On the Question of Zwitterionic Intermediates in the [3 + 2] Cycloaddition Reactions between C-arylnitrones and Perfluoro 2-Methylpent-2-ene

The molecular mechanism of the [3 + 2] cycloaddition reaction between C-arylnitrones and perfluoro 2-methylpent-2-ene was explored on the basis of DFT calculations. It was found that despite the polar nature of the intermolecular interactions, as well as the presence of fluorine atoms near the reaction centers, all reactions considered cycloaddition proceed via a one-step mechanism. All attempts for the localization of zwitterionic intermediates on the reaction paths were not successful. Similar results were obtained regardless of the level of theory applied.

Ab initio Study of Diels-Alder Reaction between Cyclic Dienes and Olefin

Theoretical modeling of organic synthesis is a powerful tool and leads to further insight into chemical systems. Computational chemistry allows obtaining the potential energy surface that experimentally cannot be observed, in addition to transition state calculations, which lead to better understanding the reactivity of an organic synthesis work. The Diels-Alder (DA) reaction of cyclopentadiene 1 and N-phenylmaleimide 2 has been studied at the MP2/6-311++G(d,p) level of theory. This DA reaction occurs through a one-step mechanism. It was expected that this reaction undergoes two regio-isomeric reaction paths passing through two different transition states to form two different products 3 and 4. The reaction paths are irreversible due to the exothermic character of -41.24 and -41.73 kcal.mol-1. This DA reaction are exergonic with reactions Gibbs free energies between -27.26 and -27.74 kcal⋅mol−1. Analysis of the CDFT indices predict the global electronic flux from the strong nucleophilic cyclopentadiene 1 to the electrophilic N-phenylmaleimide 2.