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1.
Karolina Zawadziska Mar Ríos-Gutirrez Karolina Kula Przemysaw Woliski Barbara Mirosaw Tomasz Krawczyk Radomir Jasiski 《Molecules (Basel, Switzerland)》2021,26(22)
The regioselective zw-type [3 + 2] cycloaddition (32CA) reactions of a series of aryl-substituted nitrile N-oxides (NOs) with trichloronitropropene (TNP) have been both experimentally and theoretically studied within the Molecular Electron Density Theory (MEDT). Zwitterionic NOs behave as moderate nucleophiles while TNP acts as a very strong electrophile in these polar 32CA reactions of forward electron density flux, which present moderate activation Gibbs free energies of 22.8–25.6 kcal·mol−1 and an exergonic character of 28.4 kcal·mol−1 that makes them irreversible and kinetically controlled. The most favorable reaction is that involving the most nucleophilic MeO-substituted NO. Despite Parr functions correctly predicting the experimental regioselectivity with the most favorable O-CCCl3 interaction, these reactions follow a two-stage one-step mechanism in which formation of the O-C(CCl3) bond takes place once the C-C(NO2) bond is already formed. The present MEDT concludes that the reactivity differences in the series of NOs come from their different nucleophilic activation and polar character of the reactions, rather than any mechanistic feature. 相似文献
2.
Regiochemical aspects and the molecular mechanism of the [3 + 2] cycloaddition between nitrous oxide and conjugated nitroalkenes were evaluated on the basis of the wb97xd/6-311 + G(d) (PCM) computational study. It was found that, independently of the nature of the nitroalkene, all considered processes are realized via polar, single-step mechanisms. All attempts at the localization of hypothetical zwitterionic intermediates were unsuccessful. Additionally, the DFT computational study suggested that, in the course of the reaction, the formation of respective Δ2-4-nitro-4-R1-5-R2-1-oxa-2,3-diazolines was preferred from the kinetic point of view. 相似文献
3.
Shota Nagasaki 《Tetrahedron letters》2008,49(22):3578-3581
[2+2] Cycloaddition reactions of P2 with alkenes were predicted to have concerted paths, that is, pseudoexcitation, distorted 2πs+2πs, and 2πs+2πa processes without any interventions of intermediates. The pseudoexcitation and/or distorted 2πs+2πs paths with retention of configuration of alkenes are kinetically preferred to the 2πs+2πa path with inversion of configuration. The reactions were predicted from the appreciable difference in the calculated enthalpies of activation to be stereospecific. 相似文献
4.
Radomir Jasiński 《Phosphorus, sulfur, and silicon and the related elements》2020,195(10):871-876
AbstractThe molecular mechanism of [3?+?2] cycloaddition (32CA) process between selenyl analog of the (Z)-C,N-diphenylnitrone and nitroethene was examined on the basis of the M06-2X/6-311?+?G(d)(PCM) calculations. It was found that kinetic factors favor the formation of 4-nitro substituted cycloadducts in the reaction course. Additionally, the DFT computational study highlights the evidently polar nature of the title reaction. The mechanistic study also confirms the possibility of the existence of a zwitterionic intermediate in the reaction environment. 相似文献
5.
Jing Tang Dong-Hui Xu Xin Wang Laicai Li Xiang-Yang Liu Xin-Tong Su Jianmin Guo Bin Zhai 《International journal of quantum chemistry》2020,120(14):e26236
Here we employ density functional theory calculations to systematically investigate the underlying mechanism of Cu(OTf)2-catalyzed [3+2] cycloaddition reactions in the synthesis of CF3-substituted pyrazolidines. About eight possible initial configurations of the [3+2] reaction is considered, and all relevant reactants, transition states, and products are optimized. Based on these structures, internal reaction coordinate paths, and wavefunction analysis results, we conclude that the Cu(OTf)2-catalyzed [3+2] cycloaddition follows a concerted asynchronous mechanism. The C N bond forms immediately after the formation of the C C bond. Among the eight reaction paths, the energy barrier for the [3+2] reaction that leads to the CF3-substituted syn-pyrazolidine is the lowest, ∼5.4 kcal/mol, which might result in the diastereoselectivity that is observed in the experiment. This work not only gives the detailed mechanism of the Cu(OTf)2-catalyzed [3+2] cycloaddition but can also be helpful for the future designation of Cu(OTf)2-based cycloaddition processes. 相似文献
6.
