The Experts below are selected from a list of 2790 Experts worldwide ranked by ideXlab platform
Thijs Stuyver - One of the best experts on this subject based on the ideXlab platform.
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promotion energy analysis predicts reaction modes nucleophilic and Electrophilic Aromatic Substitution reactions
Journal of the American Chemical Society, 2021Co-Authors: Thijs Stuyver, Sason ShaikAbstract:To develop an approach to pre-emptively predict the existence of major reaction modes associated with a chemical system, based on exclusive consideration of reactant properties, we build herein on the valence bond perspective of chemical reactivity. In this perspective, elementary chemical reactions are conceptualized as crossovers between individual diabatic/semilocalized states. As demonstrated, the spacings between the main diabatic states in the reactant geometries-the so-called promotion energies-contain predictive information about which types of crossings are likely to occur on a potential energy surface, facilitating the identification of potential transition states and products. As an added bonus, promotion energy analysis provides direct insight into the impact of environmental effects, e.g., the presence of (polar) solvents and/or (local) electric fields, on a mechanistic landscape. We illustrate the usefulness of our approach by focusing on model nucleophilic and Electrophilic Aromatic Substitution reactions. Overall, we envision our analysis to be useful not only as a tool for conceptualizing individual mechanistic landscapes but also as a facilitator of systematic reaction-network exploration efforts. Because the emerging VB descriptors are computationally inexpensive (and can alternatively be inferred through machine learning), they could be evaluated on-the-fly as part of an exploration algorithm. The so-predicted reaction modes could subsequently be examined in detail through computationally more-demanding methods.
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Electrophilic Aromatic Substitution reactions mechanistic landscape electrostatic and electric field control of reaction rates and mechanistic crossovers
Journal of the American Chemical Society, 2019Co-Authors: Frank De Proft, Thijs Stuyver, David Danovich, Sason ShaikAbstract:This study investigates the rich mechanistic landscape of the iconic Electrophilic Aromatic Substitution (EAS) reaction class, in the gas phase, in solvents, and under stimulation by oriented external electric fields. The study uses DFT calculations, complemented by a qualitative valence bond (VB) perspective. We construct a comprehensive and unifying framework that elucidates the many surprising mechanistic features, uncovered in recent years, of this class of reactions. For example, one of the puzzling issues which have attracted significant interest recently is the finding of a variety of concerted mechanisms that do not involve the formation of σ-complex intermediates, in apparent contradiction to the generally accepted textbook mechanism. Our VB modeling elucidates the existence of both the concerted and stepwise mechanisms and uncovers the root causes and necessary conditions for the appearance of these intermediates. Furthermore, our VB analysis offers insight into the potential applications of ext...
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Electrophilic Aromatic Substitution reactions mechanistic landscape electrostatic and electric field control of reaction rates and mechanistic crossovers
Journal of the American Chemical Society, 2019Co-Authors: Frank De Proft, Thijs Stuyver, David Danovich, Sason ShaikAbstract:This study investigates the rich mechanistic landscape of the iconic Electrophilic Aromatic Substitution (EAS) reaction class, in the gas phase, in solvents, and under stimulation by oriented external electric fields. The study uses DFT calculations, complemented by a qualitative valence bond (VB) perspective. We construct a comprehensive and unifying framework that elucidates the many surprising mechanistic features, uncovered in recent years, of this class of reactions. For example, one of the puzzling issues which have attracted significant interest recently is the finding of a variety of concerted mechanisms that do not involve the formation of σ-complex intermediates, in apparent contradiction to the generally accepted textbook mechanism. Our VB modeling elucidates the existence of both the concerted and stepwise mechanisms and uncovers the root causes and necessary conditions for the appearance of these intermediates. Furthermore, our VB analysis offers insight into the potential applications of external electric fields as smart, green, and selective catalysts, which can control at will reaction rates, as well as mechanistic crossovers, for this class of reactions. Finally, we highlight how understanding of the electric fields effect on the EAS reaction could lead to the formulation of guiding principles for the design of improved heterogeneous catalysts. Overall, our analysis underscores the powerful synergy offered by combining molecular orbital and VB theory to tackle interesting and challenging mechanistic questions in chemistry.
Sason Shaik - One of the best experts on this subject based on the ideXlab platform.
