1
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Abdellaoui M, Oppel K, Vianna A, Soleilhavoup M, Yan X, Melaimi M, Bertrand G. 1 H-1,2,3-Triazol-5-ylidenes as Catalytic Organic Single-Electron Reductants. J Am Chem Soc 2024; 146:2933-2938. [PMID: 38253007 DOI: 10.1021/jacs.3c14360] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Most of the known single-electron reductants are either metal based reagents, used in a stoichiometric amount, or a combination of an organic species and a photocatalyst. Here we report that 1H-1,2,3-triazol-5-ylidenes act not only as stoichiometric one-electron donors but also as catalytic organic reducing agents, without the need of a photocatalyst. As a proof of concept, we studied the reduction of quinones, which are well-known electron conveyors that are involved in various biological and industrial processes. This work also provides experimental evidence for the formation of a bis(triazolium)carbonate adduct, which acts as the resting state of the catalytic cycle and as the carbene reservoir.
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Affiliation(s)
- Mehdi Abdellaoui
- UCSD-CNRS Joint Research Laboratory (IRL3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, United States
| | - Kai Oppel
- UCSD-CNRS Joint Research Laboratory (IRL3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, United States
| | - Adam Vianna
- UCSD-CNRS Joint Research Laboratory (IRL3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, United States
| | - Michele Soleilhavoup
- UCSD-CNRS Joint Research Laboratory (IRL3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, United States
| | - Xiaoyu Yan
- Key Laboratory of Advanced Light Conversion Materials and Biophotonics, Department of Chemistry, Renmin University of China, Beijing,100872, China
| | - Mohand Melaimi
- UCSD-CNRS Joint Research Laboratory (IRL3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, United States
| | - Guy Bertrand
- UCSD-CNRS Joint Research Laboratory (IRL3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, California 92093-0358, United States
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2
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Helling C, van der Zee LJC, Hofman J, de Zwart FJ, Mathew S, Nieger M, Slootweg JC. Homolytic C-H Bond Activation by Phosphine-Quinone-Based Radical Ion Pairs. Angew Chem Int Ed Engl 2023; 62:e202313397. [PMID: 37831966 DOI: 10.1002/anie.202313397] [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: 09/09/2023] [Revised: 10/04/2023] [Accepted: 10/13/2023] [Indexed: 10/15/2023]
Abstract
Herein, we present the formation of transient radical ion pairs (RIPs) by single-electron transfer (SET) in phosphine-quinone systems and explore their potential for the activation of C-H bonds. PMes3 (Mes=2,4,6-Me3 C6 H2 ) reacts with DDQ (2,3-dichloro-5,6-dicyano-1,4-benzoquinone) with formation of the P-O bonded zwitterionic adduct Mes3 P-DDQ (1), while the reaction with the sterically more crowded PTip3 (Tip=2,4,6-iPr3 C6 H2 ) afforded C-H bond activation product Tip2 P(H)(2-[CMe2 (DDQ)]-4,6-iPr2 -C6 H2 ) (2). UV/Vis and EPR spectroscopic studies showed that the latter reaction proceeds via initial SET, forming RIP [PTip3 ]⋅+ [DDQ]⋅- , and subsequent homolytic C-H bond activation, which was supported by DFT calculations. The isolation of analogous products, Tip2 P(H)(2-[CMe2 {TCQ-B(C6 F5 )3 }]-4,6-iPr2 -C6 H2 ) (4, TCQ=tetrachloro-1,4-benzoquinone) and Tip2 P(H)(2-[CMe2 {oQtBu -B(C6 F5 )3 }]-4,6-iPr2 -C6 H2 ) (8, oQtBu =3,5-di-tert-butyl-1,2-benzoquinone), from reactions of PTip3 with Lewis-acid activated quinones, TCQ-B(C6 F5 )3 and oQtBu -B(C6 F5 )3 , respectively, further supports the proposed radical mechanism. As such, this study presents key mechanistic insights into the homolytic C-H bond activation by the synergistic action of radical ion pairs.
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Affiliation(s)
- Christoph Helling
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090, GD Amsterdam, The Netherlands
| | - Lars J C van der Zee
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090, GD Amsterdam, The Netherlands
| | - Jelle Hofman
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090, GD Amsterdam, The Netherlands
| | - Felix J de Zwart
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090, GD Amsterdam, The Netherlands
| | - Simon Mathew
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090, GD Amsterdam, The Netherlands
| | - Martin Nieger
- Department of Chemistry, University of Helsinki, A. I. Virtasen aukio 1, P.O. Box 55, FIN-00014, Helsinki, Finland
| | - J Chris Slootweg
- Van't Hoff Institute for Molecular Sciences, University of Amsterdam, PO Box 94157, 1090, GD Amsterdam, The Netherlands
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3
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Loh YK, Melaimi M, Gembicky M, Munz D, Bertrand G. A crystalline doubly oxidized carbene. Nature 2023; 623:66-70. [PMID: 37730995 DOI: 10.1038/s41586-023-06539-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Accepted: 08/14/2023] [Indexed: 09/22/2023]
Abstract
The chemistry of carbon is governed by the octet rule, which refers to its tendency to have eight electrons in its valence shell. However, a few exceptions do exist, for example, the trityl radical (Ph3C∙) (ref. 1) and carbocation (Ph3C+) (ref. 2) with seven and six valence electrons, respectively, and carbenes (R2C:)-two-coordinate octet-defying species with formally six valence electrons3. Carbenes are now powerful tools in chemistry, and have even found applications in material and medicinal sciences4. Can we undress the carbene further by removing its non-bonding electrons? Here we describe the synthesis of a crystalline doubly oxidized carbene (R2C2+), through a two-electron oxidation/oxide-ion abstraction sequence from an electron-rich carbene5. Despite a cumulenic structure and strong delocalization of the positive charges, the dicoordinate carbon centre maintains significant electrophilicity, and possesses two accessible vacant orbitals. A two-electron reduction/deprotonation sequence regenerates the parent carbene, fully consistent with its description as a doubly oxidized carbene. This work demonstrates that the use of bulky strong electron-donor substituents can simultaneously impart electronic stabilization and steric protection to both vacant orbitals on the central carbon atom, paving the way for the isolation of a variety of doubly oxidized carbenes.
