1
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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: 10] [Impact Index Per Article: 10.0] [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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2
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Mears KL, Kutzleb MA, Stennett CR, Fettinger JC, Kaseman DC, Yu P, Vasko P, Power PP. Terpene dispersion energy donor ligands in borane complexes. Chem Commun (Camb) 2022; 58:9910-9913. [PMID: 35979664 DOI: 10.1039/d2cc04203g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Structural characterization of the complex [B(β-pinane)3] (1) reveals non-covalent H⋯H contacts that are consistent with the generation of London dispersion energies involving the β-pinane ligand frameworks. The homolytic fragmentations of 1, and camphane and sabinane analogues ([B(camphane)3] (2) and [B(sabinane)3] (3)) were studied computationally. Isodesmic exchange results showed that London dispersion interactions are highly dependent on the terpene's stereochemistry, with the β-pinane framework providing the greatest dispersion free energy (ΔG = -7.9 kcal mol-1) with Grimme's dispersion correction (D3BJ) employed. PMe3 was used to coordinate to [B(β-pinane)3], giving the complex [Me3P-B(β-pinane)3] (4), which displayed a dynamic coordination equilibrium in solution. The association process was found to be slightly endergonic at 302 K (ΔG = +0.29 kcal mol-1).
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Affiliation(s)
- Kristian L Mears
- Department of Chemistry, University of California, One Shields Avenue, Davis, CA 95616, USA.
| | - Michelle A Kutzleb
- Department of Chemistry, University of California, One Shields Avenue, Davis, CA 95616, USA.
| | - Cary R Stennett
- Department of Chemistry, University of California, One Shields Avenue, Davis, CA 95616, USA.
| | - James C Fettinger
- Department of Chemistry, University of California, One Shields Avenue, Davis, CA 95616, USA.
| | - Derrick C Kaseman
- Department of Chemistry, University of California, One Shields Avenue, Davis, CA 95616, USA.
| | - Ping Yu
- Department of Chemistry, University of California, One Shields Avenue, Davis, CA 95616, USA.
| | - Petra Vasko
- Department of Chemistry, University of Helsinki, PO Box 55 (A. I. Virtasen aukio 1), 00014, Finland.
| | - Philip P Power
- Department of Chemistry, University of California, One Shields Avenue, Davis, CA 95616, USA.
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3
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Micheletti G, Mayer RJ, Cino S, Boga C, Mazzanti A, Ofial AR, Mayr H. Quantification of the Lewis Basicities and Nucleophilicities of 1,3,5‐Tris(dialkylamino)benzenes. European J Org Chem 2021. [DOI: 10.1002/ejoc.202100939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Gabriele Micheletti
- Department of Industrial Chemistry ‘Toso Montanari' Alma Mater Studiorum – Università di Bologna Viale Risorgimento 4 40136 Bologna Italy
| | - Robert J. Mayer
- Department Chemie Ludwig-Maximilians-Universität München Butenandtstr. 5–13 81377 München Germany
| | - Silvia Cino
- Department of Industrial Chemistry ‘Toso Montanari' Alma Mater Studiorum – Università di Bologna Viale Risorgimento 4 40136 Bologna Italy
| | - Carla Boga
- Department of Industrial Chemistry ‘Toso Montanari' Alma Mater Studiorum – Università di Bologna Viale Risorgimento 4 40136 Bologna Italy
| | - Andrea Mazzanti
- Department of Industrial Chemistry ‘Toso Montanari' Alma Mater Studiorum – Università di Bologna Viale Risorgimento 4 40136 Bologna Italy
| | - Armin R. Ofial
- Department Chemie Ludwig-Maximilians-Universität München Butenandtstr. 5–13 81377 München Germany
| | - Herbert Mayr
- Department Chemie Ludwig-Maximilians-Universität München Butenandtstr. 5–13 81377 München Germany
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4
