scholarly journals The Azide-Allene Dipolar Cycloaddition: Is DFT Able to Predict Site- and Regio-Selectivity?

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 928
Author(s):  
Giorgio Molteni ◽  
Alessandro Ponti
Keyword(s):  
Transition State ◽  
1H Nmr ◽  
Computational Scheme ◽  
Dipolar Cycloaddition ◽  
Experimental Site ◽  
Dipolar Cycloadditions ◽  
Reactivity Indices ◽  
One Step ◽  
Experimental Findings ◽  
Step Mechanism

The site- and regio-selectivity of thermal, uncatalysed 1,3-dipolar cycloadditions between arylazides and mono- or tetra-substituted allenes with different electronic features have been investigated by both conceptual (reactivity indices) and computational (M08-HX, ωB97X-D, and B3LYP) DFT approaches. Both approaches show that these cycloadditions follow a nonpolar one-step mechanism. The experimental site- and regio-selectivity of arylazides towards methoxycarbonyl- and sulfonyl-allenes as well as tetramethyl- and tetrafluoro-allenes was calculated by DFT transition state calculations, achieving semiquantitative agreement to both previous and novel experimental findings. From the mechanistic standpoint, 1H-NMR evidence of a methylene-1,2,3-triazoline intermediate reinforces the reliability of the computational scheme.

Mechanism and regioselectivity of 1,3-dipolar cycloaddition reactions of bicyclic monoterpenes with aryl and heteroaryl nitrile oxides: a DFT study

2015 ◽  
Vol 93 (7) ◽  
pp. 749-753 ◽  
Author(s):  
Hossein Eshghi ◽  
Amir Khojastehnezhad ◽  
Farid Moeinpour ◽  
Mehdi Bakavoli
Keyword(s):  
Gas Phase ◽  
Density Functional ◽  
Energy Surface ◽  
Dipolar Cycloaddition ◽  
Cycloaddition Reactions ◽  
Functional Theory ◽  
Nitrile Oxides ◽  
Reactivity Indices ◽  
One Step ◽  
Step Mechanism

The reactivity and regioselectivity of 1,3-dipolar cycloaddition reactions of aryl and heteroaryl nitrile oxides (1a–1c) with bicyclic monoterpenes (R)-(+)-a-pinene (2a) and (S)-(–)-b-pinene (2b) have been investigated by using density functional theory based on reactivity indices and activation energy calculations at the B3LYP/6-31G(d) level of theory in the gas phase. The potential energy surface analyses for both reactions are in agreement with the experimental observations. Moreover, our calculations on the geometries, bond orders, and global electron density transfers at the transition state structures shows that these 1,3- dipolar cycloaddition reactions occur via an asynchronous one-step mechanism.

scholarly journals The reaction mechanism of the [2+3] cycloaddition between α-phenylnitroethene and (Z)-C,N-diphenylnitrone in the light of a B3LYP/6-31G(d) computational study

2013 ◽  
Vol 11 (3) ◽  
pp. 404-412 ◽  
Author(s):  
Radomir Jasiński ◽  
Maria Mikulska ◽  
Andrzej Barański
Keyword(s):  
Reaction Mechanism ◽  
Gas Phase ◽  
Computational Study ◽  
Reaction Medium ◽  
Reaction Pathways ◽  
Reactivity Indices ◽  
Polar Media ◽  
One Step ◽  
Step Mechanism

AbstractAbstract The analysis of reactivity indices suggests the polar nature of the [2+3] cycloaddition of a-phenylnitroethene to (Z)-C,N-diphenylnitrone. Similar conclusions can be drawn from the investigation of the reaction pathways using the B3LYP/6-31g(d) algorithm. This shows that the cycloaddition mechanism depends on the polarity of the reaction medium. A one-step mechanism is followed in the gas phase and toluene in all the theoretically possible pathways. In more polar media (nitromethane, water), a zwitterionic, two-step rather than a one-step mechanism occurs in the pathway leading to 3,4-trans-2,3,5-triphenyl-4-nitroisoxazolidine. Graphical abstract

