Relevant bibliographies by topics / Non-Classical Carbocation

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Academic literature on the topic 'Non-Classical Carbocation'

Author: Grafiati
Published: 24 May 2025
Last updated: 29 May 2025

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Journal articles on the topic "Non-Classical Carbocation"

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Properzi, Roberta, Philip S. J. Kaib, Markus Leutzsch, Gabriele Pupo, Raja Mitra, Chandra Kanta De, Lijuan Song, Peter R. Schreiner, and Benjamin List. "Catalytic enantiocontrol over a non-classical carbocation." Nature Chemistry 12, no. 12 (September 28, 2020): 1174–79. http://dx.doi.org/10.1038/s41557-020-00558-1.

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Skvorcova, M., and A. Jirgensons. "Intramolecular cyclopropylmethylation via non-classical carbocations." Organic & Biomolecular Chemistry 15, no. 33 (2017): 6909–12. http://dx.doi.org/10.1039/c7ob01721a.

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Hanson, James R. "Skeletal Rearrangements of Rings C and D of the Kaurene and Beyerene Tetracyclic Diterpenoids." Journal of Chemical Research 42, no. 4 (April 2018): 175–80. http://dx.doi.org/10.3184/174751918x15233039624478.

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The skeletal rearrangement of the bicyclo[3.2.1]octane portion of rings C and D of the kaurene and beyerene tetracyclic diterpenoids are reviewed, revealing the tendency of the secondary carbocations to rearrange to tertiary carbocations with the eventual preferential formation of bicyclo[2.2.2]octanes. Under acid-catalysed conditions the variations in the products with the nucleophilicity of the counter ions suggest that the intervention of discrete rather than completely delocalised non-classical carbonium ions may be contributing to the reaction pathway.
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Alkorta, Ibon, José Luis M. Abboud, Esther Quintanilla, and Juan Z. Dávalos. "A theoretical study of (old and new) non-classical carbocations derived from cyclic saturated hydrocarbons." Journal of Physical Organic Chemistry 16, no. 8 (August 2003): 546–54. http://dx.doi.org/10.1002/poc.630.

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Allwohn, Jürgen, Ralf Hunold, Monika Pilz, Rolf-Günter Müller, Werner Massa, and Armin Berndt. "Nachweis starker C – Sn-Hyperkonjugation über Kristallstruktur und NMR-Daten eines C-Stannylmethylenborans / Evidence for Strong C–Sn-Hyperconjugation by Crystal Structure and NMR Data of a C-Stannylmethyleneborane." Zeitschrift für Naturforschung B 45, no. 3 (March 1, 1990): 290–98. http://dx.doi.org/10.1515/znb-1990-0304.

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Strong C—Sn hyperconjugation in C-stannylmethyleneborane 3 is indicated by (1) a small B—sp2C—Sn bond angle (105.6°), (2) a long sp2C—Sn bond (216 pm), (3) a very short B=C double bond (131 pm), (4) a very small coupling constant 1J(119Sn-13C) = 125 Hz for the sp2C—Sn bond and (5) shielding of the boron atom of the B=C double bond by 20 ppm as compared to methyleneboranes without strong hyperconjugation. The boron atoms of the B=C double bond of 3 and related methyleneboranes act as π-donor and σ-acceptor, the substituents X at the carbon atom of the B=C double bond as π-acceptors and, through their C—X σ-bonds, as σ-donors. The partly bridged methyleneborane 3 closes the gap between unbridged and bridged methyleneboranes. Relationships to non-classical carbocations are pointed out.
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García-Padilla, Eduardo, Imma Escofet, Feliu Maseras, and Antonio M. Echavarren. "The Puzzling Structure of the Key Intermediates in Gold(I) Catalyzed Cyclizations of Enynes and Allenenes." ChemPlusChem, November 21, 2023. http://dx.doi.org/10.1002/cplu.202300502.

