A computational study of the electrocyclization of o-divinylbenzene and derivatives

Electrocyclization reactions of o-divinylbenzene and several derivatives were studied by performing density functional theory (DFT) calculations together with the 6-31+G∗ basis set. Reactants, products and transition states for each reaction were localized and the path connecting reactants and products was also obtained. Along the reaction path, magnetic properties were evaluated to elucidate the characteristics of the reactions studied. Considering the overall results obtained with different indexes, such as magnetic susceptibility, nucleus independent chemical shift (NICS) or anisotropy of the current-induced density (ACID), all the reactions were found to keep the main characteristics of pericyclic reactions, showing an enhanced aromaticity in the vicinity of the transition state. Only two cyclizations, involving an isocyanate or ketene group, arose some doubts about their behaviour, but both still showed characteristics of pericyclic reactions, though weakened with respect to prototypical electrocyclizations as that of o-divinylbenzene.