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Unravelling the Mechanism of Non–photoactivated [2+2] Cycloaddition Reactions: Relevance of Orbital Interactions and Zwitterionic Intermediates
Author(s) -
Arpa Enrique M.,
AguilarGalindo Fernando,
DíazTendero Sergio
Publication year - 2017
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201601743
Subject(s) - cycloaddition , atomic orbital , alkene , molecular orbital , chemistry , mechanism (biology) , computational chemistry , reaction mechanism , homo/lumo , concerted reaction , photochemistry , chemical physics , electron , physics , catalysis , organic chemistry , molecule , quantum mechanics
In this work, a thorough theoretical study of the [2+2] cycloaddition reaction between asymmetric substituted alkenes is presented. The simulations evidence a concerted asynchronous or stepwise mechanism, depending on the nature of the electron‐deficient alkene. We have found a direct relation between the interaction of the frontier‐orbitals (HOMO‐LUMO) and the distortion energy with the activation energy (whose values oscillate between ∼4 and ∼35 kcal/mol in the studied cases). We thus conclude that the interaction between the frontier‐orbitals govern the reaction, through changes in the distortion energy. We also show that the lifetime of the zwitterionic intermediate determine the relative stereochemistry of the products.