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. Density functional theory computational studies suggest that increasing positive charge on the structures tends to enhance the degree of nonclassical (or 3-center-2-electron) bonding through separation of the cationic charges.
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Superelectrophilic Nonclassical Carbocations.
J Org Chem
July 2024
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.
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Angew Chem Int Ed Engl
February 2021
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.
Carbocations can be categorized into classical carbenium ions and non-classical carbonium ions. These intermediates are ubiquitous in reactions of both fundamental and practical relevance, finding application in the petroleum industry as well as the discovery of new drugs and materials. Conveying stereochemical information to carbocations is therefore of interest to a range of chemical fields.
View Article and Find Full Text PDFCrystal Structure Determination of the Pentagonal-Pyramidal Hexamethylbenzene Dication C (CH ).
Angew Chem Int Ed Engl
January 2017
Freie Universität Berlin, Institut für Chemie und Biochemie-Anorganische Chemie, Fabeckstraße 34-36, 14195, Berlin, Germany.
In contrast to the well-known 2-norbornyl cation, the structure of which was a matter of long debate until its pentacoordinated nature was recently proven by an X-ray structure, the pentagonal-pyramidal dication of hexamethylbenzene has received considerably less attention. This species was first prepared by Hogeveen in 1973 at low temperatures in magic acid (HSO F/SbF ), for which he proposed a non-classical structure (containing a hexacoordinated carbon) based on NMR spectroscopy and reactivity studies, but no X-ray crystal structure has been reported. C (CH ) can be obtained through the dissolution of hexamethyl Dewar benzene epoxide in HSO F/SbF and crystallized as the SbF salt upon addition of excess anhydrous hydrogen fluoride.
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Angew Chem Int Ed Engl
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Department of Chemistry, University of Georgia, Athens, GA 30602 (USA) http://maduncan.myweb.uga.edu.
In an attempt to produce the 2-norbornyl cation (2NB(+)) in the gas phase, protonation of norbornene was accomplished in a pulsed discharge ion source coupled with a supersonic molecular beam. The C7H11(+) cation was size-selected in a time-of-flight mass spectrometer and investigated with infrared laser photodissociation spectroscopy using the method of "tagging" with argon. The resulting vibrational spectrum, containing sharp bands in the C-H stretching and fingerprint regions, was compared to that predicted by computational chemistry.
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