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We identify the dominant structures of the intermediates of gold(I)‐catalyzed cyclizations of 1,5‐enynes and 1,5‐allenenes through computational analysis as gold(I) cyclopropylcarbenes, endocyclic vinylgold complexes and previously unreported non‐classical carbocationic minima. In contrast to 1,6‐enynes, the exocyclic carbocations are found to be less stable. Cyclopropylcarbene structures are consistently favoured as the most stable intermediates for all studied substitution patterns. We validate the computational methods used by using DLPNO‐CCSD(T) energies as a benchmark, indicating that the B3LYP‐D3 and M06‐D3 functionals are most accurate for energy determination, while NPA charges are mostly insensitive to functional. The evolution of a 1,6‐enyne in a single‐cleavage or double‐cleavage rearrangement is attributed to the barrierless evolution of a common cylopropylgold(I) carbocation non‐stationary geometry. Our findings provide insights into reaction pathways and substrate dependence of the cycloisomerization processes.
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Chakladar, Saswati, Yi Wang, Thomas Clark, Lydia Cheng, Shirley Ko, David J. Vocadlo, and Andrew J. Bennet. "A mechanism-based inactivator of glycoside hydrolases involving formation of a transient non-classical carbocation." Nature Communications 5, no. 1 (December 2014). http://dx.doi.org/10.1038/ncomms6590.

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Shi, Hong-Song, Jun-An Ma, Ilan Marek, and Fa-Guang Zhang. "Fe‐Catalyzed Stereospecific Intramolecular Friedel–Crafts‐type Reaction of Fluoroalkyl Cyclopropyl Carbinols via Non‐classical Carbocation." Advanced Synthesis & Catalysis, March 11, 2025. https://doi.org/10.1002/adsc.202500242.

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Here we describe a Fe‐catalyzed stereospecific intramolecular Friedel–Crafts‐type reaction of polysubstituted stereodefined fluoroalkyl cyclopropyl carbinols. This transformation provides access to a series of fluoroalkyl group‐substituted dihydro‐1H‐indenols bearing three continuous stereogenic centers including two congested tetra‐substituted stereocenters. The key to the realization of this reaction relies on the electronic destabilizing effect of fluoroalkyl group to tune the stability and reactivity of non‐classical cyclopropyl‐carbinyl cation intermediate. Functional group interconversions of the obtained diastereomerically pure dihydro‐1H‐indenols further demonstrated the synthetic utility of this rationally designed reaction.
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Pérez-Guevara, Raquel, Luis Sarandeses, Rosana Alvarez, M. Montserrat Martínez, and José Pérez Sestelo. "Stereospecific Indium(III)‐catalysed tandem cycloisomerization of functionalized 1,6‐enynes: scope and mechanistic insights." Advanced Synthesis & Catalysis, December 24, 2023. http://dx.doi.org/10.1002/adsc.202301329.

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Tandem cycloisomerization reactions of functionalized 1,6‐enynes under indium(III) catalysis are described. This atom‐economic transformation proceeds smoothly with 5‐exo‐dig regioselectivity using commercial In(III) halides and 1,6‐enynes furnished with alcohol, carboxylic acid or amine functional groups to give bicyclic structures in good yields and diastereoselectivities. The reaction with enynals involves a three–step mechanism to give an oxatricycle and a conjugated 1,3‐diene. In the absence of the internal nucleophile the enyne cycloisomerization evolves through a skeletal rearrangement or a cyclopropanation reaction after the regioselective 5‐exo‐dig cyclization. The 1,6‐enyne cycloisomerization is stereospecific and the stereoselectivity appears to be independent of the internal nucleophile. Experimental data support a common reaction mechanism involving an initial alkyne electrophilic π‐coordination of In(III) followed by Markovnikov electrophilic alkene addition and ring‐closure by nucleophilic attack. DFT studies hold up a stepwise mechanism involving the formation of a chiral non‐classical carbocation intermediate that determines the diastereoselectivity of this tandem cycloisomerization reaction.
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Omdim, Irene Nadage, Kenneth Oben Eyong, Blandine Marlysse Wache Ouahouo, Herve Landry Ketsemen, Thomas Werner, Michael Hermann K. Kamdem, Derek Tantoh Ndinteh, et al. "Selective Electrophile‐Promoted Cyclization Reactions of Lapachol and Evaluation of Bioactive Naphthoquinones Against Cancer Cell Lines." Journal of Heterocyclic Chemistry, December 10, 2024. https://doi.org/10.1002/jhet.4935.

