ORGN 57 |
| There is growing interest in conjugated ene-ene-yne functionalities that when reacted thermally, photochemically, or in the presence of a transition metal, cyclize to form an external carbene or metal carbenoid. These types of cyclizations are not only interesting because of their uncommon mechanisms, but also provide access to novel classes of heterocycles or to known heterocycles with substitution patterns that are difficult to obtain. (2-alkynylphenyl)triazenes and (2-alkynylphenyl)phenyldiazenes, afford 2H-indazoles under mild, neutral conditions in excellent yields. Ethyne and butadiyne linked triazenes also cyclize in the expected manner yielding novel bisisoindazoles and ethyne linked isoindazoles. Along with synthetic work, the mechanistic aspects of these cyclizations have been analyzed using Density Functional Theory (DFT). Recently, this methodology has been extended to the Lewis-acid promoted cyclization of (2-phenylazo)benzonitriles affording isoindazole imines by way of isoindazolylnitrenes. In addition, novel transition metal coordination complexes of the isoindazoles are currently being investigated. The synthetic and mechanistic aspects of these various cyclizations will be presented herein.
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Heterocycles and Aromatics
1:00 PM-5:20 PM, Sunday, 26 March 2006 Georgia World Congress Center -- C301, Oral
Division of Organic Chemistry |
