Molecular dynamics simulations were performed on the solvolyses of - and -norbornyl brosylate and for the "nonclassical" σ-bridged norbornyl cation in an acetic acid solution. This computational modeling of the original Winstein-Trifan experiment confirms that -solvolysis is accompanied by σ-bridging in the transition state, while -solvolysis is not; σ-bridging eventually occurs in a dynamically stepwise fashion. Simulations of the norbornyl cation in solution show typical vibrations due to zero-point and thermal vibrations but no tendency to sample localized "classical cation" geometries.
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Superelectrophilic Nonclassical Carbocations.
J Org Chem
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Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, Illinois 60115, United States.
The chemistry of dicationic and tricationic 2-norbornyl cations has been studied. A series of -heterocyclic functionalized norborneol substrates were prepared and ionization of these compounds in superacid provided superelectrophilic species. These highly charged 2-norbornyl cations were found to react with arene nucleophiles in high yields and stereoselectivity.
View Article and Find Full Text PDFMolecular Dynamics of the Norbornyl Cation in Solution and Its Generation in Winstein-Trifan Solvolysis: The Timing of Sigma Bridging.
J Org Chem
January 2024
Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States.
Molecular dynamics simulations were performed on the solvolyses of - and -norbornyl brosylate and for the "nonclassical" σ-bridged norbornyl cation in an acetic acid solution. This computational modeling of the original Winstein-Trifan experiment confirms that -solvolysis is accompanied by σ-bridging in the transition state, while -solvolysis is not; σ-bridging eventually occurs in a dynamically stepwise fashion. Simulations of the norbornyl cation in solution show typical vibrations due to zero-point and thermal vibrations but no tendency to sample localized "classical cation" geometries.
View Article and Find Full Text PDFAutomatic discovery of photoisomerization mechanisms with nanosecond machine learning photodynamics simulations.
Chem Sci
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Department of Chemistry and Chemical Biology, Northeastern University Boston MA 02115 USA
Photochemical reactions are widely used by academic and industrial researchers to construct complex molecular architectures mechanisms that often require harsh reaction conditions. Photodynamics simulations provide time-resolved snapshots of molecular excited-state structures required to understand and predict reactivities and chemoselectivities. Molecular excited-states are often nearly degenerate and require computationally intensive multiconfigurational quantum mechanical methods, especially at conical intersections.
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State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, National Center for Magnetic Resonance in Wuhan, Key Laboratory of Magnetic Resonance in Biological Systems, Wuhan Institute of Physics and Mathematics, Innovation Academy for Precision Measurement Science and Technology, Chinese Academy of Sciences, Wuhan, 430071, P. R. China.
Carbonium ions are an important class of reaction intermediates, but their dynamic evolution is difficult to be monitored by in situ techniques under experimental conditions because of their extremely short lifetime. Probably the most famous case is 2-norbornyl cation (2NB ): its existing form (classical or non-classical) had been debated for decades, until the concrete proof of non-classical geometry was achieved by X-ray crystallographic characterization at ultra-low temperature (40 K) and super acidic environment. However, we lack the understanding about 2NB at ambient conditions.
View Article and Find Full Text PDFCatalytic enantiocontrol over a non-classical carbocation.
Nat Chem
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Max-Planck-Institut für Kohlenforschung, Mülheim an der Ruhr, Germany.
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