Highly selective ruthenium metathesis catalysts for ethenolysis.
Highly selective ruthenium metathesis catalysts for ethenolysis.
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DOI：
10.1021/ja200246e
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发表时间：
2011-05-18
影响因子：
15
通讯作者：
Grubbs, Robert H.
中科院分区：
文献类型：
--
作者：
Thomas, Renee M.;Keitz, Benjamin K.;Champagne, Timothy M.;Grubbs, Robert H.
N-芳基、N-烷基、N-杂环卡宾（NHC）钌复分解催化剂对油酸甲酯的乙烯醇分解具有高度选择性，相对于热力学自复分解产物，对动力学乙烯醇分解产物的选择性高达95%。本文所述的实施例代表了迄今为止用于乙烯醇分解反应的一些最具选择性的NHC基钌催化剂。此外，这些催化剂中的许多对作为亚甲基物质的增长显示出不寻常的偏好和稳定性，并且在相对低的催化剂负载量（<500 ppm）下提供良好的产率和转换数（TON）。催化剂的比较表明，钌配合物轴承空间位阻NHC取代基提供更大的选择性和稳定性，并表现出较长的催化剂寿命在反应过程中。动力学与热力学产物形成的催化剂偏好的比较分析是通过评价它们在末端烯烃的交叉复分解反应中的稳态转化率来实现的。这些结果与观察到的乙烯醇分解选择性一致，其中与显示出较高的交叉复分解产物转化率的选择性较低的催化剂相比，选择性较高的催化剂达到特征在于较低的交叉复分解产物转化率的稳态。
N-aryl, N-alkyl N-heterocyclic carbene (NHC) ruthenium metathesis catalysts are highly selective toward the ethenolysis of methyl oleate, giving selectivity as high as 95% for the kinetic, ethenolysis products over the thermodynamic, self-metathesis products. The examples described herein represent some of the most selective NHC-based ruthenium catalysts for ethenolysis reactions to date. Furthermore, many of these catalysts show unusual preference and stability toward propagating as a methylidene species, and provide good yields and turnover numbers (TONs) at relatively low catalyst loading (<500 ppm). A catalyst comparison showed that ruthenium complexes bearing sterically hindered NHC substituents afforded greater selectivity and stability, and exhibited longer catalyst lifetime during reactions. Comparative analysis of the catalyst preference for kinetic versus thermodynamic product formation was achieved via evaluation of their steady-state conversion in the cross-metathesis reaction of terminal olefins. These results coincided with the observed ethenolysis selectivities, in which the more selective catalysts reach a steady-state characterized by lower conversion to cross-metathesis products compared to less selective catalysts, which show higher conversion to cross-metathesis products.
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