Theoretical Investigation of Regiodivergent Addition of Anilines and Phenolates to p-Benzoquinone Ring

Two different products were obtained by the regiodivergent reaction of benzoquinone derivatives with phenolates and anilines: 3-aryloxybenzoquinone and 2-phenylamino-3-bromobenzoquinone. Calculated density functional theory free energies of reaction values corroborate the experimental observation of the formation of the substitution product in the reaction with phenolates in acetonitrile and the product of addition/oxidation for the reaction with aniline in water. Calculated charges and Fukui functions are similar for C2 and C3 atoms, indicating an equal possibility to suffer a nucleophilic attack. The calculated energy barriers for nucleophilic attack steps indicated that the first steps of the substitution with phenolates and addition/oxidation with anilines are faster, which justifies the formation of the respective products. The natural bond order analysis for the transition states revealed that there is a strong interaction between lone pairs of N and O atoms and the pi C2C3* for the O -> C2 and N -> C3 attacks and a weak interaction for the O -> C3 and N -> C2 attacks, which also agrees with experimental observations.

Automated summary

Two different products were obtained by the regiodivergent reaction, with the formation of substitution product in the reaction with phenolates and addition/oxidation product in the reaction with aniline. The calculated energy barriers for the nucleophilic attack steps indicated that the initial steps of the reaction with phenolates and anilines were faster, justifying the formation of the respective products. The interaction between lone pairs of N and O atoms and the pi C2C3* for the O -> C2 and N -> C3 attacks tends to be stronger, while it is weaker for the O -> C3 and N -> C2 attacks, which agrees with experimental observations.