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Dasgupta A, Stefkova K, Babaahmadi R, Yates BF, Buurma NJ, Ariafard A, Richards E, Melen RL. Site-Selective C sp3-C sp/C sp3-C sp2 Cross-Coupling Reactions Using Frustrated Lewis Pairs. J Am Chem Soc 2021; 143:4451-4464. [PMID: 33719443 PMCID: PMC8041292 DOI: 10.1021/jacs.1c01622] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2021] [Indexed: 02/08/2023]
Abstract
The donor-acceptor ability of frustrated Lewis pairs (FLPs) has led to widespread applications in organic synthesis. Single electron transfer from a donor Lewis base to an acceptor Lewis acid can generate a frustrated radical pair (FRP) depending on the substrate and energy required (thermal or photochemical) to promote an FLP into an FRP system. Herein, we report the Csp3-Csp cross-coupling reaction of aryl esters with terminal alkynes using the B(C6F5)3/Mes3P FLP. Significantly, when the 1-ethynyl-4-vinylbenzene substrate was employed, the exclusive formation of Csp3-Csp cross-coupled products was observed. However, when 1-ethynyl-2-vinylbenzene was employed, solvent-dependent site-selective Csp3-Csp or Csp3-Csp2 cross-coupling resulted. The nature of these reaction pathways and their selectivity has been investigated by extensive electron paramagnetic resonance (EPR) studies, kinetic studies, and density functional theory (DFT) calculations both to elucidate the mechanism of these coupling reactions and to explain the solvent-dependent site selectivity.
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Affiliation(s)
- Ayan Dasgupta
- Cardiff
Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, Cymru/Wales, United Kingdom
| | - Katarina Stefkova
- Cardiff
Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, Cymru/Wales, United Kingdom
| | - Rasool Babaahmadi
- School
of Natural Sciences-Chemistry, University
of Tasmania Private Bag 75, Hobart, Tasmania 7001, Australia
| | - Brian F. Yates
- School
of Natural Sciences-Chemistry, University
of Tasmania Private Bag 75, Hobart, Tasmania 7001, Australia
| | - Niklaas J. Buurma
- Cardiff
Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, Cymru/Wales, United Kingdom
| | - Alireza Ariafard
- School
of Natural Sciences-Chemistry, University
of Tasmania Private Bag 75, Hobart, Tasmania 7001, Australia
| | - Emma Richards
- Cardiff
Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, Cymru/Wales, United Kingdom
| | - Rebecca L. Melen
- Cardiff
Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff CF10 3AT, Cymru/Wales, United Kingdom
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5
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Mayer RJ, Hampel N, Ofial AR. Lewis Acidic Boranes, Lewis Bases, and Equilibrium Constants: A Reliable Scaffold for a Quantitative Lewis Acidity/Basicity Scale. Chemistry 2021; 27:4070-4080. [PMID: 33215760 PMCID: PMC7985883 DOI: 10.1002/chem.202003916] [Citation(s) in RCA: 28] [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: 08/25/2020] [Indexed: 12/15/2022]
Abstract
A quantitative Lewis acidity/basicity scale toward boron-centered Lewis acids has been developed based on a set of 90 experimental equilibrium constants for the reactions of triarylboranes with various O-, N-, S-, and P-centered Lewis bases in dichloromethane at 20 °C. Analysis with the linear free energy relationship log KB =LAB +LBB allows equilibrium constants, KB , to be calculated for any type of borane/Lewis base combination through the sum of two descriptors, one for Lewis acidity (LAB ) and one for Lewis basicity (LBB ). The resulting Lewis acidity/basicity scale is independent of fixed reference acids/bases and valid for various types of trivalent boron-centered Lewis acids. It is demonstrated that the newly developed Lewis acidity/basicity scale is easily extendable through linear relationships with quantum-chemically calculated or common physical-organic descriptors and known thermodynamic data (ΔHBF 3 ). Furthermore, this experimental platform can be utilized for the rational development of borane-catalyzed reactions.
