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

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... 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.