A comparative theoretical study of the pericyclic-pseudopericyclic character in a group of cyclizations of dienylketenes to cyclohexadienones

作者：Pena Gallego A^*; Rodriguez Otero J; Cabaleiro Lago E M

来源：Journal of Physical Chemistry A, 2007, 111(15): 2935-2940.

DOI：10.1021/jp068772q

A comprehensive B3LYP/6-31+G* study of the nature of 6 pi electrocyclizations of four different dienylketenes (2-furanyl, 2-pyrrolyl, cyclopenta-1,3-dienyl, and 2-thiophenyl-substituted ketenes) to corresponding cyclohexadienones was carried out. An analogous system ((3Z)-4-(3H-pyrrol-2-yl)buta-1,3-dien-1-one) was also analyzed. For this purpose, the complete pathways were determined (reactants, products, transition states, and the IRC connecting reactants and products), and changes in different magnetic properties (magnetic susceptibility, chi, magnetic susceptibility anisotropy, chi(anis), and the nucleus-independent chemical shifts, NICS) were monitored along the reaction profiles with a view to estimating the aromatization associated to the processes. We have also applied the ACID (anisotropy of the current-induced density) method with the same intention. The deep analysis of the results indicates a pericyclic character of the processes for the dienylketenes despite the relatively small NICS values in the transition states. Only the reaction of (3Z)-4-(3H-pyrrol-2-yl)buta-1,3-dien-1-one presents pseudopericyclic character due to the in-plane attack of the lone pair on nitrogen.

• 出版日期2007-4-19