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Affiliation(s)
- Robert J. Mayer
- Department ChemieLudwig-Maximilians-Universität MünchenButenandtstr. 5–1381377MünchenGermany
| | - Nathalie Hampel
- Department ChemieLudwig-Maximilians-Universität MünchenButenandtstr. 5–1381377MünchenGermany
| | - Armin R. Ofial
- Department ChemieLudwig-Maximilians-Universität MünchenButenandtstr. 5–1381377MünchenGermany
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6
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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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7
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Li J, Luo Y. The correct assignment of vibrationally-resolved absorption spectra of protonated anthracene isomers. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2021; 244:118832. [PMID: 32871391 DOI: 10.1016/j.saa.2020.118832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2020] [Revised: 07/31/2020] [Accepted: 08/09/2020] [Indexed: 06/11/2023]
Abstract
The assignment of experimental optical absorption spectra of protonated anthracene has been under debate for years. It is complicated by the presence of rich vibronic spectral features and the possible co-occurrence of two isomers, 9H-An+ and 1H-An+. In this study, the vibrationally resolved absorption spectra of 9H-An+ and 1H-An+ have been calculated using time-dependent density functional theory. The calculated vibronic spectra profiles of 9H-An+ and 1H-An+ are in excellent agreement with the corresponding experimental results and provide unambiguously spectra assignments. It shows that the previously reported assignments based on vertical excitation energy are largely wrong. The onset located at 493.8 nm of the experimental spectrum can be assigned to the S0 → S1 transition of 9H-An+, while the origin band located at 453.5 nm corresponds to the S0 → S2 transition of 1H-An+.
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Affiliation(s)
- Junfeng Li
- College of Chemistry and Chemical Engineering, and Henan Key Laboratory of Function-Oriented Porous Materials, Luoyang Normal University, 471934 Luoyang, PR China; Department of Theoretical Chemistry and Biology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, S-106 91 Stockholm, Sweden.
| | - Yi Luo
- Department of Theoretical Chemistry and Biology, School of Engineering Sciences in Chemistry, Biotechnology and Health, KTH Royal Institute of Technology, S-106 91 Stockholm, Sweden; Hefei National Laboratory for Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, Anhui, PR China
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8
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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: 40] [Impact Index Per Article: 13.3] [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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9
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Yolsal U, Horton TA, Wang M, Shaver MP. Polymer-supported Lewis acids and bases: Synthesis and applications. Prog Polym Sci 2020. [DOI: 10.1016/j.progpolymsci.2020.101313] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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10
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Li CJ, Ung SPM, Mechrouk VA. Shining Light on the Light-Bearing Element: A Brief Review of Photomediated C–H Phosphorylation Reactions. SYNTHESIS-STUTTGART 2020. [DOI: 10.1055/s-0040-1705978] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
AbstractOrganophosphorus compounds have numerous useful applications, from versatile ligands and nucleophiles in the case of trivalent organophosphorus species to therapeutics, agrochemicals and material additives for pentavalent species. Although phosphorus chemistry is a fairly mature field, the construction of C–P(V) bonds relies heavily on either prefunctionalized substrates such as alkyl or aryl halides, or requires previously oxidized bonds such as C=N or C=O, leading to potential sustainability issues when looking at the overall synthetic route. In light of the recent advances in photochemistry, using photons as a reagent can provide better alternatives for phosphorylations by unlocking radical mechanisms and providing interesting redox pathways. This review will showcase the different photomediated phosphorylation procedures available for converting C–H bonds into C–P(V) bonds.1 Introduction1.1 Organophosphorus Compounds1.2 Phosphorylation: Construction of C–P(V) Bonds1.3 Photochemistry as an Alternative to Classical Phosphorylations2 Ionic Mechanisms Involving Nucleophilic Additions3 Mechanisms Involving Radical Intermediates3.1 Mechanisms Involving Reactive Carbon Radicals3.2 Mechanisms Involving Phosphorus Radicals3.2.1 Photoredox: Direct Creation of Phosphorus Radicals3.2.2 Photoredox: Indirect Creation of Phosphorus Radicals3.2.3 Dual Catalysis3.3 Photolytic Cleavage4 Conclusion and Outlook
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11
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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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12
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Mandal D, Stein F, Chandra S, Neuman NI, Sarkar P, Das S, Kundu A, Sarkar A, Rawat H, Pati SK, Chandrasekhar V, Sarkar B, Jana A. Trisubstituted geminal diazaalkene derived transient 1,2-carbodications. Chem Commun (Camb) 2020; 56:8233-8236. [PMID: 32558832 DOI: 10.1039/d0cc02807j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The coulombic repulsion between two adjacent cation centres of 1,2-carbodications is known to decrease with π- and/or n-donor substituents by a positive charge delocalization. Here we report the delocalization of the positive charge of transient 1,2-carbodications having one H-substituent by an intramolecular base-coordination. N-heterocyclic olefin (NHO) derived 2-pyrrolidinyl appended trisubstituted geminal diazaalkenes were used for the generation of transient 1,2-carbodications through a 2-e chemical oxidation process. We have also studied the 1-e oxidation reaction of trisubstituted geminal diazaalkenes (electrochemically and chemically) and also studied them using in situ EPR spectroscopy.
