Origin of the synchronicity on the transition structures of polar Diels-Alder reactions. Are these reactions [4 + 2] processes?
The transition structures (TSs) for a series of related Diels-Alder reactions between cyclopentadiene and mono-, di-, tri-, and tetracyanoethylene derivatives have been studied with use of DFT methods at the B3LYP/6-31G computational level. The increase of the electron-withdrawing substitution on ethylene increases the rate of these polar cycloadditions. However, the symmetric arrangement of cis and trans 1,2-di- and tetracyanoethylenes decreases the effectiveness of the substitution, which can be related to the symmetry found at the corresponding TSs. A DFT analysis of the global and local electrophilicity power of these series of cyano ethylenes provides a sound explanation about the nature of these synchronous processes. The present theoretical study is in agreement with the experimental outcomes.
Domingo
Luis R
LR
Instituto de Ciencia Molecular, Universidad de Valencia, Dr. Moliner 50, 46100 Burjassot, Spain. domingo@utopia.uv.es
José Aurell
M
M
Pérez
Patricia
P
Contreras
Renato
R