Catalysis of the Nitroso-Diels-Alder cycloaddition reaction between CH₃N=O and cis-1,3-butadiene by pnictogen...

Density functional theory calculations at the M06-2X/aug-cc-pVTZ level of theory have been used to examine the Nitroso-Diels-Alder (N-D-A) cycloaddition reaction between the CH₃N=O and cis-1,3-butadiene in the presence of PO₂X (X=F, Cl, OH) as a catalyst. The effect of the above PO₂X compounds on the activation energy of the N-D-A reaction, has been studied here. In the first stage, the energies of two different bonding interactions, via P⋯N versus P⋯O binding, between the PO₂X and CH₃N=O molecules were calculated. The results showed that the largest values of the interaction energy between the above molecules belong to the PO₂F, when connects to the nitrogen atom of the CH₃N=O. Also, calculations showed that all the above PO₂X compounds, decrease the activation energies of N-D-A reaction studied here via both P⋯N and P⋯O interactions. However, the largest effect on activation energies of the reaction belongs to the PO₂F catalyst when acts via P⋯N bonding. The activation strain model (ASM) was used to analyze the influence of the PO₂X catalyst on the studied reaction. The quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analysis were performed to understand the nature of forming interactions at the TS structures. The results of this study showed that the PO₂X (X=F, Cl, OH) compounds may be suggested as efficient catalysts for N-D-A reactions.