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Schleif T, Prado Merini M, Henkel S, Sander W. Solvation Effects on Quantum Tunneling Reactions. Acc Chem Res 2022; 55:2180-2190. [PMID: 35730754 DOI: 10.1021/acs.accounts.2c00151] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
A decisive factor for obtaining high yields and selectivities in organic synthesis is the choice of the proper solvent. Solvent selection is often guided by the intuitive understanding of transition state-solvent interactions. However, quantum-mechanical tunneling can significantly contribute to chemical reactions, circumventing the transition state and thus depriving chemists of their intuitive handle on the reaction kinetics. In this Account, we aim to provide rationales for the effects of solvation on tunneling reactions derived from experiments performed in cryogenic matrices.The tunneling reactions analyzed here cover a broad range of prototypical organic transformations that are subject to strong solvation effects. Examples are the hydrogen tunneling probability for the cis-trans isomerization of formic acid which is strongly reduced upon formation of hydrogen-bonded complexes and the [1,2]H-shift in methylhydroxycarbene where a change in product selectivity is predicted upon interaction with hydrogen bond acceptors.Not only hydrogen but also heavy atom tunneling can exhibit strong solvent effects. The direction of the nearly degenerate valence tautomerization between benzene oxide and oxepin was found to reverse upon formation of a halogen or hydrogen bond with ICF3 or H2O. But even in the absence of strong noncovalent interactions such as hydrogen or halogen bonding, solvation can have a decisive effect on tunneling as evidenced by the Cope rearrangement of semibullvalenes via heavy-atom tunneling. Can quantum tunneling be catalyzed? The acceleration of the ring expansion of 1H-bicyclo[3.1.0.]-hexa-3,5-dien-2-one by complexation with Lewis acids provides a proof-of-concept for tunneling catalysis.Two concepts are central for the explanation and prediction of solvation effects on tunneling phenomena: a simple approach expands the Born-Oppenheimer approximation by separating nuclear degrees of freedom into intra- and intermolecular degrees. Intermolecular movements represent the slowest motions within molecular aggregates, thus effectively freezing the position of the solvent in relation to the reactant during the tunneling process. Another useful approach is to treat reactants and products by separate single-well potentials, where the intersection represents the transition state. Thus, stabilization of the reactants via solvation should result in an increase in barrier heights and widths which in turn lowers tunneling probabilities. These simple models can predict trends in tunneling kinetics and provide a rational basis for controlling tunneling reactions via solvation.
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Affiliation(s)
- Tim Schleif
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, 44801 Bochum, Germany
| | - Melania Prado Merini
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, 44801 Bochum, Germany
| | - Stefan Henkel
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, 44801 Bochum, Germany
| | - Wolfram Sander
- Lehrstuhl für Organische Chemie II, Ruhr-Universität Bochum, 44801 Bochum, Germany
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Roque JPL, Nunes CM, Fausto R. Matrix Isolation in Heterocyclic Chemistry. HETEROCYCLES 2022. [DOI: 10.1002/9783527832002.ch12] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Reva I, Jesus AJL, Nunes CM, Roque JPL, Fausto R. UV-Induced Photochemistry of 1,3-Benzoxazole, 2-Isocyanophenol, and 2-Cyanophenol Isolated in Low-Temperature Ar Matrixes. J Org Chem 2021; 86:6126-6137. [PMID: 33872502 DOI: 10.1021/acs.joc.0c02970] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The monomers of 1,3-benzoxazole isolated in a cryogenic argon matrix were characterized by infrared spectroscopy. The photochemistry of matrix-isolated 1,3-benzoxazole, induced by excitation with a frequency-tunable narrowband UV light, was investigated. Irradiation at 233 nm resulted in a nearly quantitative conversion of 1,3-benzoxazole into 2-isocyanophenol. The individual photochemical behavior of the in situ produced 2-isocyanophenol was studied upon excitations at 290 nm, where 1,3-benzoxazole does not react. The photochemistry of isomeric matrix-isolated 2-cyanophenol was also studied. The photoreactions of 2-substituted (cyano- or isocyano-) phenols were found to have many similarities: (i) OH bond cleavage, yielding a 2-substituted (cyano- or isocyano-) phenoxyl radical and an H-atom, (ii) recombination of the detached H-atom, resulting in an oxo tautomer, and (iii) decomposition leading to fulvenone, together with HCN and HNC. In another photoprocess, 2-cyanophenol undergoes a [1,5] H-shift from the hydroxyl group to the cyano group yielding isomeric ketenimine. The analogous [1,5] H-shift from the hydroxyl group to the isocyano group must have also occurred in 2-isocyanophenol; however, the resulting nitrile ylide isomer is kinetically unstable and collapses to benzoxazole. All photoproducts were characterized by comparing their observed infrared spectra with those computed at the B3LYP/6-311++G(d,p) level. The mechanistic analysis of the photochemistry occurring in the family of the title compounds is presented.
