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Inoue T, Morita N, Amijima Y, Sakai R, Hamada S, Nakamura S, Kobayashi Y, Furuta T. Formation of chalcogen-bonding interactions and their role in the trans- trans conformation of thiourea. Org Biomol Chem 2024; 22:5301-5305. [PMID: 38898797 DOI: 10.1039/d4ob00723a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/21/2024]
Abstract
The chalcogen-bonding interactions formed at both sides of the thiocarbonyl group in thiourea were investigated. In particular, the role of these chalcogen-bonding interactions in the trans-trans conformation of thiourea was evaluated via single-crystal X-ray diffraction analysis and DFT calculations. The obtained results indicate that the Se⋯S⋯Se dual chalcogen-bonding interactions play a stronger role in controlling the planar structure than the S⋯S⋯S interactions.
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Affiliation(s)
- Takumi Inoue
- Laboratory of Pharmaceutical Chemistry, Kyoto Pharmaceutical University, Yamashina-ku, Kyoto 607-8414, Japan.
| | - Nami Morita
- Laboratory of Pharmaceutical Chemistry, Kyoto Pharmaceutical University, Yamashina-ku, Kyoto 607-8414, Japan.
| | - Yui Amijima
- Laboratory of Pharmaceutical Chemistry, Kyoto Pharmaceutical University, Yamashina-ku, Kyoto 607-8414, Japan.
| | - Rika Sakai
- Laboratory of Pharmaceutical Chemistry, Kyoto Pharmaceutical University, Yamashina-ku, Kyoto 607-8414, Japan.
| | - Shohei Hamada
- Laboratory of Pharmaceutical Chemistry, Kyoto Pharmaceutical University, Yamashina-ku, Kyoto 607-8414, Japan.
| | - Seikou Nakamura
- Laboratory of Pharmacognosy, Kyoto Pharmaceutical University, Yamashina-ku, Kyoto 607-8414, Japan
| | - Yusuke Kobayashi
- Laboratory of Pharmaceutical Chemistry, Kyoto Pharmaceutical University, Yamashina-ku, Kyoto 607-8414, Japan.
| | - Takumi Furuta
- Laboratory of Pharmaceutical Chemistry, Kyoto Pharmaceutical University, Yamashina-ku, Kyoto 607-8414, Japan.
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2
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Rummel L, Schreiner PR. Advances and Prospects in Understanding London Dispersion Interactions in Molecular Chemistry. Angew Chem Int Ed Engl 2024; 63:e202316364. [PMID: 38051426 DOI: 10.1002/anie.202316364] [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: 10/29/2023] [Revised: 12/03/2023] [Accepted: 12/05/2023] [Indexed: 12/07/2023]
Abstract
London dispersion (LD) interactions are the main contribution of the attractive part of the van der Waals potential. Even though LD effects are the driving force for molecular aggregation and recognition, the role of these omnipresent interactions in structure and reactivity had been largely underappreciated over decades. However, in the recent years considerable efforts have been made to thoroughly study LD interactions and their potential as a chemical design element for structures and catalysis. This was made possible through a fruitful interplay of theory and experiment. This review highlights recent results and advances in utilizing LD interactions as a structural motif to understand and utilize intra- and intermolecularly LD-stabilized systems. Additionally, we focus on the quantification of LD interactions and their fundamental role in chemical reactions.
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Affiliation(s)
- Lars Rummel
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392, Giessen, Germany
| | - Peter R Schreiner
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392, Giessen, Germany
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3
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Blechschmidt DR, Mergendahl C, Kass SR. Metallocenium incorporated charge-enhanced thiourea catalysts. Org Biomol Chem 2024; 22:1788-1793. [PMID: 38343361 DOI: 10.1039/d3ob02007j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/29/2024]
Abstract
Several metallocenium derivatives were prepared including N-ferrocenium-N'-phenylthiourea tetrakis-[3,5-bis(trifluoromethyl)phenyl]borate (BArF4, 4a), N-methylferrocenium-N'-phenylthiourea BArF4 (4b) and N-cobaltocenium-N'-phenylthiourea BArF4 (5). These compounds are competent catalysts for the Friedel-Crafts alkylation of indoles with trans-β-nitrostyrenes, and are much more active than their reduced non-charged forms. The iron derivatives are less stable than the cobalt analog and were generated and used in situ whereas the cobalt-containing thiourea was isolated and characterized by X-ray crystallography. All three of these metallocenium salts have Lewis and Brønsted acidic sites which were exploited in tandem to afford charge-activated catalysts.
