Are Electrocyclization Reactions of (3Z)-1,3,5-Hexatrienone and Nitrogen Derivatives Pseudopericyclic? A DFT Study

Electrocyclization reactions of (3Z)-1,3,5-hexatrienone and nitrogen 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 IRC connecting reactants and products was also obtained. Magnetic properties were evaluated along the reaction path to elucidate the characteristics of the reactions studied. As obtained from the calculations, electrocyclization of (3Z)-1,3,5-hexatrienone is a pericyclic process, as indicated by a variety of indexes, such as Nucleus Independent Chemical Shift (NICS), anisotropy of the magnetic susceptibility, or anisotropy of the current-induced density (ACID). This reaction presents characteristics of pericyclic reactions despite the activation energy lowering relative to the electrocyclization of (4Z)-1,2,4,6-heptatetraene, and the relatively small NICS values observed in the transition state. Magnetic properties indicate that an enha...