α-Alkylation of a norbornene-derived tricyclic ketone: are steric factors really in control?

2015 ◽  
Vol 51 (11) ◽  
pp. 2076-2079 ◽  
Author(s):  
Andrew M. Harned
Keyword(s):  
Dft Calculations ◽  
Conformational Preference ◽  
Torsional Strain ◽  
Steric Factors ◽  
Tricyclic Ketone

DFT calculations reveal that torsional strain and a strong conformational preference, rather than steric influences, dictate the observed stereoselectivity.

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.

Configuration and conformation of alkoxyalkyl and hydroxyalkyl trifluoromethyl nitroxides. Anomeric effects and nitroxide conformations

1981 ◽  
Vol 59 (12) ◽  
pp. 1745-1752 ◽  
Author(s):  
C. Chatgilialoglu ◽  
K. U. Ingold
Keyword(s):  
Anomeric Effect ◽  
Conformational Preference ◽  
Nodal Plane ◽  
Spectral Parameters ◽  
Small Magnitude ◽  
Or Groups ◽  
Steric Factors ◽  
Hyperfine Splittings ◽  
Anomeric Effects ◽  
Configuration And Conformation

The epr spectral parameters for some [Formula: see text] radicals have been measured over a range of temperatures. These radicals are probably non-planar at nitrogen. Their OR groups are in the eclipsed position with respect to the N 2pz orbital, a conformational preference which is attributed to a combination of steric factors and the anomeric effect. For [Formula: see text] the H hyperfine splittings (hfs) are of unusually small magnitude. It is pointed out that all other known [Formula: see text] also have anomalously low H hfs. It is suggested that this is due to the anomeric effect which not only promotes the eclipsed conformation but also causes the OR group to bend towards the semioccupied orbital, thereby moving H and R2 towards the nodal plane of this orbital.

scholarly journals Study of the influence of neighboring amino acids on proline conformation

2016 ◽  
Vol 5 (6) ◽  
pp. 627-631
Author(s):  
Jose Elias Cancino Herrera ◽  
Salvador Noriega ◽  
Shehret Tilvaldyev ◽  
Alfredo Villanueva Montellano ◽  
Alejandra Flores Ortega
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Dft Calculations ◽  
Energy Minimum ◽  
Conformational Preference ◽  
Peptide Bonds ◽  
The Third ◽  
Conformational Preferences ◽  
Two Systems

DFT calculations made at the B3LYP/6-31+G(d) level were used to investigate how the incorporation of a second amino acid into the backbone affects the conformational preferences of proline. Specifically, the this research studied the second amino acids L-proline and L-alanine and the trans isomerism of the peptide bonds. The lowest energy minimum has been found to have a different conformation for the two systems investigated; while the third presents a different conformation. The results obtained offer evidence of the influence of these systems on the conformational preference of proline.

Conjugative and steric factors affecting the conformational preference of some aromatic sulfides

1972 ◽  
Vol 37 (3) ◽  
pp. 504-505 ◽  
Author(s):  
G. Montaudo ◽  
F. Bottino ◽  
E. Trivellone
Keyword(s):  
Conformational Preference ◽  
Factors Affecting ◽  
Steric Factors

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.

scholarly journals Origins of Contrasteric π-Facial Selectivity in Epoxidations of Encumbered Tetrahydropyridines by a Bifunctional Peracid

Synlett ◽  
2019 ◽  
Vol 30 (04) ◽  
pp. 459-463 ◽  
Author(s):  
Shuming Chen ◽  
Sining Wang ◽  
K. Houk
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Bonding ◽  
Dft Calculations ◽  
Density Functional ◽  
Transition States ◽  
Conformational Preference ◽  
Functional Theory ◽  
Facial Selectivity

The origins of contrasteric diastereoselectivity in the epoxidation of encumbered tetrahydropyridines have been elucidated via density functional theory (DFT) calculations. A strong energetic preference for OH···N hydrogen bonding was found for epoxidation transition states of the unsubstituted tetrahydropyridine. For hexasubstituted tetrahydropyridines, the diastereofacial selectivity is dictated by both the strong OH···N hydrogen bonding and the conformational preference of the tetrahydropyridine substrate.

The C6 configuration and syn/anti conformational preference of the bisulfite adducts of deoxyuridine and deoxycytidine by NMR and DFT calculations

2014 ◽  
Vol 25 (20-21) ◽  
pp. 1355-1359 ◽  
Author(s):  
Karel D. Klika ◽  
Peter Schüler ◽  
Aubry K. Miller
Keyword(s):  
Dft Calculations ◽  
Conformational Preference

Structure elucidation of a proton-deficient natural product using LR-HSQMBC supported by DFT calculations

Planta Medica ◽  
2015 ◽  
Vol 81 (11) ◽  
Author(s):  
J Saurí ◽  
STS Chan ◽  
AV Buevich ◽  
KR Gustafson ◽  
RT Williamson ◽  
...  
Keyword(s):  
Dft Calculations ◽  
Natural Product ◽  
Structure Elucidation

pKa of Organoselenium Compounds: Ab Initio and DFT Calculations

2007 ◽  
Author(s):  
Sajjad Karamat ◽  
Juraj Kona ◽  
Walter Fabian
Keyword(s):  
Dft Calculations ◽  
Ab Initio ◽  
Organoselenium Compounds ◽  
Ab Initio And Dft
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