Institute for Physical and Theoretical Chemistry, Universität Bonn, Wegelerstraße 12, 53115, Bonn, Germany
| | - Frank Hendrik Pilz
- Clausius Institute for Physical and Theoretical Chemistry, Universität Bonn, Wegelerstraße 12, 53115, Bonn, Germany
- Transdisciplinary Research Area' Building Blocks of Matter and Fundamental Interactions (TRA Matter), University of Bonn, 53115, Bonn, Germany
| | - Barbara Kirchner
- Mulliken Center for Theoretical Chemistry Clausius Institute for Physical and Theoretical Chemistry, Universität Bonn, Beringstraße 4, 53115, Bonn, Germany
| | - Olav Schiemann
- Clausius Institute for Physical and Theoretical Chemistry, Universität Bonn, Wegelerstraße 12, 53115, Bonn, Germany
- Transdisciplinary Research Area' Building Blocks of Matter and Fundamental Interactions (TRA Matter), University of Bonn, 53115, Bonn, Germany
| | - Patrycja Kielb
- Clausius Institute for Physical and Theoretical Chemistry, Universität Bonn, Wegelerstraße 12, 53115, Bonn, Germany
- Transdisciplinary Research Area' Building Blocks of Matter and Fundamental Interactions (TRA Matter), University of Bonn, 53115, Bonn, Germany
| | - Ala Bunescu
- Kekulé Institute for Organic Chemistry and Biochemistry, Universität Bonn, Gerhard-Domagk-Straße1, 53121, Bonn, Germany
- Transdisciplinary Research Area' Building Blocks of Matter and Fundamental Interactions (TRA Matter), University of Bonn, 53115, Bonn, Germany
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Innocent M, Tanguy C, Gavelle S, Aubineau T, Guérinot A. Iron-Catalyzed, Light-Driven Decarboxylative Alkoxyamination. Chemistry 2024; 30:e202401252. [PMID: 38736425 DOI: 10.1002/chem.202401252] [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: 03/28/2024] [Revised: 05/07/2024] [Accepted: 05/12/2024] [Indexed: 05/14/2024]
Abstract
An iron-catalyzed visible-light driven decarboxylative alkoxyamination is disclosed. In the presence of FeBr2 and TEMPO, a large array of carboxylic acids including marketed drugs and biobased molecules is turned into the corresponding alkoxyamine derivatives. The versatility of the latter offers an entry towards molecular diversity generation from abundant starting materials and catalyst. Overall, this method proposes a unified and general approach for LMCT-based iron-catalyzed decarboxylative functionalization.
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Affiliation(s)
- Milan Innocent
- Molecular, Macromolecular Chemistry and Materials, ESPCI Paris - PSL, CNRS, 10 rue Vauquelin, 75005, Paris, France
| | - Clément Tanguy
- Molecular, Macromolecular Chemistry and Materials, ESPCI Paris - PSL, CNRS, 10 rue Vauquelin, 75005, Paris, France
| | - Sigrid Gavelle
- Molecular, Macromolecular Chemistry and Materials, ESPCI Paris - PSL, CNRS, 10 rue Vauquelin, 75005, Paris, France
| | - Thomas Aubineau
- Molecular, Macromolecular Chemistry and Materials, ESPCI Paris - PSL, CNRS, 10 rue Vauquelin, 75005, Paris, France
| | - Amandine Guérinot
- Molecular, Macromolecular Chemistry and Materials, ESPCI Paris - PSL, CNRS, 10 rue Vauquelin, 75005, Paris, France
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Ortalli S, Ford J, Trabanco AA, Tredwell M, Gouverneur V. Photoredox Nucleophilic (Radio)fluorination of Alkoxyamines. J Am Chem Soc 2024; 146:11599-11604. [PMID: 38651661 PMCID: PMC11066844 DOI: 10.1021/jacs.4c02474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2024] [Revised: 04/19/2024] [Accepted: 04/19/2024] [Indexed: 04/25/2024]
Abstract
Herein, we report a photoredox nucleophilic (radio)fluorination using TEMPO-derived alkoxyamines, a class of substrates accessible in a single step from a diversity of readily available carboxylic acids, halides, alkenes, alcohols, aldehydes, boron reagents, and C-H bonds. This mild and versatile one-electron pathway affords radiolabeled aliphatic fluorides that are typically inaccessible applying conventional nucleophilic substitution technologies due to insufficient reactivity and competitive elimination. Automation of this photoredox process is also demonstrated with a user-friendly and commercially available photoredox flow reactor and radiosynthetic platform, therefore expediting access to labeled aliphatic fluorides in high molar activity (Am) for (pre)clinical evaluation.
