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Alonso M, Bettens T, Eeckhoudt J, Geerlings P, De Proft F. Wandering through quantum-mechanochemistry: from concepts to reactivity and switches. Phys Chem Chem Phys 2023; 26:21-35. [PMID: 38086672 DOI: 10.1039/d3cp04907h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
Mechanochemistry has experienced a renaissance in recent years witnessing, at the molecular level, a remarkable interplay between theory and experiment. Molecular mechanochemistry has welcomed a broad spectrum of quantum-chemical methods to evaluate the influence of an external mechanical force on molecular properties. In this contribution, an overview is given on recent work on quantum mechanochemistry in the Brussels Quantum Chemistry group (ALGC). The effect of an external force was scrutinized both in fundamental topics, like reactivity descriptors in Conceptual DFT, and in applied topics, such as designing molecular force probes and tuning the stereoselectivity of certain types of reactions. In the conceptual part, a brief overview of the techniques introducing mechanical forces into a quantum-mechanical description of a molecule is followed by an introduction to conceptual DFT. The evolution of the electronic chemical potential (or electronegativity), chemical hardness and electrophilicity are investigated when a chemical bond in a series of diatomics is put under mechanical stress. Its counterpart, the influence of mechanical stress on bond angles, is analyzed by varying the strain present in alkyne triple bonds by applying a bending force, taking the strain promoted alkyne-azide coupling cycloaddition as an example. The increase of reactivity of the alkyne upon bending is probed by Fukui functions and the local softness. In the applied part, a new molecular force probe is presented based on an intramolecular 6π-electrocyclization in constrained polyenes operating under thermal conditions. A cyclic process is conceived where ring opening and closure are triggered by applying or removing an external pulling force. The efficiency of mechanical activation strongly depends on the magnitude of the applied force and the distance between the pulling points. The idea of pulling point distances as a tool to identify new mechanochemical processes is then tested in [28]hexaphyrins with an intricate equilibrium between Möbius aromatic and Hückel antiaromatic topologies. A mechanical force is shown to trigger the interconversion between the two topologies, using the distance matrix as a guide to select appropriate pulling points. In a final application, the Felkin-Anh model for the addition of nucleophiles to chiral carbonyls under the presence of an external mechanical force is scrutinized. By applying a force for restricting the conformational freedom of the chiral ketone, otherwise inaccessible reaction pathways are promoted on the force-modified potential energy surfaces resulting in a diastereoselectivity different from the force-free reaction.
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Affiliation(s)
- Mercedes Alonso
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium.
| | - Tom Bettens
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium.
| | - Jochen Eeckhoudt
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium.
| | - Paul Geerlings
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium.
| | - Frank De Proft
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050 Brussels, Belgium.
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Bettens T, Alonso M, Geerlings P, De Proft F. Mechanochemical Felkin-Anh Model: Achieving Forbidden Reaction Outcomes with Mechanical Force. J Org Chem 2023; 88:2046-2056. [PMID: 36735279 DOI: 10.1021/acs.joc.2c02318] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Anti-Felkin-Anh diastereoselectivity can be achieved for nucleophilic additions to α-chiral ketones upon stretching the ketone with a mechanical pulling force. Herein, a mechanochemical Felkin-Anh model is proposed for predicting the outcome of a nucleophilic addition to an α-chiral ketone. Essentially, the fully stretched chiral ketone has one substituent shielding each side of the carbonyl, in contrast to the Felkin-Anh model, in which free rotation around a bond is required to achieve the two rotamers of the ketone. Depending on the pulling scenario, either Felkin-Anh or anti-Felkin-Anh diastereoselectivity is obtained. The model is entirely based on the distance between the pulling points, which is maximized in the anti-periplanar arrangement. The major diastereomer is associated with the approach with the least steric interactions. The intuitive model is validated by means of mechanochemical density functional theory calculations. Importantly, the ketone is fully stretched in the sub 1 nN force regime, thus minimizing the risk of undesired homolytic bond rupture. Moreover, the mechanical force is not used for lowering the reaction barriers associated with the nucleophilic addition; instead, it is solely applied for locking the conformation of a molecule and provoking otherwise inaccessible reaction pathways on the force-modified potential energy surface.
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Affiliation(s)
- Tom Bettens
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050Brussels, Belgium
| | - Mercedes Alonso
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050Brussels, Belgium
| | - Paul Geerlings
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050Brussels, Belgium
| | - Frank De Proft
- Eenheid Algemene Chemie (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, 1050Brussels, Belgium
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Tanpure SD, Kardile RD, Liu RS. Relay Zn( ii)- and Au( i)-catalyzed aziridination/cyclization/ring expansion sequence to form 3-benzazepine derivatives. Org Chem Front 2023. [DOI: 10.1039/d3qo00134b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/03/2023]
Abstract
The synthesis of 3H-benzo[d]azepine-2-carboxylates from 2-alkynylphenyl aldimines and α-diazo esters using Zn(ii) and Au(i) catalysts is described.