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Affiliation(s)
- Debdeep Mandal
- Tata Institute of Fundamental Research Hyderabad, Gopanpally, Hyderabad 500107, Telangana, India.
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13
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Shaikh AC, Veleta JM, Bloch J, Goodman HJ, Gianetti TL. Syntheses of Phosphonium Salts from Phosphines and Carbenium: Efficient CO2
Fixation and Phase-Transfer Catalysts. European J Org Chem 2020. [DOI: 10.1002/ejoc.202000221] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- Aslam C. Shaikh
- Department of Chemistry and Biochemistry; University of Arizona; 1306 E. University Blvd. 85719 Tucson AZ USA
| | - José M. Veleta
- Department of Chemistry and Biochemistry; University of Arizona; 1306 E. University Blvd. 85719 Tucson AZ USA
| | - Jan Bloch
- Department of Chemistry and Applied Biosciences; ETH Zürich; Vladimir-Prelog-Weg 1 8093 Zürich Switzerland
| | - Hannah J. Goodman
- Department of Chemistry and Biochemistry; University of Arizona; 1306 E. University Blvd. 85719 Tucson AZ USA
| | - Thomas L. Gianetti
- Department of Chemistry and Biochemistry; University of Arizona; 1306 E. University Blvd. 85719 Tucson AZ USA
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14
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Heskia A, Maris T, Aguiar PM, Wuest JD. Building Large Structures with Curved Aromatic Surfaces by Complexing Metals with Phosphangulene. J Am Chem Soc 2019; 141:18740-18753. [DOI: 10.1021/jacs.9b08179] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Alice Heskia
- Département de Chimie, Université de Montréal, Montréal, Québec H3C 3J7 Canada
| | - Thierry Maris
- Département de Chimie, Université de Montréal, Montréal, Québec H3C 3J7 Canada
| | - Pedro M. Aguiar
- Département de Chimie, Université de Montréal, Montréal, Québec H3C 3J7 Canada
| | - James D. Wuest
- Département de Chimie, Université de Montréal, Montréal, Québec H3C 3J7 Canada
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15
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Hu L, Mahaut D, Tumanov N, Wouters J, Robiette R, Berionni G. Complementary Synthetic Approaches toward 9-Phosphatriptycene and Structure-Reactivity Investigations of Its Association with Sterically Hindered Lewis Acids. J Org Chem 2019; 84:11268-11274. [PMID: 31385508 DOI: 10.1021/acs.joc.9b01570] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Two practical and high-yielding syntheses of 9-phosphatriptycene are reported. In both approaches, the key step is based on the cyclization of a (tris)lithio-triphenylmethane or a (tris)lithio-triphenylphosphine intermediate on a phosphorus or a carbon electrophile, respectively. The association of 9-phosphatriptycene with representative boron- and carbon-centered Lewis acids was investigated by IR, NMR, and UV-vis titration experiments and by computational methods, shedding light on its steric hindrance, σ-donating ability, and Brønsted and Lewis basicities.
