Interaction of 2-unsubstituted imidazole N-oxides with electron-deficient olefins: a quantum chemical analysis

Reactions between the model compound N-1,4,5-trimethyl-1H-imidazole-3-oxide and electron-deficient olefins including 2-(4-methoxybenzylidene)malononitrile, (E)-ethyl-2-cyano-3-(4-methoxyphenyl)acrylate, 2-benzoyl-3-(4-methoxyphenyl)acrylonitrile, and 5-(4-methoxybenzylidene)-2,2-dimethyl-1,3-dioxane-4,6-dione were theoretically studied in terms of the density functional theory. It was demonstrated that the reactions can proceed either by the 1,3-dipolar cycloaddition mechanism or by the Michael addition mechanism depending on the type of electron-withdrawing substituents in the olefin molecule. The reaction pathways were calculated and the intermediate structures were determined.