TY - JOUR
T1 - Diels-Alder Reactivity of a Chiral Anthracene Template with Symmetrical and Unsymmetrical Dienophiles
T2 - A DFT Study
AU - Hernández-Mancera, Jennifer P.
AU - Núñez-Zarur, Francisco
AU - Vivas-Reyes, Ricardo
N1 - Funding Information:
We gratefully acknowledge the financial support provided by Administrative Department of Science, Technology and Innovation (Colciencias) within the Doctoral Scholarships Program, the Universidad de Cartagena (Cartagena, Colombia) for continuous support to our group and the Universidad de Medellín (Medellín, Colombia) for financial support and computational resources. The authors acknowledge the referees of the manuscript whose comments and suggestions considerably improved the quality of this manuscript.
PY - 2020/7/1
Y1 - 2020/7/1
N2 - In this work, we used Density Functional Theory calculations to assess the factors that control the reactivity of a chiral anthracene template with three sets of dienophiles including maleic anhydrides, maleimides and acetoxy lactones in the context of Diels-Alder cycloadditions. The results obtained here (at the M06-2X/6-311++G(d,p) level of theory) suggest that the activation energies for maleic anhydrides and acetoxy lactones are dependent on the nature of the substituent in the dienophile. Among all studied substituents, only −CN reduces the energy barrier of the cycloaddition. For maleimides, the activation energies are independent of the heteroatom of the dienophile and the R group attached to it. The analysis of frontier molecular orbitals, charge transfer and the activation strain model (at the M06-2X/TZVP level based on M06-2X/6-311++G(d,p) geometries) suggest that the activation energies in maleic anhydrides are mainly controlled by the amount of charge transfer from the diene to the dienophile during cycloaddition. For maleimides, there is a dual control of interaction and strain energies on the activation energies, whereas for the acetoxy lactones the activation energies seem to be controlled by the degree of template distortion at the transition state. Finally, calculations show that considering a catalyst on the studied cycloadditions changes the reaction mechanism from concerted to stepwise and proceed with much lower activation energies.
AB - In this work, we used Density Functional Theory calculations to assess the factors that control the reactivity of a chiral anthracene template with three sets of dienophiles including maleic anhydrides, maleimides and acetoxy lactones in the context of Diels-Alder cycloadditions. The results obtained here (at the M06-2X/6-311++G(d,p) level of theory) suggest that the activation energies for maleic anhydrides and acetoxy lactones are dependent on the nature of the substituent in the dienophile. Among all studied substituents, only −CN reduces the energy barrier of the cycloaddition. For maleimides, the activation energies are independent of the heteroatom of the dienophile and the R group attached to it. The analysis of frontier molecular orbitals, charge transfer and the activation strain model (at the M06-2X/TZVP level based on M06-2X/6-311++G(d,p) geometries) suggest that the activation energies in maleic anhydrides are mainly controlled by the amount of charge transfer from the diene to the dienophile during cycloaddition. For maleimides, there is a dual control of interaction and strain energies on the activation energies, whereas for the acetoxy lactones the activation energies seem to be controlled by the degree of template distortion at the transition state. Finally, calculations show that considering a catalyst on the studied cycloadditions changes the reaction mechanism from concerted to stepwise and proceed with much lower activation energies.
KW - activation strain model
KW - charge transfer
KW - chiral anthracenes
KW - DFT calculations
KW - Diels-Alder reactions
UR - http://www.scopus.com/inward/record.url?scp=85088831022&partnerID=8YFLogxK
U2 - 10.1002/open.202000137
DO - 10.1002/open.202000137
M3 - Artículo
AN - SCOPUS:85088831022
VL - 9
SP - 748
EP - 761
JO - ChemistryOpen
JF - ChemistryOpen
SN - 2191-1363
IS - 7
ER -