Theoretical evaluation of phenyl-substituted aziridines, azirines and epoxides reactivity

The reactivity of three-membered heterocycles such as phenyl-substituted aziridines, azirines, epoxides was studied in comparison with styrenes, azomethines and carbonyl com-pounds which are most often used in organic synthesis in nucleophilic and electrophilic reactions. In accordance with electronic reactivity indices of nucleophilicity and electrophilicity calculated on the base of DFT approach, the substituted molecules of azirines, aziridines, and epoxides ex-hibit the similar reactivity to aldehydes and styrenes. In all cases, our predictions were checked against the experimental observations given in literature. All considered compounds mainly characterizes by the properties of medium-strength electrophiles. Aziridines, azirines, epoxides with two aryl groups show the best electrophilic properties. This observation can be used in predictions of reactivity for these classes of compounds. Among three-membered heterocycles, the best nucleophilic properties were observed for substituted epoxy cycles. We have found that the dual descriptor based on Fukui functions cannot be recommended for predictions the reactivity of aziridines and epoxides. The values of the dual descriptor on both carbon atoms in three-membered ring significantly differ, while the experimental data on nucleophilic addition indicate that the reaction proceeds at both carbon atoms. Nevertheless, for phenyl-substituted azirines, the descriptor based on Fukui functions shows its effectiveness quite well.