Reactions of an Aluminium(I) Reagent with 1,2-, 1,3- and 1,5-Dienes: Dearomatisation, Reversibility, and a Pericyclic Mechanism

2019 ◽  
Author(s):  
Clare Bakewell ◽  
Martí Garçon ◽  
Richard Y Kong ◽  
Louisa O'Hare ◽  
Andrew J. P. White ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Dft Calculations ◽  
Transition State ◽  
Reaction Pathways ◽  
Aromatic Rings ◽  
Aromatic Character ◽  
Pericyclic Reaction

The reactions of an aluminium(I) reagent with a series of 1,2-, 1,3- and 1,5-dienes are reported. In the case of 1,3-dienes the reaction occurs by a pericyclic reaction mechanism, specifically a cheletropic cycloaddition, to form aluminocyclopentene containing products. This mechanism has been interrogated by stereochemical experiments and DFT calculations. The stereochemical experiments show that the (4+1) cycloaddition follows a suprafacial topology, while calculations support a concerted albeit asynchronous pathway in which the transition state demonstrates aromatic character. Remarkably, the substrate scope of the (4+1) cycloaddition includes dienes that are either in part, or entirely, contained within aromatic rings. In these cases, reactions occur with dearomatisation of the substrate and can be reversible. In the case of 1,2- or 1,5-dienes complementary reactivity is observed; the orthogonal nature of the C=C π-bonds (1,2-diene) and the homoconjugated system (1,5-diene) both disfavour a (4+1) cycloaddition. Rather, reaction pathways are determined by an initial (2+1) cycloaddition to form an aluminocyclopropane intermediate which can in turn undergo insertion of a further C=C π-bond leading to complex organometallic products that incorporate fused hydrocarbon rings.

Reactions of an Aluminium(I) Reagent with 1,2-, 1,3- and 1,5-Dienes: Dearomatisation, Reversibility, and a Pericyclic Mechanism

2019 ◽  
Author(s):  
Clare Bakewell ◽  
Martí Garçon ◽  
Richard Y Kong ◽  
Louisa O'Hare ◽  
Andrew J. P. White ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Dft Calculations ◽  
Transition State ◽  
Reaction Pathways ◽  
Aromatic Rings ◽  
Aromatic Character ◽  
Pericyclic Reaction

The reactions of an aluminium(I) reagent with a series of 1,2-, 1,3- and 1,5-dienes are reported. In the case of 1,3-dienes the reaction occurs by a pericyclic reaction mechanism, specifically a cheletropic cycloaddition, to form aluminocyclopentene containing products. This mechanism has been interrogated by stereochemical experiments and DFT calculations. The stereochemical experiments show that the (4+1) cycloaddition follows a suprafacial topology, while calculations support a concerted albeit asynchronous pathway in which the transition state demonstrates aromatic character. Remarkably, the substrate scope of the (4+1) cycloaddition includes dienes that are either in part, or entirely, contained within aromatic rings. In these cases, reactions occur with dearomatisation of the substrate and can be reversible. In the case of 1,2- or 1,5-dienes complementary reactivity is observed; the orthogonal nature of the C=C π-bonds (1,2-diene) and the homoconjugated system (1,5-diene) both disfavour a (4+1) cycloaddition. Rather, reaction pathways are determined by an initial (2+1) cycloaddition to form an aluminocyclopropane intermediate which can in turn undergo insertion of a further C=C π-bond leading to complex organometallic products that incorporate fused hydrocarbon rings.

scholarly journals Theoretical study on pegylation reaction mechanisms of IFN-α-2a, IFN-α-2b and IFN-β-1a

2017 ◽  
Vol 82 (7-8) ◽  
pp. 841-850
Author(s):  
Mohammad Taqavian ◽  
Daryoush Abedi ◽  
Fatemeh Zigheimat ◽  
Leila Zeidabadinejad
Keyword(s):  
Polyethylene Glycol ◽  
Reaction Mechanism ◽  
Dft Calculations ◽  
Transition State ◽  
Reaction Mechanisms ◽  
Theoretical Study ◽  
Computational Study ◽  
Single Transition ◽  
Experimental Works ◽  
Ab Initio And Dft

Ab initio and DFT calculations have been carried out to study the reaction mechanism between interferons (IFNs) ?-2a, ?-2b and ?-1a and polyethylene glycol (PEG) group. The calculations show that the mechanisms are concerted, in agreement with the results of experimental works. However, although it appears that there is one single transition state, the characteristics of its structure reveal a very synchronous reaction mechanism. The reactions are clearly exothermic and as well have feasible activation energies. Our computational study shows that the lowest transition state energies are related to Lys 134, His 34 and Met 1 of IFN-?-2a, IFN-?-2b and IFN-?-1a, respectively.

