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A Density Functional Theory Study on the Electrocyclization of 1,2,4,6‐Heptatetraene Analogues: Converting a Pericyclic to a Pseudopericyclic Reaction
Author(s) -
CabaleiroLago Enrique M.,
RodríguezOtero Jesús,
GarcíaLópez Rosa M.,
PeñaGallego Angeles,
HermidaRamón Jose M.
Publication year - 2005
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.200401234
Subject(s) - pericyclic reaction , electrophile , lone pair , conrotatory and disrotatory , aromatization , chemistry , computational chemistry , nitrogen atom , superatom , carbon atom , density functional theory , molecule , organic chemistry , ring (chemistry) , catalysis
A comprehensive B3LYP/6‐31+G* study on the electrocyclization of 1,2,4,6‐heptatetraene analogues was conducted. Starting from the cyclization of (2 Z )‐2,4,5‐hexatrienal, a pericyclic disrotatory process favored by the assistance of a electron lone pair, we incorporated small modifications in its molecular structure to obtain a truly pseudopericyclic process. To this purpose electronegative atoms (fluorine and nitrogen) were added to give a more electrophilic character on the carbon atom which is attacked by the electron lone pair of the oxygen atom. The complete pathway for each reaction was determined, and changes in magnetic properties were monitored with a view to estimating the aromatization associated with each process. This information, together with the energetic and structural results, allowed us to classify the reactions as pseudopericyclic or pericyclic. Among all studied reactions only one was a truly pseudopericyclic process and another was a borderline case. The features of this unequivocally pseudopericyclic case were analyzed in depth.