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Affiliation(s)
- Ying Kai Loh
- UCSD-CNRS Joint Research Laboratory (IRL 3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, USA.
| | - Mohand Melaimi
- UCSD-CNRS Joint Research Laboratory (IRL 3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, USA
| | - Milan Gembicky
- UCSD-CNRS Joint Research Laboratory (IRL 3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, USA
| | - Dominik Munz
- Coordination Chemistry, Saarland University, Saarbrücken, Germany
| | - Guy Bertrand
- UCSD-CNRS Joint Research Laboratory (IRL 3555), Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, USA.
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4
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Herbstritt D, Tomar P, Braun T. Activation of SF 5CF 3 by the N-Heterocyclic Carbene SIMes. Molecules 2023; 28:6693. [PMID: 37764468 PMCID: PMC10535660 DOI: 10.3390/molecules28186693] [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: 08/24/2023] [Revised: 09/06/2023] [Accepted: 09/14/2023] [Indexed: 09/29/2023] Open
Abstract
The greenhouse gas SF5CF3 was photochemically activated with SIMes (1,3-Bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene) to give 1,3-dimesityl-2,2-difluoroimidazolidine (SIMesF2), and 1,3-dimesitylimidazolidine-2-sulfide, as well as the trifluoromethylated carbene derivative 1,3-dimesityl-2-fluoro-2-trifluoromethylimidazolidine. CF3 radicals, as well as SF4, serve presumably as intermediates of the conversions. In addition, the photochemical activation of SF5CF3 was performed in the presence of triphenylphosphine. The formation of triphenyldifluorophosphorane and triphenylphosphine sulfide was observed.
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Affiliation(s)
| | | | - Thomas Braun
- Department of Chemistry, Humboldt–Universität zu Berlin, Brook-Taylor-Str. 2, 12489 Berlin, Germany
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5
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Ju M, Lu Z, Novaes LFT, Alvarado JIM, Lin S. Frustrated Radical Pairs in Organic Synthesis. J Am Chem Soc 2023; 145:19478-19489. [PMID: 37656899 PMCID: PMC10625356 DOI: 10.1021/jacs.3c07070] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/03/2023]
Abstract
Frustrated radical pairs (FRPs) describe the phenomenon that two distinct radicals─which would otherwise annihilate each other to form a closed-shell covalent adduct─can coexist in solution, owing to steric repulsion or weak bonding association. FRPs are typically formed via spontaneous single-electron transfer between two sterically encumbered precursors─an oxidant and a reductant─under ambient conditions. The two components of a FRP exhibit orthogonal chemical properties and can often act in cooperativity to achieve interesting radical reactivities. Initially observed in the study of traditional frustrated Lewis pairs, FRPs have recently been shown to be capable of homolytically activating various chemical bonds. In this Perspective, we will discuss the discovery of FRPs, their fundamental reactivity in chemical bond activation, and recent developments of their use in synthetic organic chemistry, including in C-H bond functionalization. We anticipate that FRPs will provide new reaction strategies for solving challenging problems in modern organic synthesis.
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Affiliation(s)
| | | | - Luiz F. T. Novaes
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | | | - Song Lin
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
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6
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van der Zee LJ, Pahar S, Richards E, Melen RL, Slootweg JC. Insights into Single-Electron-Transfer Processes in Frustrated Lewis Pair Chemistry and Related Donor-Acceptor Systems in Main Group Chemistry. Chem Rev 2023; 123:9653-9675. [PMID: 37431868 PMCID: PMC10416219 DOI: 10.1021/acs.chemrev.3c00217] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2023] [Indexed: 07/12/2023]
Abstract
The activation and utilization of substrates mediated by Frustrated Lewis Pairs (FLPs) was initially believed to occur solely via a two-electron, cooperative mechanism. More recently, the occurrence of a single-electron transfer (SET) from the Lewis base to the Lewis acid was observed, indicating that mechanisms that proceed via one-electron-transfer processes are also feasible. As such, SET in FLP systems leads to the formation of radical ion pairs, which have recently been more frequently observed. In this review, we aim to discuss the seminal findings regarding the recently established insights into the SET processes in FLP chemistry as well as highlight examples of this radical formation process. In addition, applications of reported main group radicals will also be reviewed and discussed in the context of the understanding of SET processes in FLP systems.
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Affiliation(s)
- Lars J.
C. van der Zee
- Van
’t Hoff Institute for Molecular Sciences, University of Amsterdam, P.O. Box 94157, 1090 GD Amsterdam, The Netherlands
| | - Sanjukta Pahar
- Cardiff
Catalysis Institute, Cardiff University, Translational Research Hub, Maindy
Road, Cathays, Cardiff, CF24 4HQ Wales, United Kingdom
| | - Emma Richards
- Cardiff
Catalysis Institute, Cardiff University, Translational Research Hub, Maindy
Road, Cathays, Cardiff, CF24 4HQ Wales, United Kingdom
| | - Rebecca L. Melen
- Cardiff
Catalysis Institute, Cardiff University, Translational Research Hub, Maindy
Road, Cathays, Cardiff, CF24 4HQ Wales, United Kingdom
| | - J. Chris Slootweg
- Van
’t Hoff Institute for Molecular Sciences, University of Amsterdam, P.O. Box 94157, 1090 GD Amsterdam, The Netherlands
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7
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Delfau L, Assani N, Nichilo S, Pecaut J, Philouze C, Broggi J, Martin D, Tomás-Mendivil E. On the Redox Properties of the Dimers of Thiazol-2-ylidenes That Are Relevant for Radical Catalysis. ACS ORGANIC & INORGANIC AU 2023; 3:136-142. [PMID: 37303499 PMCID: PMC10251502 DOI: 10.1021/acsorginorgau.3c00008] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 03/23/2023] [Accepted: 03/23/2023] [Indexed: 06/13/2023]
Abstract
We report the isolation and study of dimers stemming from popular thiazol-2-ylidene organocatalysts. The model featuring 2,6-di(isopropyl)phenyl (Dipp) N-substituents was found to be a stronger reducing agent (Eox = -0.8 V vs SCE) than bis(thiazol-2-ylidenes) previously studied in the literature. In addition, a remarkable potential gap between the first and second oxidation of the dimer also allows for the isolation of the corresponding air-persistent radical cation. The latter is an unexpected efficient promoter of the radical transformation of α-bromoamides into oxindoles.