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Affiliation(s)
- Lei Hu
- Department of Chemistry, Namur Institute of Structured Matter , University of Namur , rue de Bruxelles 61 , 5000 Namur , Belgium.,Institute of Condensed Matter and Nanosciences , Université catholique de Louvain , Place Louis Pasteur 1 Box L4.01.02 , 1348 Louvain-la-Neuve , Belgium
| | - Damien Mahaut
- Department of Chemistry, Namur Institute of Structured Matter , University of Namur , rue de Bruxelles 61 , 5000 Namur , Belgium
| | - Nikolay Tumanov
- Department of Chemistry, Namur Institute of Structured Matter , University of Namur , rue de Bruxelles 61 , 5000 Namur , Belgium
| | - Johan Wouters
- Department of Chemistry, Namur Institute of Structured Matter , University of Namur , rue de Bruxelles 61 , 5000 Namur , Belgium
| | - Raphaël Robiette
- Institute of Condensed Matter and Nanosciences , Université catholique de Louvain , Place Louis Pasteur 1 Box L4.01.02 , 1348 Louvain-la-Neuve , Belgium
| | - Guillaume Berionni
- Department of Chemistry, Namur Institute of Structured Matter , University of Namur , rue de Bruxelles 61 , 5000 Namur , Belgium
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16
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Mandal D, Sobottka S, Dolai R, Maiti A, Dhara D, Kalita P, Narayanan RS, Chandrasekhar V, Sarkar B, Jana A. Direct access to 2-aryl substituted pyrrolinium salts for carbon centre based radicals without pyrrolidine-2-ylidene alias cyclic(alkyl)(amino)carbene (CAAC) as a precursor. Chem Sci 2019; 10:4077-4081. [PMID: 31049189 PMCID: PMC6470959 DOI: 10.1039/c8sc05477k] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2018] [Accepted: 02/27/2019] [Indexed: 12/20/2022] Open
Abstract
A new strategy to synthesise 2-substituted pyrrolinium salts.
The synthesis of organic radicals is challenging due to their inherent instability. In recent years, cyclic(alkyl)(amino)carbene (CAAC)-derived 2-substituted pyrrolinium salts have been used as synthons for the synthesis of isolable carbon-based radicals. Herein, we report a direct, easy and convenient method for the synthesis of 2-aryl substituted pyrrolinium salts without using CAAC as a precursor. These cations can be reduced to the corresponding radicals. The influence of the aryl substituent at the C-2 position on radical stabilization and dimerization has been investigated. Because of the large scope of our strategy (capability to modulate different substituents at all the C- and N-centres of the pyrrolinium salts), it has the merit to be an extremely effective and productive route for generating carbon-based radicals whose stability as well as reactivity can be varied.
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Affiliation(s)
- Debdeep Mandal
- Tata Institute of Fundamental Research Hyderabad , Gopanpally , Hyderabad-500107 , Telangana , India .
| | - Sebastian Sobottka
- Institut für Chemie und Biochemie, Anorganische Chemie , Freie Universität Berlin , Fabeckstraße 34-36 , 14195 , Berlin , Germany .
| | - Ramapada Dolai
- Tata Institute of Fundamental Research Hyderabad , Gopanpally , Hyderabad-500107 , Telangana , India .
| | - Avijit Maiti
- Tata Institute of Fundamental Research Hyderabad , Gopanpally , Hyderabad-500107 , Telangana , India .
| | - Debabrata Dhara
- Tata Institute of Fundamental Research Hyderabad , Gopanpally , Hyderabad-500107 , Telangana , India .
| | - Pankaj Kalita
- School of Chemical Sciences , National Institute of Science Education and Research , HBNI , Bhubaneswar-752050 , India
| | | | - Vadapalli Chandrasekhar
- Tata Institute of Fundamental Research Hyderabad , Gopanpally , Hyderabad-500107 , Telangana , India . .,Department of Chemistry , Indian Institute of Technology Kanpur , Kanpur-208016 , India .
| | - Biprajit Sarkar
- Institut für Chemie und Biochemie, Anorganische Chemie , Freie Universität Berlin , Fabeckstraße 34-36 , 14195 , Berlin , Germany .
| | - Anukul Jana
- Tata Institute of Fundamental Research Hyderabad , Gopanpally , Hyderabad-500107 , Telangana , India .
