A theoretical study of the intramolecular hetero Dials-Alder cycloadditionreactions of azoalkenes

Ab initio Hartree-Fock and density functional theory calculations were perf ormed to study transition geometries in intramolecular Diels-Alder cycloadd ition 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 i ntramolecular 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 sm all degree of asynchronicity, The DFT results are in full agreement with ex perimental evidence and show the capability of this level of DFT calculatio n to predict the reactivity of intramolecular hetero Diels-Alder cycloaddit ion correctly. (C) 2001 Elsevier Science B.V. All rights reserved.