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Affiliation(s)
| | - Nadhrata Assani
- Aix
Marseille Univ., CNRS, Institut de Chimie Radicalaire - UMR 7273,
Faculté de Pharmacie, 13005 Marseille, France
| | | | - Jacques Pecaut
- Univ.
Grenoble Alpes, CEA, CNRS, INAC-SyMMES, UMR 5819 38000 Grenoble, France
| | | | - Julie Broggi
- Aix
Marseille Univ., CNRS, Institut de Chimie Radicalaire - UMR 7273,
Faculté de Pharmacie, 13005 Marseille, France
| | - David Martin
- Univ.
Grenoble Alpes, CNRS, DCM, 38000 Grenoble, France
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8
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Jana S, Elvers BJ, Pätsch S, Sarkar P, Krummenacher I, Nayak MK, Maiti A, Chrysochos N, Pati SK, Schulzke C, Braunschweig H, Yildiz CB, Jana A. Air and Moisture Stable para- and ortho-Quinodimethane Derivatives Derived from bis- N-Heterocyclic Olefins. Org Lett 2023; 25:1799-1804. [PMID: 36662600 DOI: 10.1021/acs.orglett.2c03993] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Herein we report the development of a new methodology for the synthesis of various quinodimethane derivatives under two-electron oxidation of bis-N-heterocyclic olefins linked by different π-conjugated aromatic spacers. In case of para- and ortho-phenylene bridge, we obtained air and moisture stable diimidazolium para- and ortho-quinodimethane derivatives. Analogues of the para-phenylene spacer such as tetrafluoro-p-phenylene and p-anthracene also led to the corresponding air and moisture stable quinodimethane derivatives. This emphasizes the influence of imidazolium substituents which facilitate the air and moisture stability of the quinodimethane derivatives. Differences were observed for the electron transfer processes: two one-electron vs one two-electron redox transitions between bis-N-heterocyclic olefins and diimidazolium-quinodimethanes depending on the employed π-conjugated aromatic spacer. The formation of the π-conjugated radical-cations, transient redox intermediates between bis-N-heterocyclic olefins and diimidazolium-quinodimethanes, was addressed by an EPR investigation.
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Affiliation(s)
- Subhadip Jana
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, India
| | - Benedict J Elvers
- Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Straße 4, D-17489 Greifswald, Germany
| | - Sebastian Pätsch
- Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Straße 4, D-17489 Greifswald, Germany
| | - Pallavi Sarkar
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064, India
| | - Ivo Krummenacher
- Institute of Inorganic Chemistry and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Mithilesh Kumar Nayak
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, India
| | - Avijit Maiti
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, India
| | - Nicolas Chrysochos
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, India
| | - Swapan K Pati
- Theoretical Sciences Unit, Jawaharlal Nehru Centre for Advanced Scientific Research, Bangalore 560064, India
| | - Carola Schulzke
- Institut für Biochemie, Universität Greifswald, Felix-Hausdorff-Straße 4, D-17489 Greifswald, Germany
| | - Holger Braunschweig
- Institute of Inorganic Chemistry and Institute for Sustainable Chemistry & Catalysis with Boron, Julius-Maximilians-Universität Würzburg, Am Hubland, 97074 Würzburg, Germany
| | - Cem B Yildiz
- Department of Aromatic and Medicinal Plants, University of Aksaray, Aksaray 68100, Turkey
| | - Anukul Jana
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500046, India
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9
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Song H, Lee E. Revisiting the Reaction of IPr with Tritylium: An Alternative Mechanistic Pathway. Chemistry 2023; 29:e202203364. [PMID: 36445754 DOI: 10.1002/chem.202203364] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Revised: 11/29/2022] [Accepted: 11/29/2022] [Indexed: 11/30/2022]
Abstract
Despite a recent proposal on the mechanism of a single-electron transfer (SET) process between tritylium and 2,6-bis(diisopropylphenyl)imidazol-2-ylidene (IPr) based on evidence of transient IPr radical cation intermediate ([IPr]⋅+ ) formation, such oxidation is still contentious because of the high oxidation potential of N-heterocyclic carbenes. Our experimental analysis indicates that the appearance of deep purple color, previously considered to be from transient [IPr]⋅+ , originates from a zwitterionic intermediate (3 a), not a radical cation. Here, we propose an alternative mechanism for the reaction involving tritylium and IPr. This mechanism is noteworthy for explaining how [NHC-H]+ can be generated without the formation of transient [NHC]⋅+ , which has been frequently proposed as an intermediate for the reaction between NHC and oxidants. These results also show that a transient strong single-electron donor (3 a) could be generated by the alternative mechanism for oxidants using NHCs, which is a more feasible explanation for the reactivity of NHCs with oxidants.
