Elucidation of the regioselectivity in Diels–Alder reactions by means of theoretical approaches

Abstract

In this work, we have elucidated the regioselectivity in some Diels–Alder reactions essentially by means of the Hard and Soft Acid Base principle applied locally. On the basis of the Gazquez–Mendez conclusions, we calculated the condensed local softnesses for the terminal atoms in order to show the preferential cyclization mode of these reactions. The results obtained with the B3LYP/6-31G* method confirm the ortho regioselectivity observed experimentally. The regioselectivity of these reactions has also been confirmed by the calculation of the activation energies and by the application of the Houk rule.