Understanding the molecular mechanism in a regiospecific [3 + 2] cycloaddition reaction including C–O and C–S interactions: an ELF topological analysis

RSC Advances ◽  
2015 ◽  
Vol 5 (89) ◽  
pp. 72959-72970 ◽  
Author(s):  
Saeedreza Emamian
Keyword(s):  
Molecular Mechanism ◽  
Topological Analysis ◽  
Cycloaddition Reaction ◽  
One Step ◽  
Step Mechanism

Regiospecific 32CA reaction of nitrone 10 toward thioketone 11 takes place via a non-concerted one-step mechanism confirmed by ELF analysis.

scholarly journals On the Question of Zwitterionic Intermediates in the [3 + 2] Cycloaddition Reactions between C-arylnitrones and Perfluoro 2-Methylpent-2-ene

Molecules ◽  
2021 ◽  
Vol 26 (23) ◽  
pp. 7147
Author(s):  
Katarzyna Mitka ◽  
Katarzyna Fela ◽  
Aleksandra Olszewska ◽  
Radomir Jasiński
Keyword(s):  
Dft Calculations ◽  
Molecular Mechanism ◽  
Intermolecular Interactions ◽  
Cycloaddition Reaction ◽  
Reaction Centers ◽  
Cycloaddition Reactions ◽  
Reaction Paths ◽  
One Step ◽  
Step Mechanism

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.

scholarly journals Unveiling the Intramolecular Ionic Diels–Alder Reactions within Molecular Electron Density Theory

Chemistry ◽  
2021 ◽  
Vol 3 (3) ◽  
pp. 834-853
Author(s):  
Luis R. Domingo ◽  
Mar Ríos-Gutiérrez ◽  
María José Aurell
Keyword(s):  
Electron Density ◽  
Electronic Structures ◽  
Activation Enthalpy ◽  
Topological Analysis ◽  
Chair Conformation ◽  
Diels Alder ◽  
Molecular Electron ◽  
One Step ◽  
Molecular Electron Density Theory ◽  
Step Mechanism

The intramolecular ionic Diels–Alder (IIDA) reactions of two dieniminiums were studied within the Molecular Electron Density Theory (MEDT) at the ωB97XD/6-311G(d,p) computational level. Topological analysis of the electron localization function (ELF) of dieniminiums showed that their electronic structures can been seen as the sum of those of butadiene and ethaniminium. The superelectrophilic character of dieniminiums accounts for the high intramolecular global electron density transfer taking place from the diene framework to the iminium one at the transition state structures (TSs) of these IIDA reactions, which are classified as the forward electro density flux. The activation enthalpy associated with the IIDA reaction of the experimental dieniminium, 8.7 kcal·mol−1, was closer to that of the ionic Diels–Alder (I-DA) reaction between butadiene and ethaniminium, 9.3 kcal·mol−1. However, the activation Gibbs free energy of the IIDA reaction was 12.7 kcal·mol−1 lower than that of the intermolecular I-DA reaction. The strong exergonic character of the IIDA reaction, higher than 20.5 kcal·mol−1, makes the reaction irreversible. These IIDA reactions present a total re/exo and si/endo diastereo selectivity, which is controlled by the most favorable chair conformation of the tetramethylene chain. ELF topological analysis of the single bond formation indicated that these IIDA reactions take place through a non-concerted two-stage one-step mechanism. Finally, ELF and atoms-in-molecules (AIM) topological analyses of the TS associated with the inter and intramolecular processes showed the great similarity between them.

scholarly journals An electron localization function analysis of the molecular mechanism and the C–O bond formation in the [3+2] cycloaddition reaction involving zwitterionic type between a nitrone and an electron deficient ethyne

2019 ◽  
Vol 45 ◽  
pp. 146867831982574
Author(s):  
Abdelilah Benallou ◽  
Habib El Alaoui El Abdallaoui ◽  
Hocine Garmes
Keyword(s):  
Electron Density ◽  
Function Analysis ◽  
Bond Formation ◽  
Cycloaddition Reaction ◽  
Intrinsic Reaction Coordinate ◽  
Dimethyl Acetylenedicarboxylate ◽  
Central Carbon ◽  
One Step ◽  
Free Activation Energy ◽  
Step Mechanism

The mechanistic nature of a [3+2] cycloaddition reaction involving zwitterionic species has been investigated, and the changes of electron density related to the O–C and C–C bond formation along the intrinsic reaction coordinate have been characterized. This polar [3+2] cycloaddition reaction, which takes place through a non-concerted two-stage one-step mechanism, proceeds with a moderate Gibbs free activation energy of 21 kcal mol−1. The reaction begins by the creation of a pseudoradical centre at the central carbon, first on the dimethyl acetylenedicarboxylate, and second on the nitrone framework. This immediately favours the formation of the first O–C single bond by donation of some electron density of the oxygen atom lone pairs, which represents the most attractive centre in this cycloaddition reaction.

