An Analysis of the Regioselectivity of 1,3-Dipolar Cycloaddition Reactions of Benzonitrile N-Oxides Based on Global and Local Electrophilicity and Nucleophilicity Indices

摘要

The regioselectivity of the 1,3-dipolar cycloaddition (13DC) reactions of benzonitrile N-oxides (BNOs) with electrophilic and nucleophilic alkenes has been analyzed by using global and local nucleophilicity and electrophilicity reactivity in_dices defined within the conceptual DFT. The BNOs react with electron-deficient and electron-rich ethylenes, but the regioselectivities of these polar reactions are different. Whereas the reactions with electron-rich ethylenes are com_pletely regioselective, yielding 5-isoxazolines, a change in the regioselectivity is observed in the reactions with electron deficient ethylenes, which yield a mixture of 4- and 5_isoxazolines. Analysis of the energies, geometries, and elec_tronic structures of the transition-state structures involved in the 13DC reactions between the BNOs and two electronically activated ethylenes are in complete agreement with the analysis of the global and local electrophilicity and nucleo_philicity reactivity indices.