Beatriz Lantaño Esteban Ariel Ugliarolo Graciela Yolanda Moltrasio 《Tetrahedron》2008,64(18):4090-4102
We report the single step synthesis of several 3-arylindanes and related compounds via a formal [3+2] cycloaddition. A study of the influence of the aromatic ring substitution pattern on the reaction was carried out. 相似文献
7.
Fernanda M. Ribeiro Laia 《Tetrahedron letters》2009,50(45):6180-2356
The reactivity of buta-2,3-dienoates toward aziridines is reported. Allenoates react as 2π-component in the [3+2] cycloaddition with the azomethine ylide generated from cis-1-benzyl-2-benzoyl-3-phenylaziridine affording 4-methylenepyrrolidines in a site-, regio-, and stereoselective fashion. Under conventional thermolysis, cis- and trans-2-benzoyl-1-cyclohexyl-3-phenylaziridines showed a different reactivity. These aziridines participate in formal [3+2] cycloadditions with allenes via C-N bond cleavage of the three-membered ring leading to functionalized pyrroles. 相似文献
8.
Shū Kobayashi Ryoji HirabayashiHaruka Shimizu Haruro IshitaniYasuhiro Yamashita 《Tetrahedron letters》2003,44(16):3351-3354
[3+2] Cycloaddition between hydrazones and olefins was accelerated in the presence of a stoichiometric amount of BF3·OEt2 or a catalytic amount of Zr(OTf)4, Hf(OTf)4, or Sc(OTf)3 under mild conditions. The corresponding pyrazolidine derivatives were obtained in moderate to high yields using this novel [3+2] Lewis acid catalysis. 相似文献
9.
Bing-Feng Sun Chao-Lei Wang Rui DingJin-Yi Xu Guo-Qiang Lin 《Tetrahedron letters》2011,52(17):2155-2158
A concise enantioselective synthesis of diversely functionalized advanced intermediates comprising the tricyclic skeleton of englerin A and related oxygen-bridged guaianes has been successfully accomplished, which features a Harmata organocatalytic [4+3] cycloaddition reaction. 相似文献
10.
We describe the synthesis of a series of conformationally constrained nicotine analogues 2-5 from appropriate pyridine-containing enals, featuring an intramolecular azomethine ylide-alkene [3+2] cycloaddition. The objective of the current project is to develop new selective nAChRs-targeting ligands. Of the nicotine analogues that we have studied, the conformation-restricting ring B unit can be either a five-membered carbocycle, or a six-membered carbocycle or heterocycle. The present work constitutes a general method for rapid assembly of other related tricyclic nicotine analogues. 相似文献
11.
Methylenecyclopropanes react with activated aldehydes or ketones in the presence of various Lewis acids to give the corresponding [3+2] cycloaddition products having tetrahydrofuran (THF) skeleton in good yields and in some cases with high stereoselectivity. 相似文献
12.
A model study toward total synthesis of madreporanone, a novel diterpene isolated from Azorella madreporica, was investigated. The [3.3.0] bicyclic core of madreporanone bearing a cis-configured isopropyl group and two vicinal quaternary carbon centers was stereoselectively constructed via an intramolecular Rh-catalyzed [3 + 2] cycloaddition in a single step. 相似文献
13.
《Comptes Rendus Chimie》2015,18(12):1277-1283
A theoretical study of the [3+2] cycloaddition (32CA) reaction between benzonitrile sulfide BNS1 and trichloroacetonitrile TCAN2 at the MPWB1 K/6-311G(d) level was undertaken. Among two feasible C1N5 and C1C4 regioisomeric channels, the former is completely preferred, in the presence of toluene, over the latter, both kinetically, ΔΔGactivation = 17.5 kcal/mol, and thermodynamically, ΔΔGreaction = –12.8 kcal/mol, in excellent agreement with experimental outcomes. The strong global electrophilic and nucleophilic characters found for TCAN2 and BNS1, respectively, allow the studied 32CA reaction to take place via a polar process. Interestingly, the analysis of the TSs geometries clarifies that in the case under study, regioselectivity is controlled by destabilizing steric repulsion interactions rather than electronic ones. The ELF topological patterns indicate that while the formation of S3C4 single bond takes place exactly according to Domingo's model, that of the C1N5 single bond is a direct consequence of the nucleophilic attack of the C5 carbon atom on the N5 nitrogen atom supporting a two-stage one-step molecular mechanism. 相似文献
14.