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Affiliation(s)
- Hayoung Song
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea
| | - Eunsung Lee
- Department of Chemistry, Pohang University of Science and Technology (POSTECH), Pohang, 37673, Republic of Korea.,Division of Advanced Materials Science, Pohang University of Science and Technology, Pohang, 37673, Republic of Korea
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10
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Li Q, Zhou CY, Wang C. Metal-Free Generation of γ-Cyanoalkyl Radicals by N-Heterocyclic Carbene Catalysis: Assembly of 6-Cyanoalkyl Phenanthridines. Org Lett 2022; 24:9243-9247. [PMID: 36516358 DOI: 10.1021/acs.orglett.2c03808] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
A number of γ-cyanoalkyl radicals were generated by sustainable N-heterocyclic carbene catalysis in tin-, transition-meal-, and light-free conditions, followed by insertion into biaryl isonitriles, thus leading to the rapid assembly of a variety of diversely functionalized 6-cyanoalkyl phenanthridines. A preliminary mechanism study revealed that a single-electron transfer radical process was possibly involved.
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Affiliation(s)
- Qianrong Li
- College of Chemistry and Materials Science, Guangdong Provincial Key Laboratory of Functional Supramolecular Coordination Materials and Applications, Jinan University, Guangzhou, Guangdong511443, People's Republic of China
| | - Cong-Ying Zhou
- College of Chemistry and Materials Science, Guangdong Provincial Key Laboratory of Functional Supramolecular Coordination Materials and Applications, Jinan University, Guangzhou, Guangdong511443, People's Republic of China
| | - Chengming Wang
- College of Chemistry and Materials Science, Guangdong Provincial Key Laboratory of Functional Supramolecular Coordination Materials and Applications, Jinan University, Guangzhou, Guangdong511443, People's Republic of China
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11
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Zhao Z, Tan J, Chen T, Hussain Z, Li Y, Wu Y, Stephan DW. Ambiphilic Behavior of Ge(II)-Pseudohalides in Inter- and Intramolecular Frustrated Lewis Pair Alkyne Addition Reactions. Inorg Chem 2022; 61:18670-18677. [DOI: 10.1021/acs.inorgchem.2c03171] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Zhao Zhao
- Institute of Drug Discovery Technology, Ningbo University, Ningbo 315211 Zhejiang, China
| | - Jingjie Tan
- Institute of Drug Discovery Technology, Ningbo University, Ningbo 315211 Zhejiang, China
| | - Ting Chen
- Institute of Drug Discovery Technology, Ningbo University, Ningbo 315211 Zhejiang, China
| | - Zahid Hussain
- Institute of Drug Discovery Technology, Ningbo University, Ningbo 315211 Zhejiang, China
| | - Yanguo Li
- Institute of Drug Discovery Technology, Ningbo University, Ningbo 315211 Zhejiang, China
| | - Yile Wu
- Institute of Drug Discovery Technology, Ningbo University, Ningbo 315211 Zhejiang, China
- State Key Laboratory of Elemento-Organic Chemistry, Nankai University, Tianjin 300071, China
| | - Douglas W. Stephan
- Department of Chemistry, University of Toronto, 80 St. George Street, Toronto M5S3H6, Ontario, Canada
- Institute of Drug Discovery Technology, Ningbo University, Ningbo 315211 Zhejiang, China
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12
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Liu L, Zhang Q, Wang C. Redox-Neutral Generation of Iminyl Radicals by N-Heterocyclic Carbene Catalysis: Rapid Access to Phenanthridines from Vinyl Azides. Org Lett 2022; 24:5913-5917. [PMID: 35925779 DOI: 10.1021/acs.orglett.2c02118] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An N-heterocyclic carbene-catalyzed oxidant-, metal- and light-free iminyl radical generation pathway stemming from the reaction of vinyl azide and α-bromo ester is uncovered. This newly developed methodology is successfully applied to the redox-neutral construction of a number of diversified phenanthridine derivatives with nice functional group compatibility. Insights from the mechanism study reveal that this NHC-catalyzed transformation potentially proceeds through an alkyl radical addition-initiated HAS process, with the iminyl radical as an active intermediate.
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Affiliation(s)
- Lixia Liu
- College of Chemistry and Materials Science, Guangdong Provincial Key Laboratory of Functional Supramolecular Coordination Materials and Applications, Jinan University, Guangzhou, Guangdong511443, China
| | - Qijing Zhang
- College of Chemistry and Materials Science, Guangdong Provincial Key Laboratory of Functional Supramolecular Coordination Materials and Applications, Jinan University, Guangzhou, Guangdong511443, China
| | - Chengming Wang
- College of Chemistry and Materials Science, Guangdong Provincial Key Laboratory of Functional Supramolecular Coordination Materials and Applications, Jinan University, Guangzhou, Guangdong511443, China
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13
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Hoffmann KF, Battke D, Golz P, Rupf SM, Malischewski M, Riedel S. The Tris(pentafluorophenyl)methylium Cation: Isolation and Reactivity. Angew Chem Int Ed Engl 2022; 61:e202203777. [PMID: 35416383 PMCID: PMC9401592 DOI: 10.1002/anie.202203777] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2022] [Indexed: 11/09/2022]
Abstract
Herein, we present two different routes for the synthesis of the perfluorinated trityl cation, which allowed the handling of the free, uncoordinated species in organic solvents for the first time. The usage of the weakly coordinating anion [Al(OTeF5)4]− and its derivatives allows the characterization of this species by NMR spectroscopy and most importantly by single‐crystal X‐ray diffraction. The high hydride ion affinity of the cation is shown by hydrogen abstraction from isobutane. Furthermore, cyclic voltammetry reveals its oxidative potential which is supported by the reaction with tris(4‐bromophenyl)amine, giving rise to the formation of the ammoniumyl radical cation, also known as “magic blue”.
