A DFT study on the regioselectivity and molecular mechanism of nitroethene [2 + 3] cycloaddition to (Z)-C,N-diphenylnitrone and C,C,N-triphenylnitrone

Global and local reactivity indexes indicate a polar character of the [2 + 3] cycloaddition of nitroethene to (Z)-C,N-diphenylnitrone and C,C,N-triphenylnitrone. The regioselectivity of the reactions is determined by the attack of an oxygen-centred nucleophilic site of the nitrone on the b-carbon atom in nitroethene, which is confirmed by B3LYP/6-31G(d) simulations of the reaction pathways. Although the transition complexes are considerably asymmetric and polar, the reactions proceed via a concerted mechanism.