Transition-state geometries and intrinsic reaction pathways for a series of formyl and thioformyl compounds

1992 ◽  
Vol 96 (4) ◽  
pp. 1691-1696 ◽  
Author(s):  
James Tyrrell ◽  
Wyn Lewis-Bevan
Keyword(s):  
Transition State ◽  
Reaction Pathways

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 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>

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 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>

Bifurcated dissociative photoionization mechanism of acetic acid anhydride revealed by imaging photoelectron photoion coincidence spectroscopy

2016 ◽  
Vol 18 (36) ◽  
pp. 25161-25168 ◽  
Author(s):  
Krisztina Voronova ◽  
Chrissa M. Mozaffari Easter ◽  
Krisztián G. Torma ◽  
Andras Bodi ◽  
Patrick Hemberger ◽  
...  
Keyword(s):  
Acetic Acid ◽  
Transition State ◽  
Acid Anhydride ◽  
Reaction Pathways ◽  
Dissociative Photoionization ◽  
Coincidence Spectroscopy

PEPICO allows us a peek beyond the transition state to identify bifurcated reaction pathways.

Biasing a transition state search to locate multiple reaction pathways

2003 ◽  
Vol 118 (21) ◽  
pp. 9533-9541 ◽  
Author(s):  
Baron Peters ◽  
WanZhen Liang ◽  
Alexis T. Bell ◽  
Arup Chakraborty
Keyword(s):  
Transition State ◽  
Reaction Pathways ◽  
Transition State Search

scholarly journals A CASSCF/CSAPT2 Study on the Reaction Pathways From HOSS to HSSO Radicals

2020 ◽  
Vol 165 ◽  
pp. 05025
Author(s):  
Haifeng Zhang ◽  
Jiubo Cui ◽  
Weiwei Pei ◽  
Dongfang Wang
Keyword(s):  
Transition State ◽  
High Energy ◽  
Oscillator Strengths ◽  
Reaction Pathways ◽  
Dihedral Angles ◽  
Geometrical Parameters ◽  
Excitation Energies ◽  
High Energy Barrier ◽  
Significant Difference ◽  
Total Energies

In this paper, we used the CASSCF/CASPT2 method to study the low-lying electronic states of the HOSS and HSSO radicals. Based on the Cs and C1 symmetries, the geometrical parameters, total energies, configurations, oscillator strengths, excitation energies, oscillator strengths and harmonic vibrational frequencies of the HOSS and HSSO radicals were calculated. We found that the ground state of HSSO radical with C1 symmetry has multi-configurational character, which leads to a significant difference of dihedral angles of HSSO radical among at our work and at References. Moreover, a transition state was given out in the pathway for the reaction from HOSS to HSSO. This transition state produces relatively high-energy barrier of 30.5 Kcal/mol corresponding to the gradual changes of the S2-H-O angle.

Pericyclic Reactions in the Syntheses of Densely Functionalized Heterocylces

2018 ◽  
Vol 15 (4) ◽  
pp. 438-486 ◽  
Author(s):  
Rabia Qamar ◽  
Aamer Saeed
Keyword(s):  
Transition State ◽  
Driving Force ◽  
High Efficiency ◽  
Reaction Pathways ◽  
Pericyclic Reactions ◽  
Cyclic Transition ◽  
Cyclic Transition State ◽  
Molecular Complexity ◽  
Nitrogen Ring

Background: Pericyclic reactions characterized by a cyclic transition state, have been established as a dominant approach for the synthesis of heterocyclic scaffolds owing to their tremendous efficacy, regioselectivity, and enantioselectivity. Pericyclic chemistry is a promising and creative route to various biologically significant five and six membered oxygen or nitrogen ring systems. Recognizing the reaction's potential, synthetic organic chemists have invested significant efforts in developing and applying a seemingly endless array of useful variations of pericyclic reactions. Objective: The driving force of this review is to focus the character of perfection and beauty inherent in these powerful reaction pathways that lead to unique and densely functionalized heterocylic assemblies. Conclusion: In this review, we have presented recent strategic applications of pericyclic reactions that provide quick access to molecular complexity with high efficiency. A summary of these illustrative examples will showcase the extensive role of pericyclic chemistry in the construction of synthetically intimidating structural motifs.

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