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Merk A, Großekappenberg H, Schmidtmann M, Luecke M, Lorent C, Driess M, Oestreich M, Klare HFT, Müller T. Einelektronenübertragungsreaktionen in frustrierten und klassischen Silyliumion/Phosphan‐Lewis‐Paaren. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201808922] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Anastasia Merk
- Institut für ChemieCarl von Ossietzky Universität Oldenburg Carl von Ossietzky-Straße 9–11 26129 Oldenburg Deutschland
| | - Henning Großekappenberg
- Institut für ChemieCarl von Ossietzky Universität Oldenburg Carl von Ossietzky-Straße 9–11 26129 Oldenburg Deutschland
| | - Marc Schmidtmann
- Institut für ChemieCarl von Ossietzky Universität Oldenburg Carl von Ossietzky-Straße 9–11 26129 Oldenburg Deutschland
| | - Marcel‐Philip Luecke
- Institut für ChemieTechnische Universität Berlin Straße des 17. Juni 115 10623 Berlin Deutschland
| | - Christian Lorent
- Institut für ChemieTechnische Universität Berlin Straße des 17. Juni 115 10623 Berlin Deutschland
| | - Matthias Driess
- Institut für ChemieTechnische Universität Berlin Straße des 17. Juni 115 10623 Berlin Deutschland
| | - Martin Oestreich
- Institut für ChemieTechnische Universität Berlin Straße des 17. Juni 115 10623 Berlin Deutschland
| | - Hendrik F. T. Klare
- Institut für ChemieTechnische Universität Berlin Straße des 17. Juni 115 10623 Berlin Deutschland
| | - Thomas Müller
- Institut für ChemieCarl von Ossietzky Universität Oldenburg Carl von Ossietzky-Straße 9–11 26129 Oldenburg Deutschland
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18
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Merk A, Großekappenberg H, Schmidtmann M, Luecke MP, Lorent C, Driess M, Oestreich M, Klare HFT, Müller T. Single-Electron Transfer Reactions in Frustrated and Conventional Silylium Ion/Phosphane Lewis Pairs. Angew Chem Int Ed Engl 2018; 57:15267-15271. [PMID: 30178534 DOI: 10.1002/anie.201808922] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Revised: 08/31/2018] [Indexed: 01/08/2023]
Abstract
Silylium ions undergo a single-electron reduction with phosphanes, leading to transient silyl radicals and the corresponding stable phosphoniumyl radical cations. As supported by DFT calculations, phosphanes with electron-rich 2,6-disubstituted aryl groups are sufficiently strong reductants to facilitate this single-electron transfer (SET). Frustration as found in kinetically stabilized triarylsilylium ion/phosphane Lewis pairs is not essential, and silylphosphonium ions, which are generated by conventional Lewis adduct formation of solvent-stabilized trialkylsilylium ions and phosphanes, engage in the same radical mechanism. The trityl cation, a Lewis acid with a higher electron affinity, even oxidizes trialkylphosphanes, such as tBu3 P, which does not react with either B(C6 F5 )3 or silylium ions.
