Exo selectivity and the effect of disubstitution in the Diels–Alder reactions of butadiene with 3,3-disubstituted cyclopropenes

2004 ◽  
Vol 82 (11) ◽  
pp. 1589-1596 ◽  
Author(s):  
Tammy L Gosse ◽  
Raymond A Poirier
Keyword(s):  
Transition State ◽  
Density Functional ◽  
Computational Study ◽  
Alder Reaction ◽  
Diels Alder ◽  
Anomeric Effect ◽  
Isodesmic Reactions ◽  
Activation Barriers ◽  
Additional Stabilization ◽  
Transition State Structures

A density functional computational study was performed to accomplish two tasks: to examine the endo–exo selectivity in the Diels–Alder reactions of 3,3-disubstituted cyclopropenes with s-cis-butadiene, and to study the effect of disubstitution on the reactivity of the cyclopropene dienophile. Cyclopropene is substituted at C-3 with CH3, SiH3, NH2, PH2, OH, SH, F, and Cl; both 3-substituted and 3,3-disubstituted ground states are examined to determine relative reactivities. The exo transition-state structures are consistently lower in energy than the endo transition-state structures for the 3,3-disubstituted cyclopropene – butadiene system, and surprisingly, both modes of addition have lower activation barriers than the syn 3-substituted cyclopropene – butadiene system. Through a series of isodesmic reactions, we have concluded that there is an additional stabilization in the transition-state structures of the 3,3-disubstituted system that can account for the lowering of the activation barriers below that of the 3-substituted cases. This stabilization is a combination of the anomeric effect and the ring relaxation that occurs in the transition-state structure.Key words: Diels–Alder reaction, cyclopropene, exo selectivity, anomeric effect.

Density functional theory computational study on Diels–Alder reactions of cyclopentadiene with selected vinylsilanes and methylenecyclopropane

2011 ◽  
Vol 89 (3) ◽  
pp. 409-414 ◽  
Author(s):  
Nick Henry Werstiuk ◽  
Wojciech Sokol
Keyword(s):  
Density Functional Theory ◽  
Dft Calculations ◽  
Density Functional ◽  
Computational Study ◽  
Alder Reaction ◽  
Diels Alder ◽  
Rate Data ◽  
Synthetic Route ◽  
Functional Theory ◽  
Diels Alder Reaction

Aimed at predicting relative reactivities, density functional theory (DFT) calculations were carried out on a series of Diels–Alder reactions involving silylvinyl derivatives reacting with cyclopentadiene as part of a synthetic research project. Using three reactions for which experimental rate data are available to calibrate our calculations, we computationally pinpointed the best synthetic route to bicyclo[2.2.1]hept-5-ene-2,2-diylbis(trimethylsilane) (1). The synthesis begins with the Diels–Alder reaction of cyclopentadiene (2) with commercially available (1-bromovinyl)trimethylsilane (6).

Ab initio Cs transition state for the Diels-Alder reaction of acetylene and butadiene

1990 ◽  
Vol 55 (12) ◽  
pp. 3804-3807 ◽  
Author(s):  
James M. Coxon ◽  
Stephen T. Grice ◽  
Robert G. A. R. Maclagan ◽  
D. Quentin McDonald
Keyword(s):  
Transition State ◽  
Ab Initio ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction

scholarly journals A Computational Study of Direct CO2 Hydrogenation to Methanol on Pd Catalysts

2021 ◽  
Author(s):  
Igor Kowalec ◽  
Lara Kabalan ◽  
Richard Catlow ◽  
Andrew Logsdail
Keyword(s):  
Density Functional ◽  
Negative Charge ◽  
Computational Study ◽  
Adsorbed Species ◽  
Pd Catalysts ◽  
Functional Theory ◽  
Activation Barriers ◽  
Rate Determining Step ◽  
Adsorption Energies ◽  
Insight Into