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promotion energy analysis predicts reaction modes nucleophilic and Electrophilic Aromatic Substitution reactions
Journal of the American Chemical Society, 2021Co-Authors: Thijs Stuyver, Sason ShaikAbstract:To develop an approach to pre-emptively predict the existence of major reaction modes associated with a chemical system, based on exclusive consideration of reactant properties, we build herein on the valence bond perspective of chemical reactivity. In this perspective, elementary chemical reactions are conceptualized as crossovers between individual diabatic/semilocalized states. As demonstrated, the spacings between the main diabatic states in the reactant geometries-the so-called promotion energies-contain predictive information about which types of crossings are likely to occur on a potential energy surface, facilitating the identification of potential transition states and products. As an added bonus, promotion energy analysis provides direct insight into the impact of environmental effects, e.g., the presence of (polar) solvents and/or (local) electric fields, on a mechanistic landscape. We illustrate the usefulness of our approach by focusing on model nucleophilic and Electrophilic Aromatic Substitution reactions. Overall, we envision our analysis to be useful not only as a tool for conceptualizing individual mechanistic landscapes but also as a facilitator of systematic reaction-network exploration efforts. Because the emerging VB descriptors are computationally inexpensive (and can alternatively be inferred through machine learning), they could be evaluated on-the-fly as part of an exploration algorithm. The so-predicted reaction modes could subsequently be examined in detail through computationally more-demanding methods.
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Electrophilic Aromatic Substitution reactions mechanistic landscape electrostatic and electric field control of reaction rates and mechanistic crossovers
Journal of the American Chemical Society, 2019Co-Authors: Frank De Proft, Thijs Stuyver, David Danovich, Sason ShaikAbstract:This study investigates the rich mechanistic landscape of the iconic Electrophilic Aromatic Substitution (EAS) reaction class, in the gas phase, in solvents, and under stimulation by oriented external electric fields. The study uses DFT calculations, complemented by a qualitative valence bond (VB) perspective. We construct a comprehensive and unifying framework that elucidates the many surprising mechanistic features, uncovered in recent years, of this class of reactions. For example, one of the puzzling issues which have attracted significant interest recently is the finding of a variety of concerted mechanisms that do not involve the formation of σ-complex intermediates, in apparent contradiction to the generally accepted textbook mechanism. Our VB modeling elucidates the existence of both the concerted and stepwise mechanisms and uncovers the root causes and necessary conditions for the appearance of these intermediates. Furthermore, our VB analysis offers insight into the potential applications of ext...
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Electrophilic Aromatic Substitution reactions mechanistic landscape electrostatic and electric field control of reaction rates and mechanistic crossovers
Journal of the American Chemical Society, 2019Co-Authors: Frank De Proft, Thijs Stuyver, David Danovich, Sason ShaikAbstract:This study investigates the rich mechanistic landscape of the iconic Electrophilic Aromatic Substitution (EAS) reaction class, in the gas phase, in solvents, and under stimulation by oriented external electric fields. The study uses DFT calculations, complemented by a qualitative valence bond (VB) perspective. We construct a comprehensive and unifying framework that elucidates the many surprising mechanistic features, uncovered in recent years, of this class of reactions. For example, one of the puzzling issues which have attracted significant interest recently is the finding of a variety of concerted mechanisms that do not involve the formation of σ-complex intermediates, in apparent contradiction to the generally accepted textbook mechanism. Our VB modeling elucidates the existence of both the concerted and stepwise mechanisms and uncovers the root causes and necessary conditions for the appearance of these intermediates. Furthermore, our VB analysis offers insight into the potential applications of external electric fields as smart, green, and selective catalysts, which can control at will reaction rates, as well as mechanistic crossovers, for this class of reactions. Finally, we highlight how understanding of the electric fields effect on the EAS reaction could lead to the formulation of guiding principles for the design of improved heterogeneous catalysts. Overall, our analysis underscores the powerful synergy offered by combining molecular orbital and VB theory to tackle interesting and challenging mechanistic questions in chemistry.
Raymond L Funk - One of the best experts on this subject based on the ideXlab platform.
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total synthesis of lennoxamine and aphanorphine by intramolecular Electrophilic Aromatic Substitution reactions of 2 amidoacroleins
Organic Letters, 2001Co-Authors: James R Fuchs, Raymond L FunkAbstract:Intramolecular Electrophilic Aromatic Substitution reactions of 2-amidoacroleins constitute the key steps in the total syntheses of lennoxamine and aphanorphine. The aldehyde moiety of one cyclization product was transformed to a double bond, which was then engaged in a radical cyclization to produce the complete ring system of lennoxamine. The aldehyde functionality of the other cyclization product was converted to the corresponding mesylate, which underwent intramolecular displacement by a lactam enolate to furnish the ring system of aphanorphine.
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intramolecular Electrophilic Aromatic Substitution reactions of 2 amidoacroleins a new method for the preparation of tetrahydroisoquinolines tetrahydro 3 benzazepines and hexahydro 3 benzazocines
Organic Letters, 2001Co-Authors: James R Fuchs, Raymond L FunkAbstract:A variety of heterocyclic ring systems can be prepared by subjecting N-aryl-substituted 5-amido-1,3-dioxins to Lewis acids. The reactions proceed via catalyzed retrocycloadditions to afford 2-amidoacroleins and concomitant regioselective Electrophilic Aromatic Substitution reactions. The transformation is also successful using dioxins with amides that are within the incipient ring to afford the analogous lactams.