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Affiliation(s)
- Anastasia Merk
- Institut für Chemie, Carl von Ossietzky Universität Oldenburg, Carl von Ossietzky-Strasse 9-11, 26129, Oldenburg, Germany
| | - Henning Großekappenberg
- Institut für Chemie, Carl von Ossietzky Universität Oldenburg, Carl von Ossietzky-Strasse 9-11, 26129, Oldenburg, Germany
| | - Marc Schmidtmann
- Institut für Chemie, Carl von Ossietzky Universität Oldenburg, Carl von Ossietzky-Strasse 9-11, 26129, Oldenburg, Germany
| | - Marcel-Philip Luecke
- Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 115, 10623, Berlin, Germany
| | - Christian Lorent
- Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 115, 10623, Berlin, Germany
| | - Matthias Driess
- Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 115, 10623, Berlin, Germany
| | - Martin Oestreich
- Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 115, 10623, Berlin, Germany
| | - Hendrik F T Klare
- Institut für Chemie, Technische Universität Berlin, Strasse des 17. Juni 115, 10623, Berlin, Germany
| | - Thomas Müller
- Institut für Chemie, Carl von Ossietzky Universität Oldenburg, Carl von Ossietzky-Strasse 9-11, 26129, Oldenburg, Germany
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19
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Schmauck J, Breugst M. The potential of pnicogen bonding for catalysis - a computational study. Org Biomol Chem 2018; 15:8037-8045. [PMID: 28770945 DOI: 10.1039/c7ob01599b] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Pnicogen bonding is a noncovalent interaction between the electrophilic region of a phosphorus atom and a Lewis base. Although this interaction can be comparable in strength to other noncovalent interactions, no systematic application in organic synthesis or catalysis is known so far. To identify the potential of this interaction for organocatalysis, we have now analysed different pnicogen-bond donors as catalysts for the activation of three different model reactions employing density functional theory. Our calculations suggest rate accelerations of several orders of magnitude for all cases indicating that synthetic applications should be feasible. Furthermore, our results indicate that pnicogen-bond donors can be comparable to halogen-bond-based catalysts in these reactions.
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Affiliation(s)
- J Schmauck
- Universität zu Köln, Department für Chemie, Greinstraße 4, 50939 Köln, Germany.
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20
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Zhou J, Cao LL, Liu LL, Stephan DW. FLP reactivity of [Ph 3C] + and (o-tolyl) 3P and the capture of a Staudinger reaction intermediate. Dalton Trans 2017; 46:9334-9338. [PMID: 28548663 DOI: 10.1039/c7dt01726j] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The frustrated Lewis pair (FLP) derived from the trityl cation and (o-tolyl)3P effects the activation of 1,4-cyclohexadiene and 1-bromo-4-ethynylbenzene and heterolytically cleaves the S-S bond of diphenyl disulfide. The FLP also captures pentafluorophenyl azide as the Staudinger reaction intermediate, a species that reacts with Ph3SiH to give the silyl analog.
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Affiliation(s)
- Jiliang Zhou
- Department of Chemistry, University of Toronto, 80 St George St., Toronto, Ontario M5S 3H6, Canada.
| | - Levy L Cao
- Department of Chemistry, University of Toronto, 80 St George St., Toronto, Ontario M5S 3H6, Canada.
| | - Liu Leo Liu
- Department of Chemistry, University of Toronto, 80 St George St., Toronto, Ontario M5S 3H6, Canada.
| | - Douglas W Stephan
- Department of Chemistry, University of Toronto, 80 St George St., Toronto, Ontario M5S 3H6, Canada.
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21
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Fasano V, Curless LD, Radcliffe JE, Ingleson MJ. Frustrated Lewis Pair Mediated 1,2-Hydrocarbation of Alkynes. Angew Chem Int Ed Engl 2017; 56:9202-9206. [PMID: 28608991 PMCID: PMC5577509 DOI: 10.1002/anie.201705100] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Indexed: 01/26/2023]
Abstract
Frustrated Lewis pair (FLP) chemistry enables a rare example of alkyne 1,2-hydrocarbation with N-methylacridinium salts as the carbon Lewis acid. This 1,2-hydrocarbation process does not proceed through a concerted mechanism as in alkyne syn-hydroboration, or through an intramolecular 1,3-hydride migration as operates in the only other reported alkyne 1,2-hydrocarbation reaction. Instead, in this study, alkyne 1,2-hydrocarbation proceeds by a novel mechanism involving alkyne dehydrocarbation with a carbon Lewis acid based FLP to form the new C-C bond. Subsequently, intermolecular hydride transfer occurs, with the Lewis acid component of the FLP acting as a hydride shuttle that enables alkyne 1,2-hydrocarbation.
