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.
Full Text
The Full Text of this article is available as a PDF (1.5 MB).
References
- 1.Schleyer P.v.R. (ed.) (1998) Encyclopedia of Computational Chemistry. Wiley-Interscience, New York. [Google Scholar]
- 2.Feller D. & Davidson E.R. (1989) Basis Sets for Ab Initio Molecular Orbital Calculations and Intermolecular Interactions. In: Lipkowitz K.B. & Boyd D.B. (eds) Reviews in Computational Chemistry, Vol. 1, p. 1. VCH Publishers Inc., New York. [Google Scholar]
- 3.Ghosh P. Ternai B. & Whitehouse M. (1981) Benzofurazans and Benzo-furoxans: Biochemical and Pharmacological Properties. Med. Res. Rev. 1, 159. [DOI] [PubMed] [Google Scholar]
- 4.Eckert F. & Rauhut G. (1998) A Computational Study on the Reaction Mechanism of the Boulton-Katritzky Rearrangement. J. Am. Chem. Soc. 120, 13478. [Google Scholar]
- 5.Paton R.M. (1995) 1,2,5-Oxadiazoles. In: Katritzky A.R., Rees C.W. & Scriven E.F.V. (eds) Comprehensive Heterocyclic Chemistry II, Vol. 4, p. 229. Pergamon Press, New York. [Google Scholar]
- 6.Friedrichsen W. (1994) Arenofurazan-1-oxide, volume E8c. In: Schaumann E. (ed.) Houben-Weyl, Methoden der Organischen Chemie. p. 769. Thieme, Stuttgart. [Google Scholar]
- 7.Truhlar D.G., Garrett B.C. & Klippenstein S.J. (1996) J. Phys. Chem., 100, 12771, and references therein. [Google Scholar]
- 8.Ponder M., Fowler J.E., Schaefer H.F. (1994) Proposed Intermediates in the Tautomerization of Benzofurazan-1-Oxide. J. Org. Chem, 59, 6431. [Google Scholar]
- 9.Sedano E., Sarasola C., Ugalde J.M., Irazabalbeitia I.X., Guerrero A.G. (1988) Conformations and Charge Distributions in 1,2-Dinitrosoethylene and Furoxan 1. An ab Initio Molecular Orbital Study. J. Phys. Chem., 92, 5094. [Google Scholar]
- 10.Ugliengo P., Viterbo D. & Called M. (1988) Structural and Molecular Orbital Study of the Furazan N-Oxide System. Structures of 3-Amino-4-methylfurazan N-oxide and 4-Amino-3-methylfurazan N-Oxide, and Molecular Orbital Calculations, J. Chem. Soc. Perkin Trans. II, 661. [Google Scholar]
- 11.Seminario J.M., Concha M.C. & Politzer P. (1992) Calculated Structures and Relative Stabilities of Furoxan, Some 1,2-Dinitrosoethylenes and Other Isomers. J. Comput. Chem., 13, 177. [Google Scholar]
- 12.Rauhut G., Jarzecki A. & Pulay P. (1997) A Density Functional Based Vibrational Study of Conformational Isomers: The Molecular Rearrangement of Benzofuroxan. J. Comput. Chem., 18, 489. [Google Scholar]
- 13.Friedrichsen W. (1994) Benzofuroxan-o-Dinitrosobenzene Equilibrium. A Computational Study. J. Phys. Chem., 98, 12933. [Google Scholar]
- 14.Rauhut G. (1996) A Combined Ab Initio and Density Functional Study of the Ring-Chain Tautomerism in Benzofurazan-1-oxide. J. Comput. Chem., 17, 1848. [Google Scholar]
- 15.Katritzky A.R. & Gordeev M.F. (1993) Heterocyclic Rearrangements of Benzofuroxans and Related Compounds. Heterocycles, 35, 483. [Google Scholar]
- 16.Takakis I.M., Hadjimihalakis P.M., Tsantali G.G. & Pilini H. (1992) Convenient Preparation of 1,2-Alkylenedioxybenzofuroxans and Benzofurazans. J. Heterocyclic Chem. 29, 123. [Google Scholar]
- 17.Boulton A.J., Katritzky A.R. & Hamid A.M. (1967) Heterocyclic Rearrangements Part X. A Generalized Monocyclic Rearrangement. J. Chem. Soc. Sect. C, 2005. [Google Scholar]
- 18.La Manna G., Buscemi S. & Vivona N. (1998) Theoretical Study of Degenerate Boulton-Katritzky Rearrangements. Semiempirical and Ab Initio Procedures. J. Mol. Struct. (Theochem), 452, 67. [Google Scholar]
- 19.Horváth K., Korbonits D., Náray-Szabá G. & Simon K. (1986) Theoretical Considerations on the Extended Boulton-Katritzky Scheme. J. Mol. Struct. (Theochem), 136, 215. [Google Scholar]