Koenig, Burkhard and Pitsch, Wolfgang and Klein, Michael and Vasold, Rudolf and Prall, Matthias and Schreiner, Peter R. (2001) Carbonyl- and carboxyl-substituted enediynes: Synthesis, computations, and thermal reactivity. JOURNAL OF ORGANIC CHEMISTRY, 66 (5). pp. 1742-1746. ISSN 0022-3263
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The influence of electron-withdrawing groups (carbonyl and carboxyl) at the alkyne termini on the reactivity of enediynes was investigated by a combination of experimental and computational techniques. While the general chemical reactivity of such enediynes, especially if non-benzannelated, is increased markedly, the thermal cyclization, giving rise to Bergman cyclization products, is changed little relative to the parent enediyne system. This is evident from kinetic measurements and from density functional theory (DFT, BLYP/6-31G* + thermal corrections) computations of the experimental systems which show that the Bergman cyclization barriers slightly (3-4 kcal/mol) increase, in contrast to earlier theoretical predictions. The effect on the endothermicities is large (Delta DeltaH(r) = 7-12 kcal/mol). Hence, the increased reactivity of the substituted enediynes is entirely due to nucleophiles or radicals present in solution. This was demonstrated by quantitative experiments with diethylamine and tetramethyl piperidyl oxide (TEMPO) which both give fulvenes through 5-exo-dig cyclizations.
| Item Type: | Article |
|---|---|
| Uncontrolled Keywords: | BERGMAN CYCLIZATION; ENYNE-ALLENES; P-BENZYNES; AB-INITIO; DENSITY; ENERGY; CHEMISTRY; CYCLOAROMATIZATION; STABILITY; DESIGN; |
| Subjects: | 500 Science > 540 Chemistry & allied sciences |
| Divisions: | Chemistry and Pharmacy > Institut für Organische Chemie > Lehrstuhl Prof. Dr. Burkhard König |
| Depositing User: | Dr. Gernot Deinzer |
| Date Deposited: | 08 Feb 2022 16:37 |
| Last Modified: | 08 Feb 2022 16:37 |
| URI: | https://pred.uni-regensburg.de/id/eprint/41668 |
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