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Affiliation(s)
- Kurt F. Hoffmann
- Fachbereich für Biologie, Chemie, Pharmazie Institut für Chemie und Biochemie—Anorganische Chemie Fabeckstraße 34/36 14195 Berlin Germany
| | - David Battke
- Fachbereich für Biologie, Chemie, Pharmazie Institut für Chemie und Biochemie—Anorganische Chemie Fabeckstraße 34/36 14195 Berlin Germany
| | - Paul Golz
- Fachbereich für Biologie, Chemie, Pharmazie Institut für Chemie und Biochemie—Anorganische Chemie Fabeckstraße 34/36 14195 Berlin Germany
| | - Susanne M. Rupf
- Fachbereich für Biologie, Chemie, Pharmazie Institut für Chemie und Biochemie—Anorganische Chemie Fabeckstraße 34/36 14195 Berlin Germany
| | - Moritz Malischewski
- Fachbereich für Biologie, Chemie, Pharmazie Institut für Chemie und Biochemie—Anorganische Chemie Fabeckstraße 34/36 14195 Berlin Germany
| | - Sebastian Riedel
- Fachbereich für Biologie, Chemie, Pharmazie Institut für Chemie und Biochemie—Anorganische Chemie Fabeckstraße 34/36 14195 Berlin Germany
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14
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Zhang Q, Lei H, Zhou CY, Wang C. Construction of N-Polyheterocycles by N-Heterocyclic Carbene Catalysis via a Regioselective Intramolecular Radical Addition/Cyclization Cascade. Org Lett 2022; 24:4615-4619. [PMID: 35731003 DOI: 10.1021/acs.orglett.2c01729] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
N-Polyheterocycles are rapidly accessed by N-heterocyclic carbene (NHC) catalysis through regioselective sequential radical addition/cyclization in the absence of any metals or oxidants. The transformation occurs under mild conditions and enjoys a wide substrate scope with excellent functional group compatibility. Furthermore, a gram-scale synthesis is also conducted. Preliminary mechanistic studies reveal the potential involvement of an NHC radical cation intermediate.
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Affiliation(s)
- Qijing Zhang
- College of Chemistry and Materials Science, Jinan University, Guangzhou, Guangdong 510632, China
| | - Hao Lei
- College of Chemistry and Materials Science, Jinan University, Guangzhou, Guangdong 510632, China
| | - Cong-Ying Zhou
- College of Chemistry and Materials Science, Jinan University, Guangzhou, Guangdong 510632, China
| | - Chengming Wang
- College of Chemistry and Materials Science, Jinan University, Guangzhou, Guangdong 510632, China.,College of Chemistry and Materials Science, Guangdong Provincial Key Laboratory of Functional Supramolecular Coordination Materials and Applications, Jinan University, Guangzhou, Guangdong 510632, China
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15
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Hoffmann KF, Battke D, Golz P, Rupf SM, Malischewski M, Riedel S. Das Tris(pentafluorophenyl)methylium‐Kation: Isolation und Reaktivität. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202203777] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Kurt F. Hoffmann
- Fachbereich für Biologie, Chemie, Pharmazie Institut für Chemie und Biochemie—Anorganische Chemie Fabeckstraße 34/36 14195 Berlin Deutschland
| | - David Battke
- Fachbereich für Biologie, Chemie, Pharmazie Institut für Chemie und Biochemie—Anorganische Chemie Fabeckstraße 34/36 14195 Berlin Deutschland
| | - Paul Golz
- Fachbereich für Biologie, Chemie, Pharmazie Institut für Chemie und Biochemie—Anorganische Chemie Fabeckstraße 34/36 14195 Berlin Deutschland
| | - Susanne M. Rupf
- Fachbereich für Biologie, Chemie, Pharmazie Institut für Chemie und Biochemie—Anorganische Chemie Fabeckstraße 34/36 14195 Berlin Deutschland
| | - Moritz Malischewski
- Fachbereich für Biologie, Chemie, Pharmazie Institut für Chemie und Biochemie—Anorganische Chemie Fabeckstraße 34/36 14195 Berlin Deutschland
| | - Sebastian Riedel
- Fachbereich für Biologie, Chemie, Pharmazie Institut für Chemie und Biochemie—Anorganische Chemie Fabeckstraße 34/36 14195 Berlin Deutschland
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16
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Maiti A, Elvers BJ, Bera S, Lindl F, Krummenacher I, Ghosh P, Braunschweig H, Yildiz CB, Schulzke C, Jana A. Disclosing Cyclic(Alkyl)(Amino)Carbenes as One‐Electron Reductants: Synthesis of Acyclic(Amino)(Aryl)Carbene‐Based Kekulé Diradicaloids. Chemistry 2022; 28:e202104567. [PMID: 35262232 PMCID: PMC9321839 DOI: 10.1002/chem.202104567] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2021] [Indexed: 11/10/2022]
Affiliation(s)
- Avijit Maiti
- Tata Institute of Fundamental Research Hyderabad Gopanpally Hyderabad 500046, Telangana India
| | - Benedict J. Elvers
- Institut für Biochemie Universität Greifswald Felix-Hausdorff-Straße 4 17489 Greifswald Germany
| | - Sachinath Bera
- Department of Chemistry Ramakrishna Mission Residential College Narendrapur Kolkata 700103 India
- Shahid Matangini Hazra Govt General Degree College for Women Tamluk Purba Medinipur 721649 India
| | - Felix Lindl
- Institute of Inorganic Chemistry and Institute for Sustainable Chemistry & Catalysis with Boron (ICB) Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Ivo Krummenacher
- Institute of Inorganic Chemistry and Institute for Sustainable Chemistry & Catalysis with Boron (ICB) Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Prasanta Ghosh
- Department of Chemistry Ramakrishna Mission Residential College Narendrapur Kolkata 700103 India
| | - Holger Braunschweig
- Institute of Inorganic Chemistry and Institute for Sustainable Chemistry & Catalysis with Boron (ICB) Julius-Maximilians-Universität Würzburg Am Hubland 97074 Würzburg Germany
| | - Cem B. Yildiz
- Department of Aromatic and Medicinal Plants Aksaray University Aksaray 68100 Turkey
| | - Carola Schulzke
- Institut für Biochemie Universität Greifswald Felix-Hausdorff-Straße 4 17489 Greifswald Germany
| | - Anukul Jana
- Tata Institute of Fundamental Research Hyderabad Gopanpally Hyderabad 500046, Telangana India
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17
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Böttcher T, Schmidlin NMC, Radtke V, Schmidt A, Lökov M, Leito I. Electronic Modification of a Sterically Demanding Anionic Pyridine Ligand. Z Anorg Allg Chem 2022. [DOI: 10.1002/zaac.202200136] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Tobias Böttcher
- Universität Freiburg Institut für Anorganische und Analytische Chemie Albertstr. 21 79104 Freiburg i.Br. GERMANY
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18
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Wu Y, Zhao Z, Chen T, Tan J, Qu Z, Grimme S, Zhao Y, Stephan DW. The Varied Frustrated Lewis Pair Reactivity of the Germylene Phosphaketene (CH{(CMe)(2,6‐
i
Pr
2
C
6
H
3
N)}
2
)GePCO. Chemistry 2022; 28:e202200666. [PMID: 35262970 PMCID: PMC9314608 DOI: 10.1002/chem.202200666] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2022] [Indexed: 01/08/2023]
Abstract
The germylene species (CH{(CMe)(2,6‐iPr2C6H3N)}2)GePCO 1 is shown to react with the Lewis acids (E(C6F5)3 E=B, Al). Nonetheless, 1 participates in FLP chemistry with electron deficient alkynes or olefins, acting as an intramolecular FLP. In contrast, in the presence of B(C6F5)3 and an electron rich alkyne, 1 behaves as Ge‐based nucleophile to effect intermolecular FLP addition to the alkyne. This reactivity demonstrates that the reaction pathway is controlled by the nature of the electrophile and nucleophile generated in solution, as revealed by extensive DFT calculations.