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Affiliation(s)
- Sebastiano Ortalli
- Department
of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - Joseph Ford
- Department
of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, United Kingdom
| | - Andrés A. Trabanco
- Global
Discovery Chemistry, Therapeutics Discovery, Johnson & Johnson Innovative Medicine, Janssen-Cilag, S.A., E-45007 Toledo, Spain
| | - Matthew Tredwell
- Wales Research
and Diagnostic PET Imaging Centre, Cardiff
University, University
Hospital of Wales, Heath Park, Cardiff CF14 4XN, United
Kingdom
- School
of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, United Kingdom
| | - Véronique Gouverneur
- Department
of Chemistry, Chemistry Research Laboratory, University of Oxford, Mansfield Road, Oxford OX1 3TA, United Kingdom
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Saito Y, Kobayashi S. Continuous-Flow Enantioselective Hydroacylations under Heterogeneous Chiral Rhodium Catalysts. Angew Chem Int Ed Engl 2024; 63:e202313778. [PMID: 37991463 DOI: 10.1002/anie.202313778] [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: 09/15/2023] [Indexed: 11/23/2023]
Abstract
Transition metal-catalyzed enantioselective C-H bond functionalizations have become efficient methods for the synthesis of complex optically active molecules. Heterogeneous catalysts for this chemistry remain largely unexplored despite the advantages they offer in terms of ease of separation and reuse of catalysts. Herein, we report the development of heterogeneous chiral Rh catalysts for continuous-flow enantioselective hydroacylations. Heterogeneous catalysts could be prepared simply by mixing supports and Rh complexes. The prepared catalysts exhibited excellent activity and enantioselectivity affording optically active ketones in quantitative yields with 99 % ee's. Under the optimized reaction conditions, a turnover number >300 was achieved without the leaching of Rh species. The catalysts exhibited a wide substrate scope and in sequential-flow reactions with other heterogeneous catalysts, the syntheses of biologically active molecules and functional materials were demonstrated.
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Affiliation(s)
- Yuki Saito
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
| | - Shū Kobayashi
- Department of Chemistry, School of Science, The University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
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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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Rehpenn A, Walter A, Storch G. Molecular flavin catalysts for C-H functionalisation and derivatisation of dehydroamino acids. Chem Sci 2022; 13:14151-14156. [PMID: 36540823 PMCID: PMC9728571 DOI: 10.1039/d2sc04341f] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Accepted: 11/04/2022] [Indexed: 03/12/2024] Open
Abstract
In nature, the isoalloxazine heterocycle of flavin cofactors undergoes reversible covalent bond formation with a variety of different reaction partners. These intermediates play a crucial role inter alia as the signalling states and in selective catalysis reactions. In the organic laboratory, covalent adducts with a new carbon-carbon bond have been observed with photochemically excited flavins but have, so far, only been regarded as dead-end side products. We have identified a series of molecular flavins that form adducts resulting in a new C-C bond at the C4a-position through allylic C-H activation and dehydroamino acid oxidation. Typically, these reactions are of radical nature and a stepwise pathway is assumed. We could demonstrate that these adducts are no dead-end and that the labile C-C bond can be cleaved by adding the persistent radical TEMPO leading to flavin regeneration and alkoxyamine-functionalised substrates. Our method allows for the catalytic oxidation of dehydroamino acids (16 examples) and we show that the acylimine products serve as versatile starting points for diversification. The present results are envisioned to stimulate the design of further catalytic reactions involving intermediates at the flavin C4a-position and their reactivity towards metal complexes or other persistent organic radicals. Our method for dehydrobutyrine derivatisation is orthogonal to the currently used methods (i.e., nucleophilic attack or radical addition) and offers new perspectives for peptide natural product diversification.
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Affiliation(s)
- Andreas Rehpenn
- School of Natural Sciences and Catalysis Research Center (CRC), Technical University of Munich (TUM) Lichtenbergstr. 4 85747 Garching Germany
| | - Alexandra Walter
- School of Natural Sciences and Catalysis Research Center (CRC), Technical University of Munich (TUM) Lichtenbergstr. 4 85747 Garching Germany
| | - Golo Storch
- School of Natural Sciences and Catalysis Research Center (CRC), Technical University of Munich (TUM) Lichtenbergstr. 4 85747 Garching Germany
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