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How Alkali Cations Catalyze Aromatic Diels‐Alder Reactions
Author(s) -
Vermeeren Pascal,
Brinkhuis Francine,
Hamlin Trevor A.,
Bickelhaupt F. Matthias
Publication year - 2020
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.202000009
Subject(s) - chemistry , alkali metal , diels–alder reaction , catalysis , computational chemistry , aromaticity , diene , context (archaeology) , photochemistry , organic chemistry , molecule , paleontology , natural rubber , biology
We have quantum chemically studied alkali cation‐catalyzed aromatic Diels‐Alder reactions between benzene and acetylene forming barrelene using relativistic, dispersion‐corrected density functional theory. The alkali cation‐catalyzed aromatic Diels‐Alder reactions are accelerated by up to 5 orders of magnitude relative to the uncatalyzed reaction and the reaction barrier increases along the series Li + < Na + < K + < Rb + < Cs + < none. Our detailed activation strain and molecular‐orbital bonding analyses reveal that the alkali cations lower the aromatic Diels‐Alder reaction barrier by reducing the Pauli repulsion between the closed‐shell filled orbitals of the dienophile and the aromatic diene. We argue that such Pauli mechanism behind Lewis‐acid catalysis is a more general phenomenon. Also, our results may be of direct importance for a more complete understanding of the network of competing mechanisms towards the formation of polycyclic aromatic hydrocarbons (PAHs) in an astrochemical context.