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intramolecular Electrophilic Aromatic Substitution reactions of 2 amidoacroleins a new method for the preparation of tetrahydroisoquinolines tetrahydro 3 benzazepines and hexahydro 3 benzazocines
Organic Letters, 2001Co-Authors: James R Fuchs, Raymond L FunkAbstract:[reaction: see text]. A variety of heterocyclic ring systems can be prepared by subjecting N-aryl-substituted 5-amido-1,3-dioxins to Lewis acids. The reactions proceed via catalyzed retrocycloadditions to afford 2-amidoacroleins and concomitant regioselective Electrophilic Aromatic Substitution reactions. The transformation is also successful using dioxins with amides that are within the incipient ring to afford the analogous lactams.
Yusuf Yagci - One of the best experts on this subject based on the ideXlab platform.
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visible light induced conventional step growth and chain growth condensation polymerizations by Electrophilic Aromatic Substitution
Macromolecular Rapid Communications, 2021Co-Authors: Huseyin Cem Kiliclar, Yusuf Yagci, Emirhan GencosmanAbstract:A novel visible light induced step-growth polymerization by Electrophilic Aromatic Substitution between photochemically generated carbocations and dimethoxybenzene nucleophile is described. Conventional step-growth polymerization and chain-growth condensation polymerization (CCP) mechanisms are presented. It was found that by changing the molar ratios of the monomers slightly, the CCP mechanism becomes operative and relatively higher molecular weight polymers were obtained because of the higher reactivity of the end groups of the intermediates and oligomers than that of the monomers. The possibility of grafting onto polymers containing epoxide at their side chains by photoinduced chain end activation of poly(dimethoxyphenylene methylene) is demonstrated. This study is expected to promote potential applications of the combination of photoinduced electron transfer reactions and CCP in macromolecular synthesis and material science. This article is protected by copyright. All rights reserved.
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visible light induced step growth polymerization by Electrophilic Aromatic Substitution reactions
Chemical Communications, 2021Co-Authors: Huseyin Cem Kiliclar, Cagatay Altinkok, Gorkem Yilmaz, Yusuf YagciAbstract:A novel visible light induced step-growth polymerization to form poly(phenylene methylene) by Electrophilic Aromatic Substitution reactions is described. The effect of different nucleophilic Aromatic molecules on polymerization has been investigated. The possibility of combining step-growth polymerization with conventional free radical and free radical promoted cationic polymerizations through photoinduced chain-end activation has been demonstrated. Highly fluorescent fibers of the resulting block copolymers were obtained using the electrospinning technique. The versatile photoinduced step-growth polymerization process reported herein paves the way for a new generation of polycondensates and their combination with chain polymers that cannot be obtained by conventional methods.
James R Fuchs - One of the best experts on this subject based on the ideXlab platform.
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total synthesis of lennoxamine and aphanorphine by intramolecular Electrophilic Aromatic Substitution reactions of 2 amidoacroleins
Organic Letters, 2001Co-Authors: James R Fuchs, Raymond L FunkAbstract:Intramolecular Electrophilic Aromatic Substitution reactions of 2-amidoacroleins constitute the key steps in the total syntheses of lennoxamine and aphanorphine. The aldehyde moiety of one cyclization product was transformed to a double bond, which was then engaged in a radical cyclization to produce the complete ring system of lennoxamine. The aldehyde functionality of the other cyclization product was converted to the corresponding mesylate, which underwent intramolecular displacement by a lactam enolate to furnish the ring system of aphanorphine.
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intramolecular Electrophilic Aromatic Substitution reactions of 2 amidoacroleins a new method for the preparation of tetrahydroisoquinolines tetrahydro 3 benzazepines and hexahydro 3 benzazocines
Organic Letters, 2001Co-Authors: James R Fuchs, Raymond L FunkAbstract:A variety of heterocyclic ring systems can be prepared by subjecting N-aryl-substituted 5-amido-1,3-dioxins to Lewis acids. The reactions proceed via catalyzed retrocycloadditions to afford 2-amidoacroleins and concomitant regioselective Electrophilic Aromatic Substitution reactions. The transformation is also successful using dioxins with amides that are within the incipient ring to afford the analogous lactams.
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intramolecular Electrophilic Aromatic Substitution reactions of 2 amidoacroleins a new method for the preparation of tetrahydroisoquinolines tetrahydro 3 benzazepines and hexahydro 3 benzazocines
Organic Letters, 2001Co-Authors: James R Fuchs, Raymond L FunkAbstract:[reaction: see text]. A variety of heterocyclic ring systems can be prepared by subjecting N-aryl-substituted 5-amido-1,3-dioxins to Lewis acids. The reactions proceed via catalyzed retrocycloadditions to afford 2-amidoacroleins and concomitant regioselective Electrophilic Aromatic Substitution reactions. The transformation is also successful using dioxins with amides that are within the incipient ring to afford the analogous lactams.