One-step mechanism of hydrogen transfer in "amine – triplet nitro compound" system

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.

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Unveiling the Unexpected Reactivity of Electrophilic Diazoalkanes in [3+2] Cycloaddition Reactions within Molecular Electron Density Theory

10.20944/preprints202012.0364.v1 ◽

2020 ◽

Author(s):

Luis R. Domingo ◽

Mar Ríos-Gutiérrez ◽

Nivedita Acharjee

Keyword(s):

Electron Density ◽

Complete Agreement ◽

Slowing Down ◽

Molecular Electron ◽

One Step ◽

Molecular Electron Density Theory ◽

Electrophilic Character ◽

Step Mechanism ◽

Computational Level ◽

Density Transfer

The [3+2] cycloaddition (32CA) reactions of strongly nucleophilic norbornadiene (NBD) with simplest diazoalkane (DAA) and three DAAs of increased electrophilicity have been studied within the Molecular Electron Density Theory (MEDT) at the MPWB1K/6-311G(d,p) computational level. These pmr-type 32CA reactions follow an asynchronous one-step mechanism with activation enthalpies ranging from 17.7 to 27.9 kcal·mol-1 in acetonitrile. The high exergonic character of these reactions makes them irreversible. The presence of electron-withdrawing (EW) substituents in the DAA increases the activation enthalpies, in complete agreement with the experimental slowing-down of the reactions, but contrary to the Conceptual DFT prediction. Despite the nucleophilic and electrophilic character of the reagents, the global electron density transfer at the TSs indicates rather non-polar 32CA reactions. The present MEDT study allows establishing that the depopulation of the NNC core in this series of DAAs with the increase of the EW character of the substituents present at the carbon center is responsible for the experimentally found deceleration.

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Invited Review. A Combinatorial Approach to the Development of Environmentally Benign Organic Chemical Preparations

Australian Journal of Chemistry ◽

10.1071/c98156 ◽

1999 ◽

Vol 52 (2) ◽

pp. 83 ◽

Cited By ~ 101

Author(s):

Christopher R. Strauss

Keyword(s):

Hydrogen Transfer ◽

Aldol Condensation ◽

Aqueous Media ◽

Environmentally Benign ◽

Organic Chemical ◽

Coupling Reactions ◽

Heck Coupling ◽

Solvent Free Conditions ◽

Microwave Reactors ◽

One Step

Enabling technologies and methodologies were established and combined to afford various environmentally benign processes for laboratory-scale organic synthesis and for the production of fine chemicals, intermediates and pharmaceuticals. The technologies comprised continuous and batch microwave reactors and catalytic membranes. The methodologies included solvent-free conditions, catalysed or uncatalysed processes, the use of aqueous media at high temperature and non-extractive techniques for product isolation. Applications included Hofmann eliminations, Willgerodt and Jacobs–Gould reactions, indole transformations, aldol condensation, Rupe and Meyer–Schuster rearrangements and C–C coupling reactions (including a tandem Heck coupling–dehydrogenation). New processes for catalytic etherification, uncatalysed hydrogen transfer and a one-step arylamidation were also developed. Typical products were N-(4-hydroxyphenyl)acetamide, carvacrol, a-phenylacetamide, cinnamaldehyde, cinnamyl alcohol, acetophenone, indole, 3-hydroxy-1,2-dimethyl-4-pyridone, di(2-phenylethyl) ether, di(cyclopropylmethyl) ether, 3-methylcyclopent-2-enone and a synthetic precursor of nalidixic acid.

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Understanding the Reactivity of Trimethylsilyldiazoalkanes Participating in [3+2] Cycloaddition Reactions towards Diethylfumarate with a Molecular Electron Density Theory Perspective

Organics ◽

10.3390/org1010002 ◽

2020 ◽

Vol 1 (1) ◽

pp. 3-18

Author(s):

Luis R. Domingo ◽

Nivedita Acharjee ◽

Haydar A. Mohammad-Salim

Keyword(s):

Electron Density ◽

Energy Cost ◽

Trimethylsilyl Group ◽

Gibbs Energies ◽

Molecular Electron ◽

One Step ◽

Molecular Electron Density Theory ◽

Non Covalent Interactions ◽

Covalent Interactions ◽

Step Mechanism

A Molecular Electron Density Theory (MEDT) study is presented here for [3+2] cycloaddition (32CA) reactions of three trimethylsilyldiazoalkanes with diethyl fumarate. The presence of silicon bonded to the carbon of these silyldiazoalkanes changes its structure and reactivity from a pseudomonoradical to that of a zwitterionic one. A one-step mechanism is predicted for these polar zw-type 32CA reactions with activation enthalpies in CCl4 between 8.0 and 19.7 kcal·mol−1 at the MPWB1K (PCM)/6-311G(d,p) level of theory. The negative reaction Gibbs energies between −3.1 and −13.2 kcal·mole−1 in CCl4 suggests exergonic character, making the reactions irreversible. Analysis of the sequential changes in the bonding pattern along the reaction paths characterizes these zw-type 32CA reactions. The increase in nucleophilic character of the trimethylsilyldiazoalkanes makes these 32CA reactions more polar. Consequently, the activation enthalpies are decreased and the TSs require less energy cost. Non-covalent interactions at the TSs account for the stereoselectivity found in these 32CA reactions involving the bulky trimethylsilyl group.

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Thermal decomposition of ammonium hexachloroosmate

Physical Chemistry Chemical Physics ◽

10.1039/c6cp07133c ◽

2016 ◽

Vol 18 (48) ◽

pp. 33134-33141 ◽

Cited By ~ 5

Author(s):

T. I. Asanova ◽

I. Kantor ◽

I. P. Asanov ◽

S. V. Korenev ◽

K. V. Yusenko

Keyword(s):

Thermal Decomposition ◽

Time Resolved ◽

One Step ◽

Step Mechanism

A one-step mechanism of the thermal decomposition of (NH4)2[OsCl6] suggested previously proves to be unworkable under a time-resolved ED XAFS and PXRD study.

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Serine peptidase catalytic machinery: Cooperative one-step mechanism

International Journal of Quantum Chemistry ◽

10.1002/(sici)1097-461x(1999)73:2<161::aid-qua10>3.0.co;2-e ◽

1999 ◽

Vol 73 (2) ◽

pp. 161-174 ◽

Cited By ~ 14

Author(s):

G. Dive ◽

D. Dehareng

Keyword(s):

Serine Peptidase ◽

One Step ◽

Step Mechanism

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

Canadian Journal of Chemistry ◽

10.1139/cjc-2014-0551 ◽

2015 ◽

Vol 93 (7) ◽

pp. 749-753 ◽

Cited By ~ 5

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.

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