Unraveling the Mechanism of Tricyclic Bis-spiroketal Formation from Diyne Diol by DFT Study

2019 ◽  
Vol 16 (5) ◽  
pp. 392-395
Author(s):  
Kamlesh Sharma
Keyword(s):  
Density Functional Theory ◽  
Reaction Mechanism ◽  
Dft Calculations ◽  
Density Functional ◽  
Activation Parameters ◽  
Product Formation ◽  
Ring Closure ◽  
Reaction Pathways ◽  
Enol Ether ◽  
Functional Theory

The mechanism of addition of nucleophiles to the π-acid complexed alkynes has been studied successfully by the assessment of energy of intermediates and activation parameters. To elucidate the origin of stereoselectivity and predict the reaction pathways, the geometry optimizations of reactants, products, intermediates and transition states, were calculated by using density functional theory (DFT) at the B3LYP/6-31+G(d) method. The reaction mechanism of hydration of alkynes in the catalyzed synthesis of bis-spiroketal by DFT calculations is explored. The pyranyl enol ether was formed regioselectively by the first ring closure. Further, bis-enol ether was formed by second 6-exodig addition. Then, dehydration, followed by dehydrative ring closure finally gave bis-spiroketal product. It is concluded that one of the most feasible reaction pathways comprises pyranyl enol ether and bis-enol ether formation as intermediates. The final cyclization step of product formation is endothermic. In terms of stereochemistry, the trans-product is found to be energetically more stable than cisproduct and hence supports the electivity of the reaction.

scholarly journals Quantum chemical study of reaction mechanism between plutonium and Nitrogen

2021 ◽  
Author(s):  
Zhao-Yang Zhao ◽  
Guo-Liang Wang ◽  
Xu-Dan Chen ◽  
Chun-Bao Qi ◽  
Xin-Li Sun
Keyword(s):  
Reaction Mechanism ◽  
Potential Energy ◽  
Transition State ◽  
Density Functional ◽  
Transition States ◽  
Reaction Pathways ◽  
Stationary Points ◽  
Main Reaction ◽  
Intrinsic Reaction Coordinate ◽  
Phase Reaction

Abstract The study of the reaction between plutonium and nitrogen is helpful to further understand the interaction between plutonium and air gas molecules. For the nitridation reaction of plutonium, there is no report on the microscopic reaction mechanism of this system at present. Therefore, the microcospic mechanism of gas phase reaction of Pu with N 2 is studied in this paper based on the density functional theory (DFT) using different functions. In this paper, the geometry of stationary points on the potential energy surface is optimized. In addition, the transition states are verified by the frequency analysis method and the intrinsic reaction coordinate (IRC) method. Finally, we obtain the reaction potential energy curve and the micro reaction pathways. The analysis of reaction mechanism shows that the reaction of Pu with N 2 has two pathways. The pathway-1 (Pu+N 2 →R1→TS1→PuN 2 ) has a T-shaped transition state and the pathway-2 (Pu+N 2 →R 2 →TS 2 →PuN+N) has a L-shaped transition state. Moreover, both transition states have only one virtual frequency. The energy analysis shows that pathway-1 is the main reaction pathway. The nature of the Pu-N bonding evolution along the pathways is studied by atoms in molecules (AIM) and electron localization function (ELF) topological approaches. In order to analyse the role of 5f orbital of plutonium atom in the reaction, the variation of density of state along the pathways is performed. The results show that the 5f orbital makes major contributions to the formation of Pu-N bonds. Meanwhile, the influence of different temperatures on the reaction rate is revealed by calculating the rate constants of the two reaction pathways.

scholarly journals Catalytic mechanism of the colistin resistance protein MCR-1

2021 ◽  
Author(s):  
Reynier Suardíaz ◽  
Emily Lythell ◽  
Philip Hinchliffe ◽  
Marc van der Kamp ◽  
James Spencer ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Antimicrobial Resistance ◽  
Dft Calculations ◽  
Catalytic Reaction ◽  
Catalytic Mechanism ◽  
Cluster Models ◽  
Colistin Resistance ◽  
Resistance Protein ◽  
Catalytic Reaction Mechanism

Elucidation of the catalytic reaction mechanism of MCR-1 enzyme, responsible for the antimicrobial resistance to colistin, using DFT calculations on cluster models.

Reaction mechanism studies. 5. The mechanism of the diaxial → diequatorial rearrangement of β-chlorothioethers

1968 ◽  
Vol 46 (1) ◽  
pp. 9-13 ◽  
Author(s):  
J. F. King ◽  
K. Abikar
Keyword(s):  
Reaction Mechanism ◽  
Transition State ◽  
Nitro Group ◽  
Ion Pair ◽  
Concerted Mechanism

p-Methoxy- and p-nitro substituted analogues (1b and 1c) of the diaxial β-chlorothioether 2β-chloro-3α-(phenylthio)-5α-cholestane (1a), have been prepared and found to undergo the diaxial → diequatorial rearrangement. The rates of rearrangement of these compounds show the sequence p-methoxy > H > p-nitro. It is concluded that the transition state for the rearrangement is polarized in the sense of a sulfonium chloride (3). The rearrangement of 1a is 1600 times faster in butanol than in decalin (at 110°). There is thus no inherent insensitivity to solvent change in a rearrangement in which there may be a "four-atom arrangement" in the transition state, a conclusion relevant to previous work on the diaxial → diequatorial rearrangement of 1,2-dibromides (1). It was further found that the nitro group slowed the rearrangement (at 110°) more in butanol than in decalin, an observation regarded as consistent with, but not requiring, the incursion of a merged ion-pair, cyclic concerted mechanism.