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ABSTRACTCyclic ether‐fused tricyclic naphthoquinones are major pharmacophores because of their biological activities. The methodology of construction is either by inter or intra‐molecular cyclization of functionalized naphthoquinones. This reaction includes a wide range of reagents from classical Brønsted to Lewis acids. The choice of appropriate reagent and reaction conditions against the substrate is the key to accomplishing the regio‐ and/or stereo‐selective synthesis of these compounds, though it seems difficult at first glance to decide how because numerous numbers of actual examples have been presented. To have a deeper insight into the mechanism of cyclization under acid conditions, lapachol 1 was subjected to electrophilic entities: Brønsted acids (H2SO4, HCl, H3PO4, HNO3, HCOOH, CH3COOH, HOOCCH2COOH), Lewis acids (AlCl3, FeCl3, ZnCl2) nitrogenous cations (NO+, NO2+), carbocation (CH3CO+), neutral polarized molecules (CH3COCl, CH3COOCH3), neutral polarizable molecules (Br2, I2), oxidant promoted cyclization (DDQ, CAN, Peroxides), and reaction conditions. A series of Naphthoquinones based on the Isoprenyl‐1,4‐naphthoquinone (Lapachol), naphtho[1,2‐b]furan‐4,5‐dione (nor β‐lapachone), naphtho[2,3‐b]pyran‐5,10‐dione (α‐lapachone), naphtho[1,2‐b]pyran‐5,6‐dione (β‐lapachone), and naphtho[2,3‐b]furan‐4,9‐dione (2‐acetyl furonaphthoquinone) skeletons were selectively synthesized. By looking at our result, there are characteristic trends of cyclized adducts depending on which reagents were used. The synthesized compounds were evaluated for their biological activity against the MDA‐MB‐231 breast cancer, HT‐29 MTX colon cancer, and non‐transformed mammary epithelial cell lines at concentrations of 1 μM, 10 μM, and 100 μM. The result indicated that lapachol and β‐lapachone skeletons were the most active at 10 μM and 100 μM especially 3‐hydroxy‐β‐lapachone 8 with interesting growth stimulatory effect on cancer cell lines, but not the non‐transformed cells.
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Dissertations / Theses on the topic "Non-Classical Carbocation"

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Myronova, Veronika. "Νοvel Apprοaches fοr the Stereοselective Cοnstructiοn Οf Challenging Fluοrinated Μοlecules." Electronic Thesis or Diss., Normandie, 2025. http://www.theses.fr/2025NORMR008.

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Cette étude de doctorat porte sur la construction de molécules présentant des stéréocentres adjacents incluant des motifs fluorés, un défi actuel en chimie organique. Dans un premier temps, nous avons développé des carbométallations de cyclopropènes contenant un groupe CF3, sous catalyse au cuivre, permettant d’obtenir des cyclopropanes hautement substitués avec une excellente régio- et diastéréosélectivité. La carbométallation se déroule avec une préférence diastéréofaciale anti par rapport au groupe CF3. La configuration relative a été déterminée par RMN du proton et confirmée par diffraction des rayons X sur monocristal.Ensuite, nous avons démontré que les dérivés CF3-cyclopropyl carbinol subissent une substitution nucléophile régio- et diastéréosélective au niveau du carbone quaternaire, conduisant à des produits acycliques sous forme de diastéréomères uniques. Cette étude propose une voie de synthèse pratique vers des chlorures, bromures et fluorures tertiaires, présentant deux stéréocentres adjacents décorés d’un halogène et d’un motif trifluorométhyle. Ces produits sont diastéréomériquement purs et peuvent être obtenus en seulement quatre étapes synthétiques à partir d’alcynes commerciaux
This PhD study focuses on the construction of molecules featuring adjacent stereocenters that include fluorinated motifs, an on-going challenge in organic chemistry. Firstly, we developed copper-mediated carbometalations of CF3-containing cyclopropenes, affording highly substituted cyclopropanes with excellent regio- and diastereoselectivity. The carbometalation proceeds with anti diastereofacial preference towards the CF3 group. The relative configuration was determined by ¹H NMR and confirmed by single-crystal X-ray diffraction.Finally, we demonstrated that CF3-cyclopropyl carbinol derivatives undergo regio- and diastereoselective nucleophilic halogenations (F, Cl, Br) at the quaternary carbon center, yielding acyclic products as single diastereomers. This study presents a practical synthetic pathway to tertiary alkyl chlorides, bromides, and fluorides, featuring two adjacent stereocenters decorated with halogens and a trifluoromethyl motif. These products are diastereomerically pure and can be obtained in just four synthetic steps from commercially available alkynes
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