A Combined Topological ELF, NCI and QTAIM Study of Mechanism and Hydrogen Bond Controlling the Selectivity of the IMDC Reaction of Nitrone-alkene Obtained from m-allyloxybenzaldehyde

2020 ◽  
Vol 17 (4) ◽  
pp. 260-267 ◽  
Author(s):  
Fouad Chafaa ◽  
Abdelmalek Khorief Nacereddine ◽  
Abdelhafid Djerourou
Keyword(s):  
Activation Energy ◽  
Hydrogen Bond ◽  
Transition State ◽  
Molecular Mechanism ◽  
Theoretical Method ◽  
Noncovalent Interaction ◽  
Covalent Interaction ◽  
Energy Profiles ◽  
One Step ◽  
Step Mechanism

The selectivity and molecular mechanism of the intramolecular [3+2] cycloaddition (IMDC) reaction of nitrone-alkene generated from m-allyloxybenzaldehyde has been studied computationally using B3LYP/6-31G(d) theoretical method. The energy profiles indicate that this IMDC reaction favours kinetically the formation of the fused-endo, as observed experimentally. The solvent has no influence on the mechanism and selectivity, but it increases slightly the activation energy and decreases the exothermic character of this IMDC reaction. The analysis through electron localisation function (ELF) of the favourable fused-endo pathway shows that the formation of the C–O and C–C new bonds occurred via a non-concerted synchronous one-step mechanism. The analysis of noncovalent interaction using Non-covalent interaction (NCI) and QTAIM analyses of the structure of the fused-endo transition state indicates that the hydrogen-bond formed at this approach is the origin for the favouring of the fused-endo pathway.

Can the high reactivity of azomethine betaines in [3 + 2] cycloaddition reactions be explained using singlet-diradical character descriptors? What molecular mechanism is actually involved in these cycloadditions?

RSC Advances ◽  
2015 ◽  
Vol 5 (76) ◽  
pp. 62248-62259 ◽  
Author(s):  
Saeedreza Emamian ◽  
Tian Lu ◽  
Farid Moeinpour
Keyword(s):  
Molecular Mechanism ◽  
High Reactivity ◽  
Cycloaddition Reactions ◽  
Diradical Character ◽  
One Step ◽  
Step Mechanism

The singlet-diradical character of AZBs makes these TACs reactive in [3 + 2] cycloaddition toward ethylene taking place via a non-concerted one-step mechanism.

scholarly journals Insights Into The Origin of Selectivity For [2+2] Cycloaddition Step Reaction Involved In The Mechanism of Enantioselective Reduction of Ketones With Borane Catalyzed By A B-Methoxy Oxazaborolidine Catalyst Derived From (–)-β-Pinene. A DFT And Combined Topological ELF, NCI And QTAIM Study

2021 ◽  
Author(s):  
Hichem Sadrik Kettouche
Keyword(s):  
Density Functional ◽  
Topological Analysis ◽  
Density Functional Theory Method ◽  
Theoretical Studies ◽  
Functional Theory ◽  
Enantioselective Reduction ◽  
The Density Functional Theory ◽  
One Step ◽  
Step Mechanism ◽  
Reduction Of Ketones

Abstract Theoretical studies on [2+2] cycloaddition step involved in the Enantioselective Reduction of ketones with borane catalyzed by a B-MethoxyOxazaborolidine Catalyst Derived from Pinene has been performed by means of the Density Functional Theory method (DFT) at MPWB1K /6-31G (d,p). The formation of the M5a(S) complexes via transition state TSa(S) was the more favorable pathway among other [2+2]cycloaddition competing steps. The explanation of the formation of O-B and N-B through two-stage one-step mechanism was allowed by means of the electron localization function (ELF) topological analysis. NCI and QTAIM analysis of the two computed transition states TSa(S) and TSa(R) indicate that the difference between both in term of stability comes mainly from the orientation of the methanediyl group inside the pinene skeleton, which implies that CH-H…O interaction found at TSa(S) is the great factor that makes it more stable than TSa(R).

