Reaction Electronic Flux Perspective on the Mechanism of the Zimmerman Di-π-methane Rearrangement

Abstract

The reaction electronic flux (REF) offers a powerful tool in the analysis of reaction mechanisms. Noteworthy, the relationship between aromaticity and REF can eventually reveal subtle electronic events associated with reactivity in aromatic systems. In this work, this relationship was studied for the triplet Zimmerman di-π-methane rearrangement. The aromaticity loss and gain taking place during the reaction is well acquainted by the REF, thus shedding light on the electronic nature of reactions involving dibenzobarrelenes.

Description of the Reaction Intermediate Stabilization for the Zimmerman Di-π-methane Rearrangement on the Basis of a Parametric Diabatic Analysis

“…To complement these results, the spin-density distributions for both triplet biradical intermediates ( BR1 and BR2 ) are shown in the inset of Figure a. The spin-density is delocalized in one of the benzene rings due to a transient dearomatization that this ring undergoes in BR1 , a fact that seems to be revealing more complexity in the mechanism, since the T 1 state antiaromaticity alleviation of DBB* is plausible and the so-called Baird’s rule for reversal of aromaticity in the triplet surface (T 1 ) could be eventually involved in the mechanism of the DPM rearrangement of 4-CDBB , even though it is not directly involved in the mechanism of the unsubstituted DBB …”

“…A direct 1,2-aryl shift skipping the BR1 intermediate has been ruled out in terms of bonding, although our previous studies on this reaction have demonstrated that the DPM rearrangement of DBB undergoes a competition of one- and two-step mechanisms due to the fact that the shallow intermediate ( BR1 ) on T 1 induces the occurrence of nonstatistical dynamics . Along the path on T 1 , the excited state aromaticity plays a relevant role on the reaction driving force, since the rearomatization of one of the benzene rings occurs on TS2 . Moreover, we have previously used the reaction electronic flux (REF) approach to find that very specific changes of electronic density in the molecule are associated with changes in aromaticity along the intrinsic reaction coordinate (IRC) …”

Mechanism for Intramolecular Proton Transfer in the Isomerization of Hydroxyacetone: A Detailed Characterization Based on Reaction Force Analysis and the Bond Fragility Spectrum

“…[48][49][50][51] Collectively, these properties represent a powerful toolkit for analyzing chemical reaction mechanisms and has been demonstrated in numerous studies. [52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70][71] The reaction force constant particularly has proven useful as an indicator of the synchronous/asynchronous nature of bond breaking/formation, it has been applied extensively to study synchronicity in Diels-Alder reactions. [72,73] Additionally, a recent method developed by Piotr Ordon and coworkers called the bond fragility spectrum aims to analyze the sequence of bond breaking/formation for a reaction by investigating the derivative of properties based on the molecular Hessian.…”

Symmetry-Adapted Perturbation Theory Decomposition of the Reaction Force: Insights into Substituent Effects Involved in Hemiacetal Formation Mechanisms

“…[20][21][22][23] Together these properties have been proven useful in providing new chemical insight in a wide variety of reaction mechanisms. [24][25][26][27][28][29][30][31][32][33][34][35][36] In addition to properties based on the total energy, fragment based approaches strive to provide additional insight by partitioning the chemical system into interacting monomers and describing the height of the activation energy barrier in terms of modulations of the original reactants. This idea was spearheaded by Morokuma in the early 1970s where he utilized energy decomposition schemes in order to analyze energy and force components for stable molecules.…”