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Affiliation(s)
- Daniel R Blechschmidt
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455, USA.
| | - Cal Mergendahl
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455, USA.
| | - Steven R Kass
- Department of Chemistry, University of Minnesota, 207 Pleasant Street SE, Minneapolis, MN 55455, USA.
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4
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Burra VLSP, Sahoo PS, Dhankhar A, Jhajj J, Kasamuthu PS, K SSVK, Macha SKR. Understanding the structural basis of the binding specificity of c-di-AMP to M. smegmatis RecA using computational biology approach. J Biomol Struct Dyn 2024; 42:2043-2057. [PMID: 38093709 DOI: 10.1080/07391102.2023.2227709] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2022] [Accepted: 04/09/2023] [Indexed: 02/21/2024]
Abstract
Mycobacterium tuberculosis RecA (MtRecA), a protein involved in DNA repair, homologous recombination and SOS pathway, contributes to the development of multidrug resistance. ATP binding-site in RecA has been a drug target to disable RecA dependent DNA repair. For the first time, experiments have shown the existence and binding of c-di-AMP to a novel allosteric site in the C-terminal-Domain (CTD) of Mycobacterium smegmatis RecA (MsRecA), a close homolog of MtRecA. In addition, it was observed that the c-di-AMP was not binding to Escherichia coli RecA (EcRecA). This article analyses the possible interactions of the three RecA homologs with the various c-di-AMP conformations to gain insights into the structural basis of the natural preference of c-di-AMP to MsRecA and not to EcRecA, using the structural biology tools. The comparative analysis, based on amino acid composition, homology, motifs, residue types, docking, molecular dynamics simulations and binding free energy calculations, indeed, conclusively indicates strong binding of c-di-AMP to MsRecA. Having very similar results as MsRecA, it is highly plausible for c-di-AMP to strongly bind MtRecA as well. These insights from the in-silico studies adds a new therapeutic approach against TB through design and development of novel allosteric inhibitors for the first time against MtRecA.Communicated by Ramaswamy H. Sarma.
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Affiliation(s)
- V L S Prasad Burra
- Centre for Advanced Research and Innovation in Structural Biology of Diseases, K L E F (Deemed to be) University, Vaddeswaram, Andhra Pradesh, India
| | - Partha Sarathi Sahoo
- Centre for Advanced Research and Innovation in Structural Biology of Diseases, K L E F (Deemed to be) University, Vaddeswaram, Andhra Pradesh, India
| | - Amit Dhankhar
- Centre for Advanced Research and Innovation in Structural Biology of Diseases, K L E F (Deemed to be) University, Vaddeswaram, Andhra Pradesh, India
| | - Jatinder Jhajj
- Centre for Advanced Research and Innovation in Structural Biology of Diseases, K L E F (Deemed to be) University, Vaddeswaram, Andhra Pradesh, India
| | - Prasanna Sudharson Kasamuthu
- Centre for Advanced Research and Innovation in Structural Biology of Diseases, K L E F (Deemed to be) University, Vaddeswaram, Andhra Pradesh, India
| | - S S V Kiran K
- Centre for Advanced Research and Innovation in Structural Biology of Diseases, K L E F (Deemed to be) University, Vaddeswaram, Andhra Pradesh, India
| | - Samuel Krupa Rakshan Macha
- Centre for Advanced Research and Innovation in Structural Biology of Diseases, K L E F (Deemed to be) University, Vaddeswaram, Andhra Pradesh, India
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5
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Averdunk C, Hanke K, Schatz D, Wegner HA. Molecular Wind-Up Meter for the Quantification of London Dispersion Interactions. Acc Chem Res 2024; 57:257-266. [PMID: 38131644 DOI: 10.1021/acs.accounts.3c00616] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
ConspectusThe experimental quantification of interactions on the molecular level provides the necessary basis for the design of functional materials and chemical processes. The interplay of multiple parameters and the small quantity of individual interactions pose a special challenge for such endeavors. The common method is the use of molecular balances, which can exist in two different states. Thereby, a stabilizing interaction can occur in one of the states, favoring its formation and thus affecting the thermodynamic equilibrium of the system. One challenge is determining the change in this equilibrium since various analytical methods could not be applied to fast-changing equilibria. A new and promising method for quantifying molecular interactions is the use of Molecular Wind-up Meters (MWM) in which the change in kinetics, rather than the effect on thermodynamics, is investigated. An MWM is transformed with an energy input (e.g. irradiation) into a metastable state. Then, the rate of thermal transformation back to the ground state is measured. The strength of interactions present in the metastable state controls the kinetics of the back reactions, allowing direct correlation. The advantage of this approach lies in the high sensitivity (energy differences can be larger by 1 order of magnitude) and, in general, allows the use of a broader range of solvents and analytical methods. An Azobenzene-based MWM