Abstract
Quantum chemical methods enable the investigation of chemical reaction mechanisms and must be considered a powerful tool for gaining a detailed understanding of chemical reactivity. Their state-of-the-art applications, known as ‘computational chemistry’ or ‘molecular modeling’ have been successful in drug design, biotechnology, and many other areas. However, their application to electron-rich heterocycles is hampered by so-called electron-correlation effects. The dramatic developments in computer technology and recent progress concerning the efficiency of quantum chemical algorithms allow for the investigation of these compounds and their reactions. Still, the sensitivity of the electronic structure of these molecules make such a task a subject to high-performance computing. The molecular class off uroxans and benzofuroxans are known as ‘electron-overcrowded’ and could thus not be treated reliably by computational methods at low levels. An overview is presented here that mainly deals with molecular rearrangements of benzofuroxans and nitrobenzofuroxans. Although most of these reactions are known for a long time their detailed mechanisms could not be explained based only on experimental evidence or at least gave rise to repeated speculations about the basic steps of the actual reaction paths. The progress in understanding the reactivity of benzofuroxans by means of computing the transition states of their reaction mechanisms is summarized.