A. Benallou1, H. Garmes2, N. Knouzi3, H. El Alaoui El Abdallaoui1*
1 Team of chemoinformatics research and spectroscopy and quantum chemistry, physical and chemistry lab.
2 Laboratory of bio-organic chemistry, Department of chemistry, Faculty of Science El Jadida.
University Chouaib Doukkali, B. P. 20, 24000
3 Laboratory Biomolecules and organic synthesis, Faculty of Science Ben M’Sik,
University Mohammedia – Casablanca, BP 7955 Casablanca Morocco
* Corresponding author. E-mail: email@example.com
Received: 24 March 2014; revised version accepted: 30 April 2014
In this work, we have elucidated the regioselectivity in some Hetero Diels–Alder [4+2] reactions essentially by means of the Hard and Soft Acid Base (HSAB) principle applied locally. On the basis of the Gazquez–Mendez conclusions, in the reaction between Isochalcogenazole (X = Se, Te) and Acetylenic dienophiles for the synthesis of polysubstituted Pyridines, we calculated the condensed local softnesses for the terminal atoms in order to show the preferential cyclization mode of these reactions confirm the ortho regioselectivity observed experimentally. The results obtained with the B3LYP/6-31G*/lanl2dz method has also been confirmed by the polar model of Domingo and by the application of the Houk rule. Thus, the choice of basis set level of calculation has no effect on the direction of the reaction and the parameters studied.
Keywords: Diels–Alder reactions; Regioselectivity; Local softnesses;