has been established as a powerful tool to quantify London dispersion interactions. London dispersion (LD) represents the attractive part of the van der Waals potential. Although neglected in the past due to its weak character, it has been shown that the influence of LD on the structure, stability, and reactivity of matter can be decisive. Especially in larger molecules, its energy contribution increases overproportionately with the number of atoms, which has sparked increasing interest in the use of so-called dispersion energy donors (DED) as a new structural element. Application of the azobenzene-based MWM not only allowed the differentiation of bulkiness, but also systematically addressed the influence of the length of n-alkyl chains. Additionally, the solvent influence on LD was studied. Based on the azobenzene MWM, an increment system has been proposed, allowing a rough estimate of the effect of a specific DED.
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Affiliation(s)
- Conrad Averdunk
- Institute of Organic Chemistry, Justus Liebig University Giessen, Heinrich-Buff-Ring 17, 35392 Giessen, Germany
- Center of Materials Research (LaMa), Justus Liebig University Giessen, Heinrich-Buff-Ring 16, 35392 Giessen, Germany
| | - Kai Hanke
- Institute of Organic Chemistry, Justus Liebig University Giessen, Heinrich-Buff-Ring 17, 35392 Giessen, Germany
- Center of Materials Research (LaMa), Justus Liebig University Giessen, Heinrich-Buff-Ring 16, 35392 Giessen, Germany
| | - Dominic Schatz
- Institute of Organic Chemistry, Justus Liebig University Giessen, Heinrich-Buff-Ring 17, 35392 Giessen, Germany
- Center of Materials Research (LaMa), Justus Liebig University Giessen, Heinrich-Buff-Ring 16, 35392 Giessen, Germany
| | - Hermann A Wegner
- Institute of Organic Chemistry, Justus Liebig University Giessen, Heinrich-Buff-Ring 17, 35392 Giessen, Germany
- Center of Materials Research (LaMa), Justus Liebig University Giessen, Heinrich-Buff-Ring 16, 35392 Giessen, Germany
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6
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Gravillier LA, Cockroft SL. Context-Dependent Significance of London Dispersion. Acc Chem Res 2023; 56:3535-3544. [PMID: 37994023 DOI: 10.1021/acs.accounts.3c00625] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2023]
Abstract
ConspectusLondon forces constitute an attractive component of van der Waals interactions and originate from transient correlated momentary dipoles in adjacent atoms. The in-depth investigation of London dispersion forces poses notable challenges, especially in solution, owing to their inherently weak and competing character. Our objective in this Account is to shed light on the context-dependent significance of London dispersion forces by contrasting our own experimental findings with those from other research endeavors. Specifically, we will explore how factors such as the choice of system and solvent can influence the apparent role of London dispersion forces in molecular recognition processes. We initiate our Account by scrutinizing the Wilcox balance, which has yielded diverse and occasionally contradictory results. Following that, we provide an overview of the role of London dispersion forces and their context-dependent variations, encompassing alkyl-alkyl, halogen-π, alkyl-π, and aromatic stacking interactions.Several experimental investigations have revealed how difficult it is to measure the significance of London dispersion in solution. Indeed, dispersion forces seldom act as the exclusive driving force in molecular recognition processes, and solvation energetics also strongly influence equilibria and kinetics. Molecular balances that bring apolar functional groups into contact have proven to be instrumental in the experimental measurement of dispersion. The intramolecular approach avoids the need to pay the entropic cost of bringing interacting groups into contact, while also enabling solvent screening. Such experimental studies have found dispersion interactions between functional groups to be very weak (<5 kJ mol-1), meaning that they frequently take backstage to electrostatic contributions and solvophobic effects and are readily damped by competitive dispersion interactions with the solvent. By using such approaches, competitive dispersion interactions with the solvent have been shown to be described by the bulk polarizability of the solvent (perfluoroalkanes have the lowest bulk polarizabilities, while carbon disulfide has one of the highest). Dispersion interactions are also strongly distance-dependent, which results in considerable context-dependent outcomes across different investigations. For example, we caution against the risk of attributing the stability of a "more sterically hindered" isomer as arising from intramolecular dispersion forces. The total energy of the system can reveal other contributions to stability, such as nonintuitive minimization of strain elsewhere in the molecule. Indeed, the delicate distance-dependent balance between sterics and London dispersion means that even subtle changes in size and geometry can lead to disparate behavior. Similarly, solvophobic effects also contribute to stabilizing contacts between bulky functional groups, which can be revealed if there is a correlation with the cohesive energy density of the solvent.
