ChemInform Abstract: STUDIES OF THE TRANSITION-STATE STRUCTURE BY THE METHOD OF VOLUMETRIC STERIC EFFECTS. PART 4. TRANSITION STATE IN DIELS-ALDER REACTIONS OF (E)-1-ALKYL(ALKOXY)-1,3-BUTADIENES WITH ALKYL ACRYLATES

1985 ◽  
Vol 16 (16) ◽  
Author(s):  
B. S. EL'YANOV ◽  
S. K. SHAKHOVA ◽  
B. D. POLKOVNIKOV ◽  
L. F. RAR
Keyword(s):  
Transition State ◽  
Diels Alder ◽  
Steric Effects ◽  
State Structure ◽  
Transition State Structure ◽  
Alkyl Acrylates

scholarly journals Computational Assessment and Understanding of C6 Product Selectivity for Chromium Phosphinoamidine Catalyzed Ethylene Trimerization

2021 ◽  
Author(s):  
Daniel Ess ◽  
Nathan Morgan ◽  
Steven Maley ◽  
Doo-Hyun Kwon ◽  
Michael Webster-Gardiner ◽  
...  
Keyword(s):  
Transition State ◽  
Hydrogen Transfer ◽  
Quantitative Modeling ◽  
Steric Effects ◽  
Computational Studies ◽  
Product Selectivity ◽  
State Structure ◽  
Transition State Structure ◽  
Highly Active ◽  
Ethylene Trimerization

One approach to selectively generate 1-hexene is through ethylene trimerization using highly active Cr N-phosphinoamidine catalysts ((P,N)Cr). Depending on the ligand, (P,N)Cr catalysts can either generate nearly pure 1-hexene or form 1-hexene with significant mixtures of other C6 mass products, for example methylenecyclopentane. Here we report DFT transition state modeling examining 1-hexene catalysis pathways as well as pathways that lead to alternative C6 mass products. This provided qualitative and semi-quantitative modeling of the experimental 1-hexene purity values for several (P,N)Cr catalysts. Consistent with previous computational studies, the key 1-hexene purity-determining transition states were determined to be β-hydrogen transfer structures from the metallacycloheptane intermediate. The origin of selectivity for these (P,N)Cr catalysts can be attributed to steric effects in the transition-state structure with coordinated ethylene that leads to C6 impurities.

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