scholarly journals Valence tautomerism and recyclisation of type B mesoionic tetrazoles: a computational study

2021 ◽  
Author(s):  
Wojciech Piotr Oziminski ◽  
Christopher Antony Ramsden
Keyword(s):  
Solvent Effect ◽  
Ring Opening ◽  
Continuum Model ◽  
Computational Study ◽  
Reaction Pathway ◽  
Type B ◽  
Valence Tautomerism ◽  
Energy Profiles ◽  
Aqueous Solvation ◽  
Influence Of Solvent

AbstractThe energy profiles for ring opening of representative type B mesoionic 2,3-diphenyl-1,2,3,4-tetrazolium-5-olates, -thiolates, -aminides and –methylides and for alternative recyclisation pathways are investigated using ab initio MP2 calculations. The energetics of initial ring opening are found to be comparable for all systems, but the tetrazolium-5-olates are anomalous in that no alternative reaction pathway is accessible. The influence of solvent is explored using the polarised continuum model (PCM) method to simulate aqueous solvation. The only significant solvent effect is found to be solvation of the mesoionic precursors. This solvent effect correlates with dipole moment and disfavours initial valence tautomerism both kinetically and thermodynamically.

On the conformational structure of nicotinamide and methyl-1,4-dihydronicotinamide

1979 ◽  
Vol 44 (9) ◽  
pp. 2633-2638 ◽  
Author(s):  
Hans-Jörg Hofmann ◽  
Josef Kuthan
Keyword(s):  
Molecular Structure ◽  
Continuum Model ◽  
Model Analysis ◽  
Wave Functions ◽  
Conformational Structure ◽  
Influence Of Solvent

The conformation of nicotinamide (I) and 1-methyl-1,4-dihydronicotinamide (II) was examined using the NDDO method. The influence of solvent on the molecular structure of the title compounds was estimated by means of a continuum model. Analysis of the NDDO wave functions contributes to the knowledge about the mechanism of the NADH reduction.

Influence of solvent effect on polymorphism of 4-hydroxy-2-methyl-N-2-pyridyl-2H-1,2-benzothiazine-3-carboxamide-1, 1-dioxide (piroxicam)

1991 ◽  
Vol 21 (4) ◽  
pp. 519-522 ◽  
Author(s):  
M. Janik ◽  
Z. Malarski ◽  
J. Mrozińiski ◽  
J. Wajcht ◽  
Z. Zborucki
Keyword(s):  
Solvent Effect ◽  
Influence Of Solvent

scholarly journals Improving Solvation Energy Predictions Using The SMD Solvation Method and Semiempirical Electronic Structure Methods

2018 ◽  
Author(s):  
Jimmy C. Kromann ◽  
Casper Steinmann ◽  
Jan Halborg Jensen
Keyword(s):  
Continuum Model ◽  
Solvation Energy ◽  
Solvation Model ◽  
Polar Solvents ◽  
Data Set ◽  
Solvation Energies ◽  
Polarized Continuum Model ◽  
Electronic Structure Methods ◽  
Aqueous Solvation ◽  
Model C

The PM6 implementation in the GAMESS program is extended to elements requiring d-integrals and interfaced with the conducter-like polarized continuum model (C-PCM) of solvation, in- cluding gradients. The accuracy of aqueous solvation energies computed using AM1, PM3, PM6, and DFTB and the SMD continuum solvation model is tested using the MNSOL data set. The errors in SMD solvation energies predicted using NDDO-based methods is considerably larger than when using DFT and HF, with RMSE values of 3.4-5.9 (neutrals) and 6-15 kcal/mol (ions) compared to 2.4 and ca 5 kcal/mol for HF/6-31G(d). For the NDDO-based methods the errors are especially large for cations and considerably higher than the corresponding COSMO results, which suggests that the NDDO/SMD results can be improved by re-parameterizing the SMD parameters focusing on ions. We found the best results are obtained by changing only the radii for hydrogen, carbon, oxygen, nitrogen, and sulfur and this leads to RMSE values for PM3 (neutrals: 2.8/ions: ca 5 kcal/mol), PM6 (4.7/ca 5 kcal/mol), and DFTB (3.9/ca 5 kcal/mol) that are more comparable to HF/6-31G(d) (2.4/ca 5 kcal/mol). Though the radii are optimized to reproduce aqueous solvation energies, they also lead more accurate predictions for other polar solvents such as DMSO, acetonitrile, and methanol, while the improvements for non-polar solvents are negligible.

Synthesis of novel N-functionalized 4-aryl-tetrahydrobiquinoline-2,5-(1H,3H)-diones via one-pot three-component reaction: a joint experimental and computational study

2018 ◽  
Vol 96 (12) ◽  
pp. 1071-1078
Author(s):  
Vahideh Zadsirjan ◽  
Sayyed Jalil Mahdizadeh ◽  
Majid M. Heravi ◽  
Masumeh Heydari
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Computational Study ◽  
Reaction Pathway ◽  
Deep Insight ◽  
One Pot ◽  
Functional Theory ◽  
Three Component Reaction ◽  
High Yields ◽  
Mechanism Of The Reaction

A novel series of N-functionalized 4-aryl-tetrahydrobiquinoline-2,5-(1H,3H)-diones were synthesized in high yields by a one-pot three-component reaction involving 2-chloroquinoline-3-carbaldehydes, Meldrum’s acid, and enaminones (dimedone-based enaminones) in the presence of K2CO3 in CH3CN under reflux condition. To gain a deep insight on the mechanism of the reaction, an extensive series of quantum mechanics calculations in the framework of density functional theory (DFT) were carried out for supporting the suggested reaction pathway.

scholarly journals Divergent Reactivity of Indole-Tethered Ynones with Silver(I) and Gold(I) Catalysts: A Combined Synthetic and Computational Study

Synthesis ◽  
2018 ◽  
Vol 50 (24) ◽  
pp. 4829-4836 ◽  
Author(s):  
Jason Lynam ◽  
Richard Taylor ◽  
William Unsworth ◽  
John Liddon ◽  
James Rossi-Ashton ◽  
...  
Keyword(s):  
Ring Opening ◽  
Computational Study ◽  
Dft Study ◽  
Migration Mechanism ◽  
Catalyst Systems

A combined synthetic and computational (DFT) study has been performed to account for the divergent reactivity of indole-tethered ynones when treated with Ag(I) and Au(I) catalysts. The two catalyst systems deliver spirocyclic indolenines and carbazoles, respectively, from the same precursors, with the reaction outcomes believed to be a result of differences in the rates of a key protodemetalation step. A ring-opening/ring-closing isomerisation process is proposed to enable the interconversion of spirocyclic and C-2 annulated indole intermediates, in contrast to the 1,2-migration mechanism tentatively proposed in previous studies.

scholarly journals An ab initio study of the valence tautomerism of type B mesoionic rings

2019 ◽  
Vol 60 (32) ◽  
pp. 150876 ◽  
Author(s):  
Christopher A. Ramsden ◽  
Wojciech P. Oziminski
Keyword(s):  
Ab Initio ◽  
Ab Initio Study ◽  
Type B ◽  
Valence Tautomerism
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