Understanding the mechanism of polar Diels–Alder reactions

Domingo, Luís R.; Sáez, José A.

doi:10.1039/b909611f

Cited by 460 publications

(518 citation statements)

References 56 publications

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“…In particular, the B3LYP/6-31G(d) calculations illustrate well the structure of transition states (TS) in cycloadditions between cyclopentadiene and CNA. This has been confirmed previously by the compilation of deuterium secondary kinetic isotope effects (SKIE) and results of quantum chemical calculations for polar Diels-Alder (P-DA [23] ) reaction between cyclopentadiene and (E)-2-phenylnitroethene [24]. The critical structures on the reaction paths were localized as in the case of the previously analysed reaction of (E)-2-phenyl-1-cyano-1-nitroethene with cyclopentadiene [22].…”

Section: Theoretical Exploration Of Reaction Pathssupporting

confidence: 63%

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An experimental and theoretical study of the hetero Diels–Alder reactions between (E)-2-aryl-1-cyano-1-nitroethenes and ethyl vinyl ether: one-step or zwitterionic, two-step mechanism?

Jasiński

Kubik

Łapczuk-Krygier

et al. 2014

Reac Kinet Mech Cat

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The mechanistic aspects of the hetero Diels-Alder reactions between strongly electrophilic (E)-2-aryl-1-cyano-1-nitroethenes and ethyl vinyl ether have been analyzed on the basis of kinetic experimental results as well as quantum chemical simulations of reaction paths. These reactions may theoretically proceed via one step or stepwise, zwitterionic mechanism. It was found that the conversion of addends into adducts carried out via polar, but not zwitterionic mechanism. This is confirmed by kinetic substituent and solvent effects. Subsequently, a detailed analysis of internal reaction coordinate trajectories shows that the title reactions should be considered as examples of ''two-stage one-step'' cycloadditions according to Domingo terminology.

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Section: Theoretical Exploration Of Reaction Pathssupporting

confidence: 63%

“…The large difference in the electrophilicity (Dx [ 2.7 eV) of the substrates indicates that reactions 1a-f ? 2 should be considered as P-DA reactions on the basis of Domingo terminology [23].…”

Section: Electronic Interactions Of Addentsmentioning

confidence: 99%

An experimental and theoretical study of the hetero Diels–Alder reactions between (E)-2-aryl-1-cyano-1-nitroethenes and ethyl vinyl ether: one-step or zwitterionic, two-step mechanism?

Jasiński

Kubik

Łapczuk-Krygier

et al. 2014

Reac Kinet Mech Cat

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“…The presence of electron-withdrawing substituents in the dienophile, such as 1,1-dicyanoethylene (4, DCE), favors DA reactions by lowering the activation energy [9]. The corresponding acceleration is related with the polar character of the reaction, allowing for the classification of polar Diels-Alder (P-DA) reactions [7]. This substitution breaks the symmetry of the dienophile, making the C−C σ bond formation asynchronous [9].…”

Section: (Please Insert Figure 1)mentioning

confidence: 99%

“…Electron localization function [3][4][5][6] (ELF) analysis of bonding along the intrinsic reaction coordinate (IRC) of the DA reaction of cyclopentadiene (1, Cp) with ethylene (2), which is classified as a non-polar Diels-Alder (N-DA) reaction [7], indicates that this synchronous σ bond-formation process takes place according to the following pattern (see Figure 1) [8]: i) breaking of the three π bonds present in 1 and 2; ii) formation of two pseudodiradical species; iii) formation of the two new σ bonds by coupling of two pseudodiradical species, and iv) formation of the new C-C π bond present in cycloadduct (CA) 3 at the end of the reaction. It is interesting to remark that the transition state (TS) structure associated with this N-DA reaction is located at the end of phase i; consequently, the C-C bond formation has not started yet in the TS.…”

Section: (Please Insert Chart 1)mentioning

confidence: 99%

Understanding the Bond Formation in Hetero-Diels-Alder Reactions. An ELF Analysis of the Reaction of Nitroethylene with Dimethylvinylamine

Domingo

Pérez²,

Aurell

et al. 2012

COC

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The bonding evolution in hetero-Diels-Alder (HDA) reactions has been studied by an ELF analysis of the electron reorganization along the HDA reaction between nitroethylene 6 and dimethylvinylamine (DMVA) 9 at the B3LYP/6-31G* level. This cycloaddition takes place along a two-stages one-step mechanism. In the first stage of the reaction, the C1-C6 bond is formed by coupling of two pseudoradical centers positioned at the most electrophilic carbon of nitroethylene 6 and the most nucleophilic center of DMVA 9. In the second stage, the formation of the second O4-C7 bond takes place between a pseudoradical center positioned at the C7 carbon of DMVA and some electron-density provided by the lone pairs of the O4 oxygen. This behavior is in complete agreement with analyses of the local electrophilicity and nucleophilicity indices, and the spin density of the radical anion of nitroethylene 6 and of the radical cation of DMVA 9. Finally, a relationship between the polar character of the reaction and the regioselectivity has been established.