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Affiliation(s)
- Yile Wu
- Institute of Drug Discovery Technology Ningbo University Ningbo 315211 Zhejiang P. R. China
- State Key Laboratory of Elemento-Organic Chemistry Nankai University 30071 Tianjin P. R. China
| | - Zhao Zhao
- Institute of Drug Discovery Technology Ningbo University Ningbo 315211 Zhejiang P. R. China
| | - Ting Chen
- Institute of Drug Discovery Technology Ningbo University Ningbo 315211 Zhejiang P. R. China
| | - Jingjie Tan
- Institute of Drug Discovery Technology Ningbo University Ningbo 315211 Zhejiang P. R. China
| | - Zheng‐Wang Qu
- Mulliken Center for Theoretical Chemistry University of Bonn Beringstr. 4 53115 Bonn Germany
| | - Stefan Grimme
- Mulliken Center for Theoretical Chemistry University of Bonn Beringstr. 4 53115 Bonn Germany
| | - Yufen Zhao
- Institute of Drug Discovery Technology Ningbo University Ningbo 315211 Zhejiang P. R. China
- Department of Chemistry Xiamen University Xiamen 361005 Fujian P. R. China
| | - Douglas W. Stephan
- Institute of Drug Discovery Technology Ningbo University Ningbo 315211 Zhejiang P. R. China
- Department of Chemistry University of Toronto 80 St. George St Toronto ON M5S3H6 Canada
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19
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Liu L, Zhou CY, Wang C. Construction of highly congested quaternary carbon centers by NHC catalysis through dearomatization. GREEN SYNTHESIS AND CATALYSIS 2022. [DOI: 10.1016/j.gresc.2022.05.010] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022] Open
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20
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Abstract
Inspired by the role of N-heterocyclic carbenes (NHCs) in natural enzymatic processes, chemists have harnessed the umpolung (polarity reversal) reactivity of these reactive, Lewis basic species over the past few decades to construct key chemical bonds. While NHCs continue to play a role in two-electron transformations, their unique redox properties enable a variety of useful, stabilized radical species to be accessed via single-electron oxidation or reduction. As a result, their utility in synthesis has grown rapidly concurrent with the revival of radical chemistry, highlighted by their extensive use as reactive single-electron species in recent years.
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21
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Miller JL, Zhou L, Liu P, Floreancig PE. Mechanism-Based Approach to Reagent Selection for Oxidative Carbon-Hydrogen Bond Cleavage Reactions. Chemistry 2021; 28:e202103078. [PMID: 34822737 DOI: 10.1002/chem.202103078] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Indexed: 11/07/2022]
Abstract
Numerous hydride-abstracting agents generate the same cationic intermediate, but substrate features such as intermediate cation stability, oxidation potential, and steric environment can influence reaction rates in an oxidant-dependent manner. This manuscript provides experimental data to illustrate the role that structural features play in the kinetics of hydride abstraction reactions with commonly used quinone-, oxoammonium ion-, and carbocation- based oxidants. Computational studies of the transition state structures and energies explain these results and energy decomposition analysis calculations reveal unique sensitivities to electrostatic attraction and steric repulsions. Rigorous rate studies of select reactions validated the capacity of the calculations to predict reactivity trends. Additionally, kinetics studies demonstrate the potential for product inhibition in DDQ-mediated reactions. These studies provide a clear guide to select the optimal oxidant for structurally disparate substrates and lead to predictions of reactivity that were validated experimentally.
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Affiliation(s)
- Jenna L Miller
- Department of Chemistry, University of Pittsburgh Pittsburgh, Pennsylvania, 15260, United States
| | - Lin Zhou
- Department of Chemistry, University of Pittsburgh Pittsburgh, Pennsylvania, 15260, United States
| | - Peng Liu
- Department of Chemistry, University of Pittsburgh Pittsburgh, Pennsylvania, 15260, United States
| | - Paul E Floreancig
- Department of Chemistry, University of Pittsburgh Pittsburgh, Pennsylvania, 15260, United States
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22
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Su L, Sun H, Liu J, Wang C. Construction of Quaternary Carbon Center via NHC Catalysis Initiated by an Intermolecular Heck-Type Alkyl Radical Addition. Org Lett 2021; 23:4662-4666. [PMID: 34080869 DOI: 10.1021/acs.orglett.1c01400] [Citation(s) in RCA: 23] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
A quaternary carbon center containing an oxindole motif is constructed via NHC-catalyzed transition-metal and aldehyde-free intermolecular Heck-type alkyl radical addition initiated annulation. This redox-neutral protocol also features a simple procedure, broad substrate scope, good functional group tolerance and could be smoothly amplified to a gram scale. The mechanism study shows that the reaction possibly undergoes two folds of SET processes with an NHC radical cation intermediate involved.
