A theoretical study of the intramolecular hetero Dials-Alder cycloaddition reactions of azoalkenes

Ab initio Hartree-Fock and density functional theory calculations were performed to study transition geometries in intramolecular Diels-Alder cycloaddition reactions of azoalkene compounds. The Hartree-Fock (HF) calculations were formed at the RHF/3-21G level and the density functional theory (DFT) calculations were performed with the B3LYP functional and 6-31G* basis set. The order of the reactivity of azoalkenes with different substituents in intramolecular hetero Diels-Alder reactions was predicted from the frontier orbital energies, and calculations of the reaction barriers were performed. The HF and DFT calculations generated transition geometries with a very small degree of asynchronicity, The DFT results are in full agreement with experimental evidence and show the capability of this level of DFT calculation to predict the reactivity of intramolecular hetero Diels-Alder cycloaddition correctly. (C) 2001 Elsevier Science B.V. All rights reserved.