TY - JOUR
T1 - Lithium Cation-Catalyzed Benzene Diels-Alder Reaction
T2 - Insights on the Molecular Mechanism within the Molecular Electron Density Theory
AU - Domingo, Luis R.
AU - Pérez, Patricia
N1 - Funding Information:
This work was supported by the Ministry of Science and Innovation (MICINN) of the Spanish Government, project PID2019-110776GB-I00 (AEI/FEDER, UE), and by FONDECYT, Chile, through Project no. 1180348.
Publisher Copyright:
© 2020 American Chemical Society. All rights reserved.
Copyright:
Copyright 2020 Elsevier B.V., All rights reserved.
PY - 2020/10/16
Y1 - 2020/10/16
N2 - The lithium cation Li+-catalyzed Diels-Alder (DA) reactions of benzene toward a series of acetylenes of improved nucleophilicity can be described within the context of the molecular electron density theory (MEDT) at the ωB97XD/6-311G(d,p) level. Conceptual density functional theory indices characterize the crown ether solvated complex benzene-lithium Bz-Li-Cro as a superelectrophile. Coordination of a lithium cation to benzene does not change substantially the electron localization function electronic structure of benzene. The DA reaction of Bz-Li-Cro with acetylene shows a reduction of the energy of activation of 6.9 kcal·mol-1, which is not sufficient for the reaction to take place, thus demanding the participation of strong nucleophilic acetylenes. DA reactions of complexes Bz-M-Cro (M = Li, Na, and K) are decelerated with the decrease of the ionization potential of the alkali metal. The one-step mechanism of these lithium cation Li+-catalyzed DA reactions changes to a two-step one for the reaction with dimethyl propynamine. The present MEDT study proves that analysis of the electrophilicity and nucleophilicity indices is an excellent tool for experimental organic chemists to understand, even to predict, the chemical organic reactivity.
AB - The lithium cation Li+-catalyzed Diels-Alder (DA) reactions of benzene toward a series of acetylenes of improved nucleophilicity can be described within the context of the molecular electron density theory (MEDT) at the ωB97XD/6-311G(d,p) level. Conceptual density functional theory indices characterize the crown ether solvated complex benzene-lithium Bz-Li-Cro as a superelectrophile. Coordination of a lithium cation to benzene does not change substantially the electron localization function electronic structure of benzene. The DA reaction of Bz-Li-Cro with acetylene shows a reduction of the energy of activation of 6.9 kcal·mol-1, which is not sufficient for the reaction to take place, thus demanding the participation of strong nucleophilic acetylenes. DA reactions of complexes Bz-M-Cro (M = Li, Na, and K) are decelerated with the decrease of the ionization potential of the alkali metal. The one-step mechanism of these lithium cation Li+-catalyzed DA reactions changes to a two-step one for the reaction with dimethyl propynamine. The present MEDT study proves that analysis of the electrophilicity and nucleophilicity indices is an excellent tool for experimental organic chemists to understand, even to predict, the chemical organic reactivity.
UR - http://www.scopus.com/inward/record.url?scp=85096318953&partnerID=8YFLogxK
U2 - 10.1021/acs.joc.0c01801
DO - 10.1021/acs.joc.0c01801
M3 - Article
AN - SCOPUS:85096318953
SN - 0022-3263
VL - 85
SP - 13121
EP - 13132
JO - Journal of Organic Chemistry
JF - Journal of Organic Chemistry
IS - 20
ER -