scholarly journals More and Faster: Simultaneously Improving Reaction Coverage and Computational Cost in Automated Reaction Prediction Tasks

2020 ◽  
Author(s):  
Qiyuan Zhao ◽  
Brett Savoie
Keyword(s):  
Transition State ◽  
Domain Knowledge ◽  
Low Cost ◽  
Computational Cost ◽  
Chemical Degradation ◽  
Reaction Pathways ◽  
Reaction Networks ◽  
Complex Reaction ◽  
Success Rates ◽  
Reaction Prediction

<div> <div> <div> <p>Automated reaction prediction has the potential to elucidate complex reaction networks for applications ranging from combustion to materials degradation. Although substantial progress has been made in predicting specific reaction pathways and resolving mechanisms, the computational cost and inconsistent reaction coverage of automated prediction are still obstacles to exploring deep reaction networks without using heuristics. Here we show that cost can be reduced and reaction coverage can be increased simultaneously by relatively straight- forward modifications of the reaction enumeration, geometry initialization, and transition state convergence algorithms that are common to many emerging prediction methodologies. These changes are implemented in the context of Yet Another Reaction Program (YARP), our reaction prediction package, for which we report a head-to-head comparison with prevailing methods for two benchmark reaction prediction tasks. In all cases, we observe near perfect recapitulation of established reaction pathways and products by YARP, without the use of heuristics or other domain knowledge to guide reaction selection. In addition, YARP also discovers many new kinetically relevant pathways and products reported here for the first time. This is achieved while simultaneously reducing the cost of reaction characterization nearly 100-fold and increasing transition state success rates and intended rates over 2-fold and 10-fold, respectively, compared with recent benchmarks. This combination of ultra-low cost and high reaction-coverage creates opportunities to explore the reactivity of larger sys- tems and more complex reaction networks for applications like chemical degradation, where approaches based on domain heuristics fail. </p> </div> </div> </div>

scholarly journals Unprecedented η3-Coordination and Functionalization of the 2-Phosphaethynthiolate Anion at Lanthanum(III)

2021 ◽  
Author(s):  
Fabian A. Watt ◽  
Lukas Burkhardt ◽  
Roland Schoch ◽  
Stefan Mitzinger ◽  
Matthias Bauer ◽  
...  
Keyword(s):  
Reaction Mechanism ◽  
Dft Calculations ◽  
Coordination Mode ◽  
Quantum Mechanical ◽  
Structural Comparison ◽  
Anion Complex ◽  
Steric Factors ◽  
Group 15 ◽  
Detailed Reaction Mechanism ◽  
The Ideal

We present the unprecedented <i>η</i>3-coordination of the 2-phosphaethynthiolate anion in the complex (PN)<sub>2</sub>La(SCP) (<b>2</b>) [PN = N-(2-(diisopropylphosphanyl)-4-methylphenyl)-2,4,6-trimethylanilide)]. Structural comparison with dinuclear thiocyanate bridged (PN)<sub>2</sub>La(<i>μ</i>-1,3-SCN)<sub>2</sub>La(PN)<sub>2</sub> (<b>3</b>) and azide bridged (PN)<sub>2</sub>La(<i>μ</i>-1,3-N3)<sub>2</sub>La(PN)<sub>2</sub> (<b>4</b>) complexes indicates that the [SCP]<sup>–</sup> coordination mode is mainly governed by electronic, rather than steric factors. Quantum mechanical investigations reveal large contributions of the antibonding π-orbital of the [SCP]<sup>–</sup> ligand to the LUMO of complex <b>2</b>, rendering it the ideal precursor for the first functionalization of the [SCP]<sup>–</sup> anion. Complex <b>2</b> was therefore reacted with CAACs which induced a selective rearrangement of the [SCP]<sup>–</sup> ligand to form the first CAAC stabilized group 15 – group 16 fulminate-type complexes (PN)<sub>2</sub>La{SPC(<sup>R</sup>CAAC)} (<b>5a,b</b>) (R = Ad, Me). A detailed reaction mechanism for the SCP to SPC isomerization is proposed based on DFT calculations.

The reactivity of stoichiometric tungsten oxide clusters towards carbon monoxide: the effects of cluster sizes and charge states

2015 ◽  
Vol 17 (17) ◽  
pp. 11499-11508 ◽  
Author(s):  
Shu-Juan Lin ◽  
Jing Cheng ◽  
Chang-Fu Zhang ◽  
Bin Wang ◽  
Yong-Fan Zhang ◽  
...  
Keyword(s):  
Carbon Monoxide ◽  
Reaction Mechanism ◽  
Dft Calculations ◽  
Tungsten Oxide ◽  
Charge States

DFT calculations were carried out to study the reaction mechanism for tungsten oxide clusters with CO.

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