| Attributs | Valeurs |
|---|
| type
| |
| Is Part Of
| |
| Subject
| |
| Title
| - Origin of Enantioreversal in the Rhodium-CatalyzedAsymmetric Hydrogenation of Prochiral Enamides andthe Effect of the α-Substituent
|
| has manifestation of work
| |
| related by
| |
| Author
| |
| Abstract
| - Why does the sense of enantioselection change in going from substrate 1 to 2? Large-scale computations reproduce this trend and provide a general model for the α-substituent effect that converges with recent experimental results.
- The enantioselectivity of prochiral enamide hydrogenation depends on the structure ofthe enamide, with particular sensitivity to the nature of the α-substituent. Recently, Burkhas reported a spectacular example of structure sensitivity for [Rh(DuPHOS)]+-catalyzedenamide hydrogenations: although enamides containing either carboxyl or tert-butylα-substituents hydrogenate to ≥99% enantiomeric excess, the sense of enantioselection forthe two substrate classes is reversed. Why should the magnitude and sense of enantioselectivity depend so strongly on the enamide α-substituent? We report the application of QM/MM (ONIOM) computations to address this long-standing issue in asymmetric catalysis.Specifically, we demonstrate that computational methods reproduce the α-substituent effectin enamide hydrogenation catalysis and probe how the interaction of the enamide CC bondand the catalyst varies with the structure of the substrate. The picture that emergesemphasizes the complex confluence of both electronic effects (i.e., those effects that do notdepend on the size of the model system) and steric effects in controlling the stereochemistryof enamide hydrogenation reactions.
|
| article type
| |
| is part of this journal
| |
