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Keywords = vinylcyclopropane

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19 pages, 5424 KiB  
Article
Insights into the Mechanism, Regio-/Diastereoselectivities and Ligand Role of Nickel-Initiated [3+2] Cycloadditions between Vinylcyclopropane and N-Tosylbenzaldimine
by Weihua Mu, Lin Zhu, Shuya Xia, Xue Tan, Liangfei Duan, Guanghao Meng and Guo Liu
Catalysts 2024, 14(1), 82; https://doi.org/10.3390/catal14010082 - 18 Jan 2024
Cited by 1 | Viewed by 1739
Abstract
Density functional theory (DFT) was employed to explore the reaction mechanism, regio- and diastereoselectivities of nickel-initiated [3+2] cycloaddition between vinylcyclopropane (VCP) and N-tosylbenzaldimine assisted by phosphine ligands. Four different binding modes of the nickel center to VCP substrate were explored during the [...] Read more.
Density functional theory (DFT) was employed to explore the reaction mechanism, regio- and diastereoselectivities of nickel-initiated [3+2] cycloaddition between vinylcyclopropane (VCP) and N-tosylbenzaldimine assisted by phosphine ligands. Four different binding modes of the nickel center to VCP substrate were explored during the ring-opening of VCP, among which the C,C_anti and C,C_syn modes were verified to be the most accessible ones. Further explorations about four different phosphine ligand-assisted reactions based on the two most probable binding modes show that the difference in binding mode of bi- and monodentate phosphine ligands can vary the optimal reaction pathway, especially in the [3+2] cycloaddition process between the ring-opened intermediate and N-tosylbenzaldimine. The formation of C–C and C–N bonds between N-tosylbenzaldimine and the ring-opened intermediate through [3+2] cycloaddition is found to be stepwise, with the former acting as the rate-determining step (RDS) in most cases. Computed free energy barriers of RDS transition states on the optimal path I or II not only give out good predictions for reaction rates and half-lives, but also provide reasonable explanations for the major generation of cis-pyrrolidine. Noncovalent interaction analyses of key stationary points suggest the rate is influenced by both electronic effects and steric hindrance, while the diastereoselectivity is mainly controlled by electronic effects. Full article
(This article belongs to the Special Issue Organometallic Homogeneous Catalysis)
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14 pages, 1620 KiB  
Article
Synergistic Palladium-Phosphoric Acid Catalysis in (3 + 2) Cycloaddition Reactions between Vinylcyclopropanes and Imines
by Vasco Corti, Enrico Marcantonio, Martina Mamone, Alessandro Giungi, Mariafrancesca Fochi and Luca Bernardi
Catalysts 2020, 10(2), 150; https://doi.org/10.3390/catal10020150 - 24 Jan 2020
Cited by 12 | Viewed by 4661
Abstract
The palladium-catalyzed (3 + 2) cycloaddition reaction between vinylcyclopropanes (VCPs) bearing geminal EWG’s and imines represents a straightforward and flexible entry to polysubstituted pyrrolidine derivatives. In this paper, we demonstrate that using a synergistic catalysis approach, based on the combination of phosphoric acid [...] Read more.
The palladium-catalyzed (3 + 2) cycloaddition reaction between vinylcyclopropanes (VCPs) bearing geminal EWG’s and imines represents a straightforward and flexible entry to polysubstituted pyrrolidine derivatives. In this paper, we demonstrate that using a synergistic catalysis approach, based on the combination of phosphoric acid and palladium catalysts, it is possible to engage for the first time N-aryl and N-benzyl imines in this cycloaddition reaction. A range of polysubstituted pyrrolidines is obtained with moderate to good yields and diastereoselectivities, using a simple palladium species (Pd(PPh3)4) and an archetypical phosphoric acid as catalyst combination. A two-step scheme which exploits the same palladium catalyst for two consecutive and mechanistically distinct reactions (the cycloaddition and a Suzuki–Miyaura cross-coupling) is also presented. This synergistic catalysis approach is well posited for the development of the enantioselective version of this reaction. A screening of common BINOL-derived chiral phosphoric acids as catalyst component identified a species giving the product with moderate, yet promising, enantioselectivity (64% ee). Full article
(This article belongs to the Special Issue Exploring Hydrogen Bond and Bronsted Acid Catalysis)
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17 pages, 5246 KiB  
Article
Characterization of Polysulfides, Polysulfanes, and Other Unique Species in the Reaction between GSNO and H2S
by Murugaeson R Kumar and Patrick J Farmer
Molecules 2019, 24(17), 3090; https://doi.org/10.3390/molecules24173090 - 26 Aug 2019
Cited by 15 | Viewed by 4535 | Correction
Abstract
Glutathione-based products, GSnX, of the reaction of hydrogen sulfide, H2S, S-nitroso glutathione, and GSNO, at varied stoichiometries have been analyzed by liquid chromatography high-resolution mass spectrometry (LC-HRMS) and chemical trapping experiments. A wide variety of glutathione-based species with catenated [...] Read more.