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Affiliation(s)
- Lanjun Su
- School of Pharmaceutical Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Huan Sun
- School of Pharmaceutical Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Jikai Liu
- School of Pharmaceutical Sciences, South-Central University for Nationalities, Wuhan 430074, China
| | - Chengming Wang
- Department of Chemistry, College of Chemistry and Materials Science, Jinan University, Guangzhou 511443, China
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23
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Shaikh AC, Veleta JM, Moutet J, Gianetti TL. Trioxatriangulenium (TOTA +) as a robust carbon-based Lewis acid in frustrated Lewis pair chemistry. Chem Sci 2021; 12:4841-4849. [PMID: 34168760 PMCID: PMC8179643 DOI: 10.1039/d0sc05893a] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2020] [Accepted: 02/07/2021] [Indexed: 12/15/2022] Open
Abstract
We report the reactivity between the water stable Lewis acidic trioxatriangulenium ion (TOTA+) and a series of Lewis bases such as phosphines and N-heterocyclic carbene (NHC). The nature of the Lewis acid-base interaction was analyzed via variable temperature (VT) NMR spectroscopy, single-crystal X-ray diffraction, UV-visible spectroscopy, and DFT calculations. While small and strongly nucleophilic phosphines, such as PMe3, led to the formation of a Lewis acid-base adduct, frustrated Lewis pairs (FLPs) were observed for sterically hindered bases such as P( t Bu)3. The TOTA+-P( t Bu)3 FLP was characterized as an encounter complex, and found to promote the heterolytic cleavage of disulfide bonds, formaldehyde fixation, dehydrogenation of 1,4-cyclohexadiene, heterolytic cleavage of the C-Br bonds, and interception of Staudinger reaction intermediates. Moreover, TOTA+ and NHC were found to first undergo single-electron transfer (SET) to form [TOTA]·[NHC]˙+, which was confirmed via electron paramagnetic resonance (EPR) spectroscopy, and subsequently form a [TOTA-NHC]+ adduct or a mixture of products depending the reaction conditions used.
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Affiliation(s)
- Aslam C Shaikh
- University of Arizona, Department of Chemistry and Biochemistry Tucson AZ USA
| | - José M Veleta
- University of Arizona, Department of Chemistry and Biochemistry Tucson AZ USA
| | - Jules Moutet
- University of Arizona, Department of Chemistry and Biochemistry Tucson AZ USA
| | - Thomas L Gianetti
- University of Arizona, Department of Chemistry and Biochemistry Tucson AZ USA
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24
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Dasgupta A, Richards E, Melen RL. Frustrated Radical Pairs: Insights from EPR Spectroscopy. Angew Chem Int Ed Engl 2021; 60:53-65. [PMID: 32931604 PMCID: PMC7883636 DOI: 10.1002/anie.202010633] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2020] [Indexed: 12/29/2022]
Abstract
Progress in frustrated Lewis pair (FLP) chemistry has revealed the importance of the main group elements in catalysis, opening new avenues in synthetic chemistry. Recently, new reactivities of frustrated Lewis pairs have been uncovered that disclose that certain combinations of Lewis acids and bases undergo single-electron transfer (SET) processes. Here an electron can be transferred from the Lewis basic donor to a Lewis acidic acceptor to generate a reactive frustrated radical pair (FRP). This minireview aims to showcase the recent advancements in this emerging field covering the synthesis and reactivities of frustrated radical pairs, with extensive highlights of the results from Electron Paramagnetic Resonance (EPR) spectroscopy to explain the nature and stability of the different radical species observed.
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Affiliation(s)
- Ayan Dasgupta
- School of ChemistryCardiff Catalysis InstituteCardiff UniversityMain Building, Park PlaceCardiffCF10 3ATUK
| | - Emma Richards
- School of ChemistryCardiff Catalysis InstituteCardiff UniversityMain Building, Park PlaceCardiffCF10 3ATUK
| | - Rebecca L. Melen
- School of ChemistryCardiff Catalysis InstituteCardiff UniversityMain Building, Park PlaceCardiffCF10 3ATUK
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25
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Abstract
A NHC-catalyzed metal-free oxindole synthesis method is developed.
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Affiliation(s)
- Chengming Wang
- Department of Chemistry
- College of Chemistry and Materials Science
- Jinan University
- Guangzhou
- China
| | - Lixia Liu
- Department of Chemistry
- College of Chemistry and Materials Science
- Jinan University
- Guangzhou
- China
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26
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Pan Y, Cui J, Wei Y, Xu Z, Wang T. B-H and O-H bonds activation via a single electron transfer of frustrated radical pairs. Dalton Trans 2021; 50:8947-8954. [PMID: 34109966 DOI: 10.1039/d1dt01169c] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The rare examples of B-H bond activation in a frustrated radical pair regime have been observed by treatment of TEMPO radicals with Piers' borane HB(C6F5)2 or bis-borane, respectively. The resulting concomitant formation of zwitterionic products and geminal N/B frustrated Lewis pairs implied a one electron process. In addition, the reaction of a TEMPO/B(C6F5)3 pair with H2O·B(C6F5)3 was assumed to involve one-electron reduction of water. Our results provide insights into chemical bond (e.g. B-H and O-H) activation via a single electron transfer.