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Affiliation(s)
- Louis-Albin Gravillier
- EaStCHEM School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh EH9 3FJ, U.K
| | - Scott L Cockroft
- EaStCHEM School of Chemistry, University of Edinburgh, Joseph Black Building, David Brewster Road, Edinburgh EH9 3FJ, U.K
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7
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Gramüller J, Gschwind RM. An NMR Spectroscopy View on London Dispersion in Catalysis: Detection, Quantification, and Application in Ion Pair and Transition Metal Catalysis. Acc Chem Res 2023; 56:2968-2979. [PMID: 37889132 DOI: 10.1021/acs.accounts.3c00431] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2023]
Abstract
ConspectusThe energetic contribution of London dispersion (LD) can cover a broad range from very few to hundreds of kJ mol-1 for extended interaction interfaces due to its pairwise additivity. However, for a designed and successful application of LD in chemical catalysis, there are still many obstacles and questions that remain. In principle, LD can be regarded as the attractive part of the van der Waals potential. Thus, considering the whole van der Waals potential, including the repulsive part (steric repulsion), the ideal solution to the problem in catalysis would be to design compatible interaction interfaces at exactly the correct distance. In the case of a self-assembled, flexible structure arrangement, entropic contributions and solvent interactions might be detrimental. In the case of a rigid catalyst pocket, steric hindrance might not allow for large substituents that are usually applied as dispersion energy donors (DEDs). For a working catalytic system, the following question arises: how is it possible to dissect the complex interaction interfaces in terms of energetic contributions? Usually, the energetic contribution of LD to catalysis is addressed by using calculations. However, adequately computing the correct energetic contributions can be extremely challenging for a vast conformational space with all kinds of intermolecular interactions. Thus, experimental data are essential for comparison or benchmarking.Therefore, in this Account, we describe our quest for detailed experimental data obtained via NMR spectroscopy to experimentally dissect and quantify LD in catalytic systems. In addition, we address the question of whether bulky substituents used as DEDs can be used in confined catalytic pockets. With the example of Pd phosphoramidite complexes, we show how it is possible to experimentally dissect and quantify the contribution of individual interaction areas in complicated transition metal complexes. Furthermore, a correlation between conformational rigidity and heterodimer preference clearly reveals that LD can only unfold its full potential in cases where entropic contributions are minimized. This finding can also explain the small contribution of LD in flexible and solvent-exposed molecular balances. In the field of Brønsted acid catalysis, we demonstrated that LD has a strong influence on the structures, stability, and populations of confined catalytic intermediates. LD is key for populating higher aggregates such as dimers. In addition, offsets between the experimental and computational results were observed and attributed to solvent-solute dispersion interactions. We studied the delicate interplay of attractive and repulsive interactions by adding bulky DED substituents onto a substrate, which can function as a molecular balance system. Intriguingly, the effect of LD on the free substrate was straightforwardly transferred onto the highly confined intermediates. Furthermore, this effect could even be read out in the enantioselectivities of the underlying reaction. This conceptualized a general approach regarding how LD can be used beneficially in catalysis to convert from moderate/good to excellent stereoselectivities. It showcased that bulky groups such as tert-butyl must not only be regarded as occupied volumes.