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“…19 Notably, these reactions can be considered as polar1,3-dipolar cycloaddition (P-13DC). 20 Detailed analysis of the local electrophilicity indices on the reaction centers of nitroalkenes also revealed that the reaction was determined by the attack of nucleophilic atom of 1,3-dipole to β-position of nitroalkene, similarly as in the reactions of nitroethene with nitrones. 21 …”

Section: Resultsmentioning

confidence: 99%

Efficient synthesis of functionalized 1,2,3-triazoles by catalyst-free 1,3-dipolar cycloaddition of nitroalkenes with sodium azide

Wang¹,

Hu²,

Huang³

et al. 2012

J. Braz. Chem. Soc.

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Foi desenvolvido um protocolo simples e eficiente para a síntese de derivados de 1,2,3-triazol pela cicloadição 1,3-dipolar de nitroalquenos com azida de sódio, sem a necessidade de catalisador e sob condições brandas.A simple and efficient protocol has been developed for the synthesis of 1,2,3-triazole derivatives by catalyst-free 1,3-dipolar cycloaddition of nitroalkenes with sodium azide under mild conditions. Keywords: 1,2,3-triazoles, 1,3-dipolar cycloaddition, 3-nitrocoumarins, sodium azide, catalyst-free IntroductionFive-membered nitrogen heterocycles play an important role in biological systems. Among these, the 1,2,3-triazoles and their derivatives are of considerable interest as they possess a wide range of biological properties, such as anti-HIV, 1 anti-allergic, 2 anti-fungal, 3 anti-viral 4 and anti-microbial activity. 5 1,2,3-Triazoles are important in pharmacological applications due to its stability toward light, moisture, oxygen, and metabolism in the body. 6 In addition, these moieties are widely applied as photosensitizers, dyes, 7 and commercially employed as anti-corrosive agents 8 in industry. Owing to the importance of these compounds, a variety of methods are known in the literature for the synthesis of pyrazoles, which include the thermal 1,3-dipolar cycloaddition of azide with various alkynes 9 and cycloaddition reactions of terminal alkynes with alkyl azides using Cu(I) as catalyst. 10 In addition, these molecules can also be prepared in one-pot procedure from alkynes with azides. 11 In fact, a straightforward approach to 1,2,3-triazoles is interesting and catalystfree intermolecular 1,3-dipolar cycloaddition azides with electron-deficient alkenes to afford 1,2,3-triazoles, has been the subject of intensive research. 12 Recently, sodium azide has been used as a 1,3-dipole in 1,3-dipolar cycloaddition for the synthesis of 1,2,3-triazoles. 12 Considering the above reports and encouraged by the good results, we envisaged that 1,3-dipolar cycloaddition would be possible between the α-carbonyl-β-aryl analogs of nitroethene with sodium azide, as outlined in Scheme 1. First, the reaction was happened via 1,3-dipolar cycloaddition of nitroalkenes with sodium ion as the key step. Then, elimination of the NaNO 2 and migration of hydrogen atom afford 1,2,3-triazoles. Results and DiscussionCoumarins are important heterocycles widely present in natural products exhibiting a broad range of biological and therapeutic activities and have been the subject of intensive research. 13 Recently, we have demonstrated the usefulness of the catalyst-free intermolecular 1,3-dipolar cycloaddition of 3-nitrocoumarins in the synthesis of functionalized pyrazoles with good yields. 14 We considered that the incorporation of a 1,2,3-triazole heterocyclic unit into 3-nitrocoumarins might provide 1,2,3-triazole derivatives that have important biological and pharmaceutical activities. Thus, we turned our attention to the possible synthesis of 1,2,3-triazoles using 3-nitrocoumarins 1 as dipolarophiles for the electron-po...

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Understanding the mechanism of polar Diels–Alder reactions

Cited by 460 publications

References 56 publications

An experimental and theoretical study of the hetero Diels–Alder reactions between (E)-2-aryl-1-cyano-1-nitroethenes and ethyl vinyl ether: one-step or zwitterionic, two-step mechanism?

An experimental and theoretical study of the hetero Diels–Alder reactions between (E)-2-aryl-1-cyano-1-nitroethenes and ethyl vinyl ether: one-step or zwitterionic, two-step mechanism?

Understanding the Bond Formation in Hetero-Diels-Alder Reactions. An ELF Analysis of the Reaction of Nitroethylene with Dimethylvinylamine

Efficient synthesis of functionalized 1,2,3-triazoles by catalyst-free 1,3-dipolar cycloaddition of nitroalkenes with sodium azide

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