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Affiliation(s)
- Valerio Fasano
- School of ChemistryUniversity of ManchesterOxford RoadManchesterM13 9PLUK
| | - Liam D. Curless
- School of ChemistryUniversity of ManchesterOxford RoadManchesterM13 9PLUK
| | - James E. Radcliffe
- School of ChemistryUniversity of ManchesterOxford RoadManchesterM13 9PLUK
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22
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Issaian A, Faizi DJ, Bailey JO, Mayer P, Berionni G, Singleton DA, Blum SA. Mechanistic Studies of Formal Thioboration Reactions of Alkynes. J Org Chem 2017; 82:8165-8178. [PMID: 28671461 DOI: 10.1021/acs.joc.7b01500] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Several formal heteroborylative cyclization reactions have been recently reported, but little physical-organic and mechanistic data are known. We now investigate the catalyst-free formal thioboration reaction of alkynes to gain mechanistic insight into B-chlorocatecholborane (ClBcat) in its new role as an alkynophilic Lewis acid in electrophilic cyclization/dealkylation reactions. In kinetic studies, the reaction is second-order globally and first-order with respect to both the 2-alkynylthioanisole substrate and the ClBcat electrophile, with activation parameters of ΔG‡ = 27.1 ± 0.1 kcal mol-1 at 90 °C, ΔH‡ = 13.8 ± 1.0 kcal mol-1, and ΔS‡ = -37 ± 3 cal mol-1 K-1, measured over the range 70-90 °C. Carbon kinetic isotope effects supported a rate-determining AdE3 mechanism wherein alkyne activation by neutral ClBcat is concerted with cyclative attack by nucleophilic sulfur. A Hammett study found a ρ+ of -1.7, suggesting cationic charge buildup during the cyclization and supporting rate-determining concerted cyclization. Studies of the reaction with tris(pentafluorophenyl)borane (B(C6F5)3), an activating agent capable of cyclization but not dealkylation, resulted in the isolation of a postcyclization zwitterionic intermediate. Kinetic studies via UV-vis spectroscopy with this boron reagent found second-order kinetics, supporting the likely relevancy of intermediates in this system to the ClBcat system. Computational studies comparing ClBcat with BCl3 as an activating agent showed why BCl3, in contrast to ClBcat, failed to mediate the complete the cyclization/demethylation reaction sequence by itself. Overall, the results support a mechanism in which the ClBcat reagent serves a bifunctional role by sequentially activating the alkyne, despite being less electrophilic than other known alkyne-activating reagents and then providing chloride for post-rate-determining demethylation/neutralization of the resulting zwitterionic intermediate.
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Affiliation(s)
- Adena Issaian
- Department of Chemistry, University of California , Irvine, California 92617-2025, United States
| | - Darius J Faizi
- Department of Chemistry, University of California , Irvine, California 92617-2025, United States
| | - Johnathan O Bailey
- Department of Chemistry, Texas A&M University , P.O. Box 30012, College Station, Texas 77842, United States
| | - Peter Mayer
- Department of Chemistry, Ludwig Maximilian University of Munich , Munich, 80539, Germany
| | - Guillaume Berionni
- Department of Chemistry, Ludwig Maximilian University of Munich , Munich, 80539, Germany
| | - Daniel A Singleton
- Department of Chemistry, Texas A&M University , P.O. Box 30012, College Station, Texas 77842, United States
| | - Suzanne A Blum
- Department of Chemistry, University of California , Irvine, California 92617-2025, United States
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23
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Fasano V, Curless LD, Radcliffe JE, Ingleson MJ. Frustrated Lewis Pair Mediated 1,2-Hydrocarbation of Alkynes. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201705100] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Affiliation(s)
- Valerio Fasano
- School of Chemistry; University of Manchester; Oxford Road Manchester M13 9PL UK
| | - Liam D. Curless
- School of Chemistry; University of Manchester; Oxford Road Manchester M13 9PL UK
| | - James E. Radcliffe
- School of Chemistry; University of Manchester; Oxford Road Manchester M13 9PL UK
| | - Michael J. Ingleson
- School of Chemistry; University of Manchester; Oxford Road Manchester M13 9PL UK
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