立体选择性
化学
催化作用
超分子化学
环己酮
二肽
甲苯
脯氨酸
对称化
组合化学
立体化学
对映选择合成
有机化学
分子
氨基酸
生物化学
作者
Francisco Rodríguez‐Llansola,Juan F. Miravet,Beatriu Escuder
标识
DOI:10.1002/chem.201000654
摘要
L-Proline-L-valine dipeptide derivatives, which self-assemble in toluene, have been studied as stereoselective catalysts in the conjugate addition of cyclohexanone to trans-beta-nitrostyrene. Remarkable effects on the stereoselectivity are observed associated to the aggregation of the catalyst. Outstanding differences were observed between the catalytic activity of compound 1, which forms supramolecular gels in toluene, and compound 2, which is not a gelator. In the former case, the enantioselectivity of the reaction was almost insensitive to changes in catalyst concentration and temperature, but in the case of compound 2, the catalytic activity was very much affected by those variables. Structural studies indicate that the results can be rationalized by taking into account significant conformational changes experienced by the catalytic L-proline derivatives associated with the aggregation process. The results highlight that catalyst self-assembly is a very important issue to consider in the stereoselective outcome of organocatalytic reactions. Especially relevant is the fact that the use of supramolecular gels as organocatalysts emerges as a technique that affords reliable and constant stereoselectivity in different conditions with the added value of easy catalyst recovery.
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