Katarzyna Mitka Katarzyna Fela Aleksandra Olszewska Radomir Jasiski 《Molecules (Basel, Switzerland)》2021,26(23)
The molecular mechanism of the [3 + 2] cycloaddition reaction between C-arylnitrones and perfluoro 2-methylpent-2-ene was explored on the basis of DFT calculations. It was found that despite the polar nature of the intermolecular interactions, as well as the presence of fluorine atoms near the reaction centers, all reactions considered cycloaddition proceed via a one-step mechanism. All attempts for the localization of zwitterionic intermediates on the reaction paths were not successful. Similar results were obtained regardless of the level of theory applied. 相似文献
15.
16.
Masataka Nakahara Prof. Kengo Hanaya Prof. Takeshi Sugai Prof. Shuhei Higashibayashi 《ChemistryOpen》2021,10(6):627-629
Dearomative heterocyclic [4+2] cycloaddition between the N-(2,4-dinitrophenyl)pyridinium ion of nicotinamide and an enol ether was analyzed by Density Functional Theory (DFT) calculations. The calculation revealed that the reaction undergoes stepwise bond formation rather than occurring in a concerted manner. The experimental products were found to be both kinetically and thermodynamically favored. The calculated transition states and intermediate suggested that the high diastereoselectivity is derived from the electrostatic interaction between the 2-nitro group of the pyridinium ion and the hydrogen of the enol ether. 相似文献
17.
《Comptes Rendus Chimie》2016,19(3):306-313
A simple, mild and efficient method is developed for the synthesis of 5-substituted 1H-tetrazoles. Out of three used Pb(II) catalysts, lead chloride (PbCl2) has been found to be an efficient catalyst for [3+2] cycloaddition of NaN3 with aromatic and aliphatic nitriles to afford 5-substituted 1H-tetrazoles. The catalyst is reusable up to four cycles with consistent activity. The cost effectiveness and easy availability of the catalyst, simple methodology, excellent yield and easy work-up are the additional advantages. 相似文献
18.
[2+3] Cycloaddition of 3-nitropropene-1 with C,C,N-triphenylnitrone leads to a mixture of 5-nitromethyl-2,3,3-triphenylisoxazolidine
and 5-methyl-4-nitro-2,3,3-triphenylisoxazolidine. The results obtained can be explained assuming that 3-nitropropene-1 isomerizes
to 1-nitropropene-1 under reaction conditions.
Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1545–1548, October, 2006. 相似文献
19.
Sylvain Celanire Frederic Marlin Jack E. Baldwin Robert M. Adlington 《Tetrahedron》2005,61(12):3025-3032
The synthesis of 3,11-dioxatricyclo[5.3.1.01,5]undeca-5,9-dien-8-ones is reported from suitable 5-substituted furfuryl alcohols bearing an acetylenic side-chain. Successive peracid-mediated oxidative rearrangement of furan carbinols and base-assisted intramolecular 1,3-dipolar cycloaddition afforded oxygen-bridged tricyclo-undecane derivatives. Stereoselective transformations of cycloadducts are also discussed. 相似文献
20.
Jianwu Xie 《Tetrahedron letters》2008,49(48):6910-6913
A chiral thiourea catalyst possessing an amine function catalyzes an asymmetric [3+2] cycloaddition of azomethine ylides to nitroolefins to provide highly functionalized pyrrolidines with high diastereo- and enantioselectivities (up to 98:1:1 dr, 92% ee). The reaction proceeds in a stepwise manner consisting of Michael addition and subsequent intramolecular aza-Henry reaction. Both reactions are promoted by the thiourea catalyst, and the reaction rate of the latter step is efficiently enhanced by the addition of 2,2,2-trifluoroethanol. 相似文献