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.

scholarly journals A Density-Functional Study of the Conformational Preference of Acetylcholine in the Neutral Hydrolysis

Molecules ◽  
2020 ◽  
Vol 25 (3) ◽  
pp. 670 ◽  
Author(s):  
Rizka N. Fadilla ◽  
Febdian Rusydi ◽  
Nufida D. Aisyah ◽  
Vera Khoirunisa ◽  
Hermawan K. Dipojono ◽  
...  
Keyword(s):  
Transition State ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Experimental Results ◽  
Functional Study ◽  
Conformational Preference ◽  
Reaction Energy ◽  
Density Functional Study ◽  
One Step ◽  
Experimental Findings

Acetylcholine, which is associated with Alzheimer’s disease, is widely known to have conformers. The preference of each conformer to undergo neutral hydrolysis is yet to be considered. In this study, we employed density-functional calculations to build the conformers and investigated their preference in one-step neutral hydrolysis. The results showed the preference in ten possible hydrolysis pathways involving seven acetylcholine conformers (reactant), four transition state structures, and two choline conformers (product). Three out of the seven acetylcholine conformers predicted from the results confirmed experimental findings on the conformers stability. We suggested that two out of ten possible pathways were observed in the experimental results based on agreement in reaction energy. Eventually, this study will emphasize the importance of considering acetylcholine conformers in its hydrolysis study.

scholarly journals Understanding the mechanism of the 1,3-dipolar cycloaddition reaction between a thioformaldehyde S-oxide and cyclobutadiene: Competition between the stepwise and concerted routes

2019 ◽  
Vol 44 (3) ◽  
pp. 213-221
Author(s):  
Bita Mohtat ◽  
Seyyed Amir Siadati ◽  
Mohammad A Khalilzadeh
Keyword(s):  
Transition State ◽  
Cycloaddition Reaction ◽  
Dipolar Cycloaddition ◽  
Theoretical Methods ◽  
One Step

Changing the mechanism of the widely used 1,3-dipolar cycloaddition reaction from its usual asynchronous one-step pattern to the rarely observed stepwise form leads to the emergence of intermediates, side products, and other impurities. Thus, it is crucial to determine the nature of the mechanism of the 1,3-dipolar cycloaddition reaction between a special 1,3-dipole and a specified dipolarophile (by theoretical methods) before using them for synthesizing a desired product. In this study, therefore, we have investigated the possibility of some probable intermediates emergence in the 1,3-dipolar cycloaddition reaction between cyclobutadiene and thioformaldehyde S-oxide. The results showed that emergence of Int (B) (−52.1 kcal mol−1) via transition state (B-1) is favorable both thermodynamically and kinetically (in comparison with all other stepwise routes). That is, developing probable impurities should not be neglected at least in the cases of the reactions between some thioformaldehyde S-oxide and some dipolarophiles.

1,3-Dipolar cycloadditions of Arylcarbonitrile Oxides and Diaryl Nitrilimines with Some 2-Arylmethylene-1,3-Indanediones; regiochemistry of the Reactions

2003 ◽  
Vol 2003 (4) ◽  
pp. 204-207 ◽  
Author(s):  
Sarra Boudriga ◽  
Mohiedinne Askri ◽  
Rafik Gharbi ◽  
Mohamed Rammah ◽  
Kabula Ciamala
Keyword(s):  
Ring Closure ◽  
Dipolar Cycloaddition ◽  
Dipolar Cycloadditions

Ring-closure reaction affording spiroisoxazolines and spiropyrazolines via a 1,3-dipolar cycloaddition between the title compounds, occurs with high regioselectivity.

scholarly journals Application of β-Phosphorylated Nitroethenes in [3+2] Cycloaddition Reactions Involving Benzonitrile N-Oxide in the Light of a DFT Computational Study