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Affiliation(s)
- Igor Reva
- University of Coimbra, CQC, Department of Chemistry, Coimbra 3004-535, Portugal.,University of Coimbra, CIEPQPF, Department of Chemical Engineering, Coimbra 3030-790, Portugal
| | - A J Lopes Jesus
- University of Coimbra, CQC, Faculty of Pharmacy, Coimbra 3004-295, Portugal
| | - Cláudio M Nunes
- University of Coimbra, CQC, Department of Chemistry, Coimbra 3004-535, Portugal
| | - José P L Roque
- University of Coimbra, CQC, Department of Chemistry, Coimbra 3004-535, Portugal
| | - Rui Fausto
- University of Coimbra, CQC, Department of Chemistry, Coimbra 3004-535, Portugal
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Lopes Jesus A, Reva I, Nunes CM, Roque JP, Pinto SM, Fausto R. Kinetically unstable 2–isocyanophenol isolated in cryogenic matrices: Vibrational excitation, conformational changes and spontaneous tunneling. Chem Phys Lett 2020. [DOI: 10.1016/j.cplett.2019.137069] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
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Lopes Jesus AJ, Nunes CM, Reva I, Pinto SMV, Fausto R. Effects of Entangled IR Radiation and Tunneling on the Conformational Interconversion of 2-Cyanophenol. J Phys Chem A 2019; 123:4396-4405. [DOI: 10.1021/acs.jpca.9b01382] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- A. J. Lopes Jesus
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
- CQC, Faculty of Pharmacy, University of Coimbra, 3004-295 Coimbra, Portugal
| | - Cláudio M. Nunes
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
| | - I. Reva
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
| | - Sandra M. V. Pinto
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
- Scuola Normale Superiore, Piazza dei Cavalieri, 7, I-56124 Pisa, Italy
| | - R. Fausto
- CQC, Department of Chemistry, University of Coimbra, 3004-535 Coimbra, Portugal
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Shimbayashi T, Sasakura K, Eguchi A, Okamoto K, Ohe K. Recent Progress on Cyclic Nitrenoid Precursors in Transition-Metal-Catalyzed Nitrene-Transfer Reactions. Chemistry 2018; 25:3156-3180. [PMID: 30183111 DOI: 10.1002/chem.201803716] [Citation(s) in RCA: 50] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2018] [Indexed: 12/20/2022]
Abstract
Nitrene-transfer reactions are powerful synthetic tools for the direct incorporation of nitrogen atoms into organic molecules. The discovery of novel nitrene-transfer reactions has been dominantly supported not only by improvements in transition-metal catalysts but also by the employment of novel precursors of nitrenoids. Since pioneering work involving the use of organic azides and iminoiodinanes as practical synthetic tools for nitrogen-containing compounds was reported, a new approach using various N-heterocycles containing strain energy or a weak bond has emerged. In this review, we briefly summarize the history of nitrene-transfer chemistry from the viewpoint of its precursors. In particular, the use of N-heterocycles such as 2H-azirines, 1,4,2-dioxazol-5-ones, 1,2,4-oxadiazol-5-ones, isoxazol-5(4H)-ones, and isoxazoles is comprehensively described, showing the recent remarkable progress in this chemistry.
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Affiliation(s)
- Takuya Shimbayashi
- Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto, 606-8501, Japan
| | - Kohei Sasakura
- Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto, 615-8510, Japan
| | - Akira Eguchi
- Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto, 615-8510, Japan
| | - Kazuhiro Okamoto
- Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto, 615-8510, Japan
| | - Kouichi Ohe
- Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto, 615-8510, Japan
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Nunes CM, Pinto SM, Reva I, Rosado MT, Fausto R. Photochemistry of matrix-isolated 3-chloro-1,2-benzisoxazole: Generation and characterization of 2-cyanophenoxyl radical and other reactive intermediates. J Mol Struct 2018. [DOI: 10.1016/j.molstruc.2017.11.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Pusch S, Tröster A, Lefrancois D, Farahani P, Dreuw A, Bach T, Opatz T. Mechanism and cis/trans Selectivity of Vinylogous Nazarov-type [6π] Photocyclizations. J Org Chem 2018; 83:964-972. [DOI: 10.1021/acs.joc.7b02982] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Stefan Pusch
- Institute
of Organic Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10−14, 55128 Mainz, Germany
| | - Andreas Tröster
- Department
Chemie and Catalysis Research Center (CRC), Technical University Munich, Lichtenbergstrasse 4, 85747 Garching, Germany
| | - Daniel Lefrancois
- Interdisciplinary
Center for Scientific Computing, Ruprecht-Karls University, Im Neuenheimer
Feld 205A, 69120 Heidelberg, Germany
| | - Pooria Farahani
- Instituto
de Química, Departamento de Química Fundamental, Universidade de São Paulo, C. P. 05508-000, São Paulo, SP Brazil
| | - Andreas Dreuw
- Interdisciplinary
Center for Scientific Computing, Ruprecht-Karls University, Im Neuenheimer
Feld 205A, 69120 Heidelberg, Germany
| | - Thorsten Bach
- Department
Chemie and Catalysis Research Center (CRC), Technical University Munich, Lichtenbergstrasse 4, 85747 Garching, Germany
| | - Till Opatz
- Institute
of Organic Chemistry, Johannes Gutenberg University Mainz, Duesbergweg 10−14, 55128 Mainz, Germany
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Nunes CM, Pinto SM, Reva I, Fausto R. Photochemistry of 3-amino-1,2-benzisoxazole: unexpected photoisomerization of an amino-spiro-2H-azirine to a 1H-diazirine. Tetrahedron Lett 2016. [DOI: 10.1016/j.tetlet.2016.09.098] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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