A molecular electron density theory study on the [3+2] cycloaddition reaction of thiocarbonyl ylides with hetaryl thioketones

2018 ◽  
Vol 42 (14) ◽  
pp. 11819-11830 ◽  
Author(s):  
Afsaneh Asr ◽  
Mehran Aghaie ◽  
Saeedreza Emamian ◽  
Hossein Aghaie
Keyword(s):  
Molecular Mechanism ◽  
Electron Density ◽  
Cycloaddition Reaction ◽  
Two Stage ◽  
Molecular Electron ◽  
One Step ◽  
Molecular Electron Density Theory

In situ generated TCY 2 is trapped with THK 3 over the course of a non-polar, entirely C1–C4 regioselective, pdr-type 32CA reaction passing through TS 1 in a non-concerted two-stage one-step molecular mechanism.

scholarly journals A Molecular Electron Density Theory Study of the Reactivity of Azomethine Imine in [3+2] Cycloaddition Reactions

2017 ◽  
Author(s):  
Luis R. Domingo ◽  
Mar Ríos-Gutiérrez
Keyword(s):  
Electron Density ◽  
Topological Analysis ◽  
Complete Agreement ◽  
Azomethine Imine ◽  
Molecular Electron ◽  
One Step ◽  
Molecular Electron Density Theory ◽  
Dft Reactivity Indices ◽  
Step Mechanism

The electronic structure and the participation of the simplest azomethine imine (AI) in [3+2] cycloaddition (32CA) reactions have been analysed within the Molecular Electron Density Theory (MEDT) using DFT calculations at the MPWB1K/6-311G(d) level. Electron localisation function (ELF) topological analysis reveals that AI has a pseudoradical structure, while the conceptual DFT reactivity indices characterise this TAC as a moderate electrophile and a good nucleophile. The non-polar 32CA reaction of AI with ethylene takes place through a one-step mechanism with low activation energy, 5.3 kcal/mol-1. A bonding evolution theory (BET) study indicates that this reaction takes place through a non-concerted [2n+2τ] mechanism in which the C–C bond formation is clearly anticipated prior to the C–N one. On the other hand, the polar 32CA reaction of AI with dicyanoethylene takes place through a two-stage one-step mechanism. Now, the more favourable regioisomeric transition state structure (TS) is located 8.5 kcal•mol−1 below the reagents, in complete agreement with the high polar character of the TS. The current MEDT study makes it possible to extend Domingo’s classification of 32CA reactions to a new pra-type of reactivity.

scholarly journals Unveiling the Intramolecular Ionic Diels-Alder Reactions within the Molecular Electron Density Theory

2021 ◽  
Author(s):  
Luis R. Domingo ◽  
Mar Ríos-Gutiérrez ◽  
María José Aurell
Keyword(s):  
Electron Density ◽  
Activation Enthalpy ◽  
Topological Analysis ◽  
Chair Conformation ◽  
Diels Alder ◽  
Molecular Electron ◽  
One Step ◽  
Molecular Electron Density Theory ◽  
Step Mechanism ◽  
Density Transfer

The intramolecular ionic Diel-Alder (IIDA) reactions of two dieniminiums have been studied within the Molecular Electron Density Theory (MEDT) at the B97XD/6-311G(d,p) computational level. ELF topological analysis of dieniminiums shows that its electronic structure can been seen as the sum of those of butadiene and ethaniminium. The superelectrophilic character of dieniminiums accounts for the high intramolecular global electron density transfer taking place between the diene and iminium frameworks at the transition state structures (TSs) of these IIDA reactions. The activation enthalpy associated to the IIDA reaction of the experimental dieniminium, 8.7 kcal·mol-1, is closer to that of the ionic Diels-Alder (I-DA) reaction between butadiene and ethaniminium, 9.3 kcal·mol-1. However, the activation Gibbs free energy of the IIDA reaction is 12.7 kcal·mol-1 lower than that of the intermolecular I-DA reaction. The strong exergonic character of the IIDA reaction, higher than 17 kcal·mol-1, makes the reaction irreversible. These IIDA reactions present a total re/exo and si/endo diastereoselectivity, which is controlled by the most favourable chair conformation of the tetramethylene chain. Electron localization function (ELF) topological analysis of the single bond formation indicates that these IIDA reactions take place through a non-concerted two-stage one-step mechanism. Finally, ELF and atoms-in-molecules (AIM) topological analyses of the TS associated to inter and intramolecular processes show the great similitude among them.

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