Organics ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 26-37
Author(s):  
Karolina Zawadzińska ◽  
Karolina Kula
Keyword(s):  
Density Functional ◽  
Reaction Path ◽  
Computational Study ◽  
Cyano Group ◽  
Cycloaddition Reactions ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Reaction Channels ◽  
One Step ◽  
Step Mechanism

The regiochemistry of [3+2] cycloaddition (32CA) processes between benzonitrile N-oxide 1 and β-phosphorylated analogues of nitroethenes 2a–c has been studied using the Density Functional Theory (DFT) at the M062X/6-31+G(d) theory level. The obtained results of reactivity indices show that benzonitrile N-oxide 1 can be classified both as a moderate electrophile and moderate nucleophile, while β-phosphorylated analogues of nitroethenes 2a–c can be classified as strong electrophiles and marginal nucleophiles. Moreover, the analysis of CDFT shows that for [3+2] cycloadditions with the participation of β-phosphorylatednitroethene 2a and β-phosphorylated α-cyanonitroethene 2b, the more favored reaction path forms 4-nitro-substituted Δ2-isoxazolines 3a–b, while for a reaction with β-phosphorylated β-cyanonitroethene 2c, the more favored path forms 5-nitro-substituted Δ2-isoxazoline 4c. This is due to the presence of a cyano group in the alkene. The CDFT study correlates well with the analysis of the kinetic description of the considered reaction channels. Moreover, DFT calculations have proven the clearly polar nature of all analyzed [3+2] cycloaddition reactions according to the polar one-step mechanism.

Regioselection in 1,3-Dipolar Cycloadditions of 3-Methylpyridine N-Imide to Aromatic Carbonitriles. Synthesis of 2-Aryl-8-Methyl[1,2,4]Triazolo [1,5-a]Pyridines

2002 ◽  
Vol 2002 (11) ◽  
pp. 560-561 ◽  
Author(s):  
Zhang Guolin ◽  
Hu Yongzhou
Keyword(s):  
Potassium Hydroxide ◽  
Dipolar Cycloaddition ◽  
Aromatic Nitriles ◽  
Dipolar Cycloadditions

1-Amino-3-methylpyridinium mesitylenesulfonate (3) reacts with aromatic nitriles in the presence of potassium hydroxide, undergoing 1,3-dipolar cycloaddition followed by elimination of H2 to give 2-aryl-8-methyl[1,2,4]triazolo[1,5- a]pyridines as the major products, rather than the 6-methyl isomers.

scholarly journals Quinazolin-4(3H)-ones and 5,6-Dihydropyrimidin-4(3H)-ones from β-Aminoamides and Orthoesters

Molecules ◽  
2018 ◽  
Vol 23 (11) ◽  
pp. 2925 ◽  
Author(s):  
Joshua Gavin ◽  
Joel Annor-Gyamfi ◽  
Richard Bunce
Keyword(s):  
Acetic Acid ◽  
Melting Point ◽  
1H Nmr ◽  
13C Nmr ◽  
Pressure Tube ◽  
Absolute Ethanol ◽  
Basic Nitrogen ◽  
One Step ◽  
Ft Ir

Quinazolin-4(3H)-ones have been prepared in one step from 2-aminobenzamides and orthoesters in the presence of acetic acid. Simple 2-aminobenzamides were easily converted to the heterocycles by refluxing in absolute ethanol with 1.5 equivalents of the orthoester and 2 equivalents of acetic acid for 12–24 h. Ring-substituted and hindered 2-aminobenzamides as well as cases incorporating an additional basic nitrogen required pressure tube conditions with 3 equivalents each of the orthoester and acetic acid in ethanol at 110 °C for 12–72 h. The reaction was tolerant towards functionality on the benzamide and a range of structures was accessible. Workup involved removal of the solvent under vacuum and either recrystallization from ethanol or trituration with ether-pentane. Several 5,6-dihydropyrimidin-4(3H)-ones were also prepared from 3-amino-2,2-dimethylpropionamide. All products were characterized by melting point, FT-IR, 1H-NMR, 13C-NMR, and HRMS.

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