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Affiliation(s)
- Johannes Gramüller
- Institute of Organic Chemistry, University of Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany
| | - Ruth M Gschwind
- Institute of Organic Chemistry, University of Regensburg, Universitätsstraße 31, D-93053 Regensburg, Germany
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8
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Mears KL, Power PP. London Dispersion Effects on the Stability of Heavy Tetrel Molecules. Chemistry 2023; 29:e202301247. [PMID: 37263972 DOI: 10.1002/chem.202301247] [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: 04/19/2023] [Revised: 05/28/2023] [Accepted: 05/31/2023] [Indexed: 06/03/2023]
Abstract
London dispersion (LD) interactions, which stem from long-range electron correlations arising from instantaneously induced dipoles can occur between neighboring atoms or molecules, for example, between H atoms within ligand C-H groups. These interactions are currently of interest as a new method of stabilizing long bonds and species with unusual oxidation states. They can also limit reactivity by installing LD enhanced groups into organic frameworks or ligand substituents. Here, we address the most recent advances in the design of LD enhanced ligands, the sterically counterintuitive structures that can be generated and the consequences that these interactions can have on the structures and reactivity of sterically crowded heavy group 14 species.
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Affiliation(s)
- Kristian L Mears
- Department of Chemistry, University of California One Shields Avenue, Davis, California, 95616, USA
| | - Philip P Power
- Department of Chemistry, University of California One Shields Avenue, Davis, California, 95616, USA
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9
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Schümann JM, Ochmann L, Becker J, Altun A, Harden I, Bistoni G, Schreiner PR. Exploring the Limits of Intramolecular London Dispersion Stabilization with Bulky Dispersion Energy Donors in Alkane Solution. J Am Chem Soc 2023; 145:2093-2097. [PMID: 36688409 DOI: 10.1021/jacs.2c13301] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
We present an experimental study of a cyclooctatetraene-based molecular balance disubstituted with increasingly bulky tert-butyl (tBu), adamantyl (Ad), and diamantyl (Dia) substituents in the 1,4-/1,6-positions for which we determined the valence-bond shift equilibrium in n-hexane (hex), n-octane (oct), and n-dodecane (dod). Computations including implicit and explicit solvation support our temperature-dependent NMR equilibrium measurements indicating that the more sterically crowded 1,6-isomer is always favored, irrespective of solvent, and that the free energy is quite insensitive to substituent size.
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Affiliation(s)
- Jan M Schümann
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany
| | - Lukas Ochmann
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany
| | - Jonathan Becker
- Institute of Analytical and Inorganic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany
| | - Ahmet Altun
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
| | - Ingolf Harden
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany
| | - Giovanni Bistoni
- Max-Planck-Institut für Kohlenforschung, Kaiser-Wilhelm-Platz 1, 45470 Mülheim an der Ruhr, Germany.,Dipartmento di Chimica, Biologia e Biotechnologie, Università Degli Studi Di Perugia, Via Elce di sotto, 8, 06123 Perugia, Italy
| | - Peter R Schreiner
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany
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10
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Abe R, Nagashima Y, Tanaka J, Tanaka K. Room Temperature Fluoranthene Synthesis through Cationic Rh(I)/H 8-BINAP-Catalyzed [2 + 2 + 2] Cycloaddition: Unexpected Acceleration due to Noncovalent Interactions. ACS Catal 2023. [DOI: 10.1021/acscatal.2c05683] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Affiliation(s)
- Ryota Abe
- Department of Chemical Science and Engineering, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8550, Japan
| | - Yuki Nagashima
- Department of Chemical Science and Engineering, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8550, Japan
| | - Jin Tanaka
- Department of Chemical Science and Engineering, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8550, Japan
| | - Ken Tanaka
- Department of Chemical Science and Engineering, Tokyo Institute of Technology, Ookayama, Meguro-ku, Tokyo 152-8550, Japan
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11
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Gramüller J, Franta M, Gschwind RM. Tilting the Balance: London Dispersion Systematically Enhances Enantioselectivities in Brønsted Acid Catalyzed Transfer Hydrogenation of Imines. J Am Chem Soc 2022; 144:19861-19871. [PMID: 36260790 DOI: 10.1021/jacs.2c07563] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
London dispersion (LD) is attracting more and more attention in catalysis since LD is ubiquitously present and cumulative. Since dispersion is hard to grasp, recent research has concentrated mainly on the effect of LD in individual catalytic complexes or on the impact of dispersion energy donors (DEDs) on balance systems. The systematic transfer of LD effects onto confined and more complex systems in catalysis is still in its infancy, and no general approach for using DED residues in catalysis has emerged so far. Thus, on the example of asymmetric Brønsted acid catalyzed transfer hydrogenation of imines, we translated the findings of previously isolated balance systems onto confined catalytic intermediates, resulting in a systematic enhancement of stereoselectivity when employing DED-substituted substrates. As the imine substrate is present as Z- and E-isomers, which can, respectively, be converted to R- and S-product enantiomers, implementing tert-butyl groups as DED residues led to an additional stabilization of the Z-imine by up to 4.5 kJ/mol. NMR studies revealed that this effect is transferred onto catalyst/imine and catalyst/imine/nucleophile intermediates and that the underlying reaction mechanism is not affected. A clear correlation between ee and LD stabilization was demonstrated for 3 substrates and 10 catalysts, allowing to convert moderate-good to good-excellent enantioselectivities. Our findings conceptualize a general approach on how to beneficially employ DED residues in catalysis: they clearly showcase that bulky alkyl residues such as tert-butyl groups must be considered regarding not only their repulsive steric bulk but also their attractive properties even in catalytic complexes.