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Verhoeven J, Deraet X, Pande V, Sun W, Alonso M, De Proft F, Meerpoel L, Thuring JW, Verniest G. Synthesis and Reactivity of Spirocarbocycles as Scaffolds for Nucleoside Analogues. J Org Chem 2020; 85:14989-15005. [PMID: 33196210 DOI: 10.1021/acs.joc.0c01825] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
A novel class of substituted spiro[3.4]octanes can be accessed via a [2 + 2]-cycloaddition of dichloroketene on a readily prepared exo-methylene cyclopentane building block. This reaction sequence was found to be robust on a multigram scale and afforded a central spirocyclobutanone scaffold for carbocyclic nucleosides. The reactivity of this constrained building block was evaluated and compared to the corresponding 4'-spirocyclic furanose analogues. Density functional theory calculations were performed to support the observed selectivity in the carbonyl reduction of spirocyclobutanone building blocks. Starting from novel spirocyclic intermediates, we exemplified the preparation of an undescribed class of carbocyclic nucleoside analogues and provided a proof of concept for application as inhibitors for the protein methyltransferase target PRMT5.
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Affiliation(s)
- Jonas Verhoeven
- Research Group of Organic Chemistry (ORGC), Department of Chemistry and Department of Bio-Engineering Sciences, Faculty of Science and Bio-Engineering Sciences, Vrije Universiteit Brussel (VUB) Pleinlaan 2, 1050 Brussels, Belgium.,Janssen Pharmaceutica NV Turnhoutseweg 30, 2340 Beerse, Belgium
| | - Xavier Deraet
- Research Group of General Chemistry (ALGC), Vrije Universiteit Brussel (VUB), 1050 Brussels, Belgium
| | - Vineet Pande
- Janssen Pharmaceutica NV Turnhoutseweg 30, 2340 Beerse, Belgium
| | - Weimei Sun
- Janssen Pharmaceutica NV Turnhoutseweg 30, 2340 Beerse, Belgium
| | - Mercedes Alonso
- Research Group of General Chemistry (ALGC), Vrije Universiteit Brussel (VUB), 1050 Brussels, Belgium
| | - Frank De Proft
- Research Group of General Chemistry (ALGC), Vrije Universiteit Brussel (VUB), 1050 Brussels, Belgium
| | - Lieven Meerpoel
- Janssen Pharmaceutica NV Turnhoutseweg 30, 2340 Beerse, Belgium
| | | | - Guido Verniest
- Research Group of Organic Chemistry (ORGC), Department of Chemistry and Department of Bio-Engineering Sciences, Faculty of Science and Bio-Engineering Sciences, Vrije Universiteit Brussel (VUB) Pleinlaan 2, 1050 Brussels, Belgium.,Janssen Pharmaceutica NV Turnhoutseweg 30, 2340 Beerse, Belgium
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Deraet X, Voets L, Van Lommel R, Verniest G, De Proft F, De Borggraeve W, Alonso M. Stereoselective Reductions of 3-Substituted Cyclobutanones: A Comparison between Experiment and Theory. J Org Chem 2020; 85:7803-7816. [PMID: 32441520 DOI: 10.1021/acs.joc.0c00464] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The stereoselective reduction of carbonyls is of key importance in the total synthesis of natural products and in medicinal chemistry. Nevertheless, models for rationalizing the stereoselectivity of the hydride reductions of cyclobutanones toward cyclobutanols are largely lacking, unlike cyclohexanone reductions. In order to elucidate the factors that control the stereoselectivity of these reductions, we have investigated the effect of the reaction temperature, solvent, substituent, and type of reducing agent using a synergistic experimental-computational approach. On the experimental side, the hydride reduction of 3-substituted cyclobutanones was proven to be highly selective for the formation of cis alcohol (>90%), irrespective of the size of the hydride reagent. The pronounced selectivity can be further enhanced by lowering the reaction temperature or decreasing the solvent polarity. On the computational side, density functional theory and noncovalent interaction analysis reveal that torsional strain plays a major role in the preference for the antifacial hydride approach, consistent with the Felkin-Anh model. In the presence of the benzyloxy substituent, the high selectivity for the cis isomer is also driven by repulsive electrostatic interactions in the case of a syn-facial hydride attack. The computed cis/trans ratios are in good agreement with the experimental ones and thus show the potential of computational chemistry for predicting and rationalizing the stereoselectivity of hydride reductions of cyclobutanones.
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Affiliation(s)
- Xavier Deraet
- Department of General Chemistry (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, Elsene, Brussels 1050, Belgium
| | - Lauren Voets
- Molecular Design and Synthesis, Department of Chemistry, KU Leuven, Celestijnenlaan 200F Leuven Chem&Tech, Box 2404, Leuven 3001, Belgium
| | - Ruben Van Lommel
- Department of General Chemistry (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, Elsene, Brussels 1050, Belgium.,Molecular Design and Synthesis, Department of Chemistry, KU Leuven, Celestijnenlaan 200F Leuven Chem&Tech, Box 2404, Leuven 3001, Belgium
| | - Guido Verniest
- Research Group of Organic Chemistry (ORGC), Departments of Bio-engineering Sciences and Chemistry, Vrije Universiteit Brussel (VUB), Pleinlaan 2, Elsene, Brussels 1050, Belgium
| | - Frank De Proft
- Department of General Chemistry (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, Elsene, Brussels 1050, Belgium
| | - Wim De Borggraeve
- Molecular Design and Synthesis, Department of Chemistry, KU Leuven, Celestijnenlaan 200F Leuven Chem&Tech, Box 2404, Leuven 3001, Belgium
| | - Mercedes Alonso
- Department of General Chemistry (ALGC), Vrije Universiteit Brussel (VUB), Pleinlaan 2, Elsene, Brussels 1050, Belgium
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