<p>We investigate the mechanism of direct CO<sub>2</sub> hydrogenation to methanol on Pd (111), (100) and (110) surfaces using density functional theory (DFT), providing insight into the reactivity of CO<sub>2</sub> on Pd-based catalysts. The initial chemisorption of CO<sub>2</sub>, forming a partially charged CO<sub>2</sub><sup>δ-</sup>, is weakly endothermic on a Pd (111) surface, with an adsorption energy of 0.06 eV, and slightly exothermic on Pd (100) and (110) surfaces, with adsorption energies of -0.13 and -0.23 eV, respectively. Based on Mulliken analysis, we attribute the low stability of CO<sub>2</sub><sup>δ-</sup><sub> </sub>on the Pd (111) surface to a negative charge that accumulates on the surface Pd atoms interacting directly with the CO<sub>2</sub><sup>δ-</sup><sub> </sub>adsorbate. For the reaction of the adsorbed species on the Pd surface, HCOOH hydrogenation to H<sub>2</sub>COOH is predicted to be the rate determining step of the conversion to methanol in all cases, with activation barriers of 1.35, 1.26, and 0.92 eV on Pd (111), (100) and (110) surfaces, respectively.<br></p>

scholarly journals Popular Integration Grids Can Result in Large Errors in DFT-Computed Free Energies

2019 ◽  
Author(s):  
Andrea N. Bootsma ◽  
Steven Wheeler
Keyword(s):  
Transition State ◽  
Molecular Orientation ◽  
Density Functional ◽  
Basis Sets ◽  
Free Energies ◽  
Functional Theory ◽  
Metal Free ◽  
Stereoselective Reactions ◽  
Functionalization Reaction ◽  
Transition State Structures

<div>Density functional theory (DFT) has emerged as a powerful tool for analyzing organic and organometallic systems and proved remarkably accurate in computing the small free energy differences that underpin many chemical phenomena (e.g. regio- and stereoselective reactions). We show that the lack of rotational invariance of popular DFT integration grids reveals large uncertainties in computed free energies for isomerizations, torsional barriers, and regio- and stereoselective reactions. The result is that predictions based on DFT-computed free energies for many systems can change qualitatively depending on molecular orientation. For example, for a metal-free propargylation of benzaldehyde, predicted enantioselectivities based on B97-D/def2-TZVP free energies using the popular (75,302) integration grid can vary from 62:38 to 99:1 by simply rotating the transition state structures. Relative free energies for the regiocontrolling transition state structures for an Ir-catalyzed C–H functionalization reaction computed using M06/6-31G(d,p)/LANL2DZ and the same grid can vary by more than 5 kcal mol–1, resulting in predicted regioselectivities that range anywhere from 14:86 to >99:1. Errors of these magnitudes occur for different functionals and basis sets, are widespread among modern applications of DFT, and can be reduced by using much denser integration grids than commonly employed.</div>

scholarly journals Computational Study of Methane C–H Activation by Main Group and Mixed Main Group–Transition Metal Complexes

Molecules ◽  
2020 ◽  
Vol 25 (12) ◽  
pp. 2794
Author(s):  
Carly C. Carter ◽  
Thomas R. Cundari
Keyword(s):  
Transition Metal Complexes ◽  
Active Site ◽  
Density Functional ◽  
Computational Study ◽  
Divalent Metal ◽  
Main Group ◽  
Free Energies ◽  
Functional Theory ◽  
Activation Barriers ◽  
Experimental Values

In the present density functional theory (DFT) research, nine different molecules, each with different combinations of A (triel) and E (divalent metal) elements, were reacted to effect methane C–H activation. The compounds modeled herein incorporated the triels A = B, Al, or Ga and the divalent metals E = Be, Mg, or Zn. The results show that changes in the divalent metal have a much bigger impact on the thermodynamics and methane activation barriers than changes in the triels. The activating molecules that contained beryllium were most likely to have the potential for activating methane, as their free energies of reaction and free energy barriers were close to reasonable experimental values (i.e., ΔG close to thermoneutral, ΔG‡ ~30 kcal/mol). In contrast, the molecules that contained larger elements such as Zn and Ga had much higher ΔG‡. The addition of various substituents to the A–E complexes did not seem to affect thermodynamics but had some effect on the kinetics when substituted closer to the active site.

ChemInform Abstract: First Evidence of a Chair-Boat-Boat Transition State in the Transannular Diels-Alder Reaction.

ChemInform ◽  
2010 ◽  
Vol 25 (38) ◽  
pp. no-no
Author(s):  
Y. L. DORY ◽  
C. OUELLET ◽  
S. BERTHIAUME ◽  
A. FAVRE ◽  
P. DESLONGCHAMPS
Keyword(s):  
Transition State ◽  
Alder Reaction ◽  
Diels Alder ◽  
Diels Alder Reaction
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