Radical Ring Expansion Reactions of Methylenecyclopropane Derivatives: A Theoretical Study
| Autor: | Diego Ardura, Tomás L. Sordo |
|---|---|
| Rok vydání: | 2006 |
| Předmět: |
Cyclopropanes
Free Radicals Double bond Stereochemistry Radical Ring (chemistry) chemistry.chemical_compound symbols.namesake Computer Simulation chemistry.chemical_classification Molecular Structure Organic Chemistry Solvation Stereoisomerism Silanes Methylenecyclopropane Gibbs free energy Kinetics Crystallography Models Chemical chemistry Cyclization Yield (chemistry) symbols Thermodynamics Solvent effects |
| Zdroj: | The Journal of Organic Chemistry. 71:4803-4809 |
| ISSN: | 1520-6904 0022-3263 |
| DOI: | 10.1021/jo0602625 |
| Popis: | The evolution of the primary radicals from 1-(3-bromopropyl)-2-ethyl-3-methylenecyclopropane, 1-(3-bromopropyl)-1-trimethylsilyl-2-methylenecyclopropane, 1-(3-bromobutyl)-2-ethyl-3-methylenecyclopropane, and 1-(3-bromobutyl)-1-trimethylsilyl-2-methylenecyclopropane was theoretically studied at the ROMP2/6-311++G(d,p)//UB3LYP/6-31G(d,p) theory level taking into account the effect of solvent through a PCM-UAHF model. For the propyl-substituted radicals, the attack of the radical center on the double bond takes place most favorably in an exo fashion. The subsequent ring expansions yield the product corresponding to the rupture of the endo C-C bond as the most favorable one in accordance with the experimental results. In the case of 1-(3-bromobutyl)-2-ethyl-3-methylenecyclopropane, the Gibbs energy barriers for the endo and exo attacks are the same, and the subsequent reversible evolution yields the product corresponding to the rupture of the exo C-C bond as the most favorable one through thermodynamic control in agreement with experiment. Finally, for 1-(3-bromobutyl)-1-trimethylsilyl-2-methylenecyclopropane, our calculations predict that the endo attack is 0.8 kcal/mol more favorable than the exo one. In the subsequent reversible ring expansion, the product corresponding to the rupture of the endo C-C bond is kinetically the most favored one in reasonable agreement with the experimental observations. |
| Databáze: | OpenAIRE |
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