Glutathione-based products, GSnX, of the reaction of hydrogen sulfide, H2S, S-nitroso glutathione, and GSNO, at varied stoichiometries have been analyzed by liquid chromatography high-resolution mass spectrometry (LC-HRMS) and chemical trapping experiments. A wide variety of glutathione-based species with catenated sulfur chains have been identified including sulfanes (GSSnG), sulfides (GSSnH), and sulfenic acids (GSnOH); sulfinic (GSnO2H) and sulfonic (GSnO3H) acids are also seen in reactions exposed to air. The presence of each species of GSnX within the original reaction mixtures was confirmed using Single Ion Chromatograms (SICs), to demonstrate the separation on the LC column, and given approximate quantification by the peak area of the SIC. Further, confirmation for different GSnX families was obtained by trapping with species-specific reagents. Several unique GSnX families have been characterized, including bridging mixed di- and tetra-valent polysulfanes and internal trithionitrates (GSNHSnH) with polysulfane branches. Competitive trapping experiments suggest that the polysulfane chains are formed via the intermediacy of sulfenic acid species, GSSnOH. In the presence of radical trap vinylcyclopropane (VCP) the relative distributions of polysulfane speciation are relatively unaffected, suggesting that radical coupling is not a dominant pathway. Therefore, we suggest polysulfane catenation occurs via reaction of sulfides with sulfenic acids. Full article
(This article belongs to the Special Issue Signaling Molecules: Hydrogen Sulfide and Polysulfide)
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17 pages, 389 KiB  
Article
Gas Phase Thermal Reactions of exo-8-Cyclopropyl-bicyclo[4.2.0]oct-2-ene (1-exo)
by Phyllis A. Leber, Anthony J. Nocket, William Hancock-Cerutti, Christopher Y. Bemis, Wint Khant Khine, Joseph A. Mohrbacher III and John E. Baldwin
Molecules 2014, 19(2), 1527-1543; https://doi.org/10.3390/molecules19021527 - 27 Jan 2014
Cited by 2 | Viewed by 9035
Abstract
The title compound 1-exo (with minor amounts of its C8 epimer 1-endo) was prepared by Wolff-Kishner reduction of the cycloadduct of 1,3-cyclohexadiene and cyclopropylketene. The [1,3]-migration product 2-endo was synthesized by efficient selective cyclopropanation of endo-5-vinylbicyclo[2.2.2]oct-2-ene at the [...] Read more.
The title compound 1-exo (with minor amounts of its C8 epimer 1-endo) was prepared by Wolff-Kishner reduction of the cycloadduct of 1,3-cyclohexadiene and cyclopropylketene. The [1,3]-migration product 2-endo was synthesized by efficient selective cyclopropanation of endo-5-vinylbicyclo[2.2.2]oct-2-ene at the exocyclic π-bond. Gas phase thermal reactions of 1-exo afforded C8 epimerization to 1-endo, [1,3]- migrations to 2-exo and 2-endo, direct fragmentation to cyclohexadiene and vinylcyclopropane, and CPC rearrangement in the following relative kinetic order: kep > k13 > kf > kCPC. Full article
(This article belongs to the Special Issue Gas Phase Reactions)
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