Department of Chemistry, College of Natural Sciences, Chungnam National University, Daejeon 305-764, Korea.
J Org Chem. 2013 Sep 6;78(17):8242-9. doi: 10.1021/jo401420f. Epub 2013 Aug 19.
Functionality preferences of metathesis Ru carbenes to various alkenes and alkynes with electronic and steric diversity were determined by using time-dependent fluorescence quenching. The functionality preferences depend not only on the properties of multiple bonds but also on the ligands on Ru. There was a good correlation between functionality preference and the metathesis reaction outcome. The correlation between functionality preference and exo/endo product ratio offers a solution to resolve the mechanistic issue related with alkene- vs alkyne-initiated pathway in ring-closing enyne metathesis. The correlation indicates the preference is likely to dictate the reaction pathway and eventually the outcome of the reaction. The Ru catalyst favoring alkyne over alkene provides more endo product, indicating that the reaction mainly initiates at the alkyne. By changing the substitution pattern, the preference can be reversed to give an exclusive exo product.
利用时间相关荧光猝灭法测定了具有电子和空间多样性的复分解 Ru 卡宾与各种烯烃和炔烃的功能偏好。功能偏好不仅取决于双键的性质，还取决于 Ru 上的配体。功能偏好与复分解反应结果之间存在良好的相关性。功能偏好与外/内产物比之间的相关性为解决与环封烯炔复分解中烯烃与炔烃引发途径相关的机理问题提供了一种解决方案。相关性表明，这种偏好可能决定反应途径，并最终决定反应的结果。优先选择炔烃而不是烯烃的 Ru 催化剂提供了更多的内产物，表明反应主要在炔烃处引发。通过改变取代模式，可以将这种偏好反转，得到专有的外产物。