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Affiliation(s)
- Yanlin Pan
- Zhang Dayu School of Chemistry, Dalian University of Technology, Dalian 116024, P. R. China.
| | - Jie Cui
- Zhang Dayu School of Chemistry, Dalian University of Technology, Dalian 116024, P. R. China.
| | - Yongliang Wei
- Zhang Dayu School of Chemistry, Dalian University of Technology, Dalian 116024, P. R. China.
| | - Zhaochao Xu
- Zhang Dayu School of Chemistry, Dalian University of Technology, Dalian 116024, P. R. China. and CAS Key Laboratory of Separation Science for Analytical Chemistry, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian 116023, China
| | - Tongdao Wang
- Zhang Dayu School of Chemistry, Dalian University of Technology, Dalian 116024, P. R. China.
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27
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Holtrop F, Jupp AR, Kooij BJ, van Leest NP, de Bruin B, Slootweg JC. Single-Electron Transfer in Frustrated Lewis Pair Chemistry. Angew Chem Int Ed Engl 2020; 59:22210-22216. [PMID: 32840947 PMCID: PMC7756365 DOI: 10.1002/anie.202009717] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Indexed: 02/05/2023]
Abstract
Frustrated Lewis pairs (FLPs) are well known for their ability to activate small molecules. Recent reports of radical formation within such systems indicate single-electron transfer (SET) could play an important role in their chemistry. Herein, we investigate radical formation upon reacting FLP systems with dihydrogen, triphenyltin hydride, or tetrachloro-1,4-benzoquinone (TCQ) both experimentally and computationally to determine the nature of the single-electron transfer (SET) events; that is, being direct SET to B(C6 F5 )3 or not. The reactions of H2 and Ph3 SnH with archetypal P/B FLP systems do not proceed via a radical mechanism. In contrast, reaction with TCQ proceeds via SET, which is only feasible by Lewis acid coordination to the substrate. Furthermore, SET from the Lewis base to the Lewis acid-substrate adduct may be prevalent in other reported examples of radical FLP chemistry, which provides important design principles for radical main-group chemistry.
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Affiliation(s)
- Flip Holtrop
- Van't Hoff Institute for Molecular SciencesUniversity of AmsterdamPO Box 941571090 GDAmsterdamThe Netherlands
| | - Andrew R. Jupp
- Van't Hoff Institute for Molecular SciencesUniversity of AmsterdamPO Box 941571090 GDAmsterdamThe Netherlands
| | - Bastiaan J. Kooij
- Van't Hoff Institute for Molecular SciencesUniversity of AmsterdamPO Box 941571090 GDAmsterdamThe Netherlands
| | - Nicolaas P. van Leest
- Van't Hoff Institute for Molecular SciencesUniversity of AmsterdamPO Box 941571090 GDAmsterdamThe Netherlands
| | - Bas de Bruin
- Van't Hoff Institute for Molecular SciencesUniversity of AmsterdamPO Box 941571090 GDAmsterdamThe Netherlands
| | - J. Chris Slootweg
- Van't Hoff Institute for Molecular SciencesUniversity of AmsterdamPO Box 941571090 GDAmsterdamThe Netherlands
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28
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Dasgupta A, Richards E, Melen RL. Frustrated Radical Pairs: Insights from EPR Spectroscopy. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202010633] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Affiliation(s)
- Ayan Dasgupta
- School of Chemistry Cardiff Catalysis Institute Cardiff University Main Building, Park Place Cardiff CF10 3AT UK
| | - Emma Richards
- School of Chemistry Cardiff Catalysis Institute Cardiff University Main Building, Park Place Cardiff CF10 3AT UK
| | - Rebecca L. Melen
- School of Chemistry Cardiff Catalysis Institute Cardiff University Main Building, Park Place Cardiff CF10 3AT UK
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29
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Holtrop F, Jupp AR, Kooij BJ, Leest NP, Bruin B, Slootweg JC. Single‐Electron Transfer in Frustrated Lewis Pair Chemistry. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202009717] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Affiliation(s)
- Flip Holtrop
- Van't Hoff Institute for Molecular Sciences University of Amsterdam PO Box 94157 1090 GD Amsterdam The Netherlands
| | - Andrew R. Jupp
- Van't Hoff Institute for Molecular Sciences University of Amsterdam PO Box 94157 1090 GD Amsterdam The Netherlands
| | - Bastiaan J. Kooij
- Van't Hoff Institute for Molecular Sciences University of Amsterdam PO Box 94157 1090 GD Amsterdam The Netherlands
| | - Nicolaas P. Leest
- Van't Hoff Institute for Molecular Sciences University of Amsterdam PO Box 94157 1090 GD Amsterdam The Netherlands
| | - Bas Bruin
- Van't Hoff Institute for Molecular Sciences University of Amsterdam PO Box 94157 1090 GD Amsterdam The Netherlands
| | - J. Chris Slootweg
- Van't Hoff Institute for Molecular Sciences University of Amsterdam PO Box 94157 1090 GD Amsterdam The Netherlands
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30
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Cicač-Hudi M, Feil CM, Birchall N, Nieger M, Gudat D. Proton transfer vs. oligophosphine formation by P–C/P–H σ-bond metathesis: decoding the competing Brønsted and Lewis type reactivities of imidazolio-phosphines. Dalton Trans 2020; 49:17401-17413. [DOI: 10.1039/d0dt03633a] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Cationic imidazolio-phosphines show two-sided reactivity towards bases, undergoing either Brønsted-type proton transfer to imidazolio-phosphides or autocatalytic Lewis acid/base reaction cascades to yield P-free imidazolium ions and oligophosphines.
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Affiliation(s)
- Mario Cicač-Hudi
- Institute of Inorganic Chemistry
- University of Stuttgart
- 70550 Stuttgart
- Germany
| | - Christoph M. Feil
- Institute of Inorganic Chemistry
- University of Stuttgart
- 70550 Stuttgart
- Germany
| | - Nicholas Birchall
- Institute of Inorganic Chemistry
- University of Stuttgart
- 70550 Stuttgart
- Germany
| | - Martin Nieger
- Department of Chemistry
- University of Helsinki
- 00014 Helsinki
- Finland
| | - Dietrich Gudat
- Institute of Inorganic Chemistry
- University of Stuttgart
- 70550 Stuttgart
- Germany
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