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Affiliation(s)
- Johannes Gramüller
- Institute of Organic Chemistry, University of Regensburg, 93040 Regensburg, Germany
| | - Maximilian Franta
- Institute of Organic Chemistry, University of Regensburg, 93040 Regensburg, Germany
| | - Ruth M Gschwind
- Institute of Organic Chemistry, University of Regensburg, 93040 Regensburg, Germany
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12
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Ehrhard AA, Gunkel L, Jäger S, Sell AC, Nagata Y, Hunger J. Elucidating Conformation and Hydrogen-Bonding Motifs of Reactive Thiourea Intermediates. ACS Catal 2022; 12:12689-12700. [PMID: 36313523 PMCID: PMC9594049 DOI: 10.1021/acscatal.2c03382] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 09/19/2022] [Indexed: 11/29/2022]
Abstract
![]()
Substituted diphenylthioureas (DPTUs) are efficient hydrogen-bonding
organo-catalysts, and substitution of DPTUs has been shown to greatly
affect catalytic activity. Yet, both the conformation of DPTUs in
solution and the conformation and hydrogen-bonded motifs within catalytically
active intermediates, pertinent to their mode of activation, have
remained elusive. By combining linear and ultrafast vibrational spectroscopy
with spectroscopic simulations and calculations, we show that different
conformational states of thioureas give rise to distinctively different
N–H stretching bands in the infrared spectra. In the absence
of hydrogen-bond-accepting substrates, we show that vibrational structure
and dynamics are highly sensitive to the substitution of DPTUs with
CF3 groups and to the interaction with the solvent environment,
allowing for disentangling the different conformational states. In
contrast to bare diphenylthiourea (0CF-DPTU), we find the catalytically
superior CF3-substituted DPTU (4CF-DPTU) to favor the trans–trans conformation in solution,
allowing for donating two hydrogen bonds to the reactive substrate.
In the presence of a prototypical substrate, DPTUs in trans–trans conformation hydrogen bond to the
substrate’s C=O group, as evidenced by a red-shift of
the N–H vibration. Yet, our time-resolved infrared experiments
indicate that only one N–H group forms a strong hydrogen bond
to the carbonyl moiety, while thiourea’s second N–H
group only weakly interacts with the substrate. Our data indicate
that hydrogen-bond exchange between these N–H groups occurs
on the timescale of a few picoseconds for 0CF-DPTU and is significantly
accelerated upon CF3 substitution. Our results highlight
the subtle interplay between conformational equilibria, bonding states,
and bonding lifetimes in reactive intermediates in thiourea catalysis,
which help rationalize their catalytic activity.
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Affiliation(s)
- Amelie A. Ehrhard
- Max-Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Lucas Gunkel
- Max-Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Sebastian Jäger
- Max-Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Arne C. Sell
- Max-Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Yuki Nagata
- Max-Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
| | - Johannes Hunger
- Max-Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany
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13
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Ochmann L, Fuhrmann M, Gössl FJ, Makaveev A, Schreiner PR. All That metas─Synthesis of Dispersion Energy Donor-Substituted Benzenes. Org Lett 2022; 24:6968-6972. [DOI: 10.1021/acs.orglett.2c02780] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Lukas Ochmann
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany
| | - Michael Fuhrmann
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany
| | - Felix J. Gössl
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany
| | - Alexander Makaveev
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany
| | - Peter R. Schreiner
- Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany
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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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