Chemistry of oxaziridines. 4. Asymmetric epoxidation of unfunctionalized alkenes using chiral 2-sulfonyloxaziridines: evidence for a planar transition state geometry

1983 ◽  
Vol 105 (10) ◽  
pp. 3123-3126 ◽  
Author(s):  
Franklin A. Davis ◽  
Mark E. Harakal ◽  
Sami B. Awad
Keyword(s):  
Transition State ◽  
Asymmetric Epoxidation ◽  
Transition State Geometry ◽  
Planar Transition

Transition State Geometry and Solvent Effects in the Enantioselective Oxidation of Sulfides to Chiral Sulfoxides by Oxaziridines

1995 ◽  
Vol 50 (9) ◽  
pp. 1396-1403
Author(s):  
Andreas Pointner ◽  
Rudolf Herrmann
Keyword(s):  
Transition State ◽  
Enantioselective Oxidation ◽  
Phenyl Sulfide ◽  
Methyl Phenyl Sulfide ◽  
Chiral Sulfoxides ◽  
Solvent Dependence ◽  
Transition State Geometry ◽  
Planar Transition ◽  
Better Than ◽  
Methyl Phenyl

AbstractFor the enantioselective oxidation of methyl phenyl sulfide and tert-butyl methyl sulfide to the corresponding chiral sulfoxides by 3,3-dibromo-(camphorsulfonyl)oxaziridine, semiempirical calculations (MNDO, AMI, PM3) concerning transition state geometries were performed. The results show that only PM3 is able to localize a transition state. For methyl phenyl sulfide, a spiro arrangement of the oxaziridine ring and the sulfur atom explains the observed direction of the selectivity better than a planar transition state. The solvent dependence of the observed enantioselectivity is related to the calculated dipole moment of the transition state by the Kirkwood-Onsager model. In THF as solvent, its direct participation in the transition state has to be considered

scholarly journals Advances in Automated Transition State Theory Calculations: Improvements on the AutoTST Framework

2020 ◽  
Author(s):  
Nathan Harms ◽  
Carl Underkoffler ◽  
Richard West
Keyword(s):  
Transition State ◽  
Kinetic Parameters ◽  
Transition State Theory ◽  
Vibrational Analysis ◽  
Chemical Kinetic ◽  
State Theory ◽  
Combustion Chemistry ◽  
Transition State Geometry ◽  
Substantial Progress ◽  
Symmetry Number

<div>Kinetic modeling of combustion chemistry has made substantial progress in recent years with the development of increasingly detailed models. However, many of the chemical kinetic parameters utilized in detailed models are estimated, often inaccurately. To help replace rate estimates with more accurate calculations, we have developed AutoTST, an automated Transition State Theory rate calculator. This work describes improvements to AutoTST, including: a systematic conformer search to find an ensemble of low energy conformers, vibrational analysis to validate transition state geometries, more accurate symmetry number calculations, and a hindered rotor treatment when deriving kinetics. These improvements resulted in location of transition state geometry for 93% of cases and generation of kinetic parameters for 74% of cases. Newly calculated parameters agree well with benchmark calculations and perform well when used to replace estimated parameters in a detailed kinetic model of methanol combustion.</div>

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