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首页> 外文期刊>Chemistry: A European journal >The pivotal role of symmetry in the ruthenium-catalyzed ring-closing metathesis of olefins
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The pivotal role of symmetry in the ruthenium-catalyzed ring-closing metathesis of olefins

机译：对称性在钌催化的烯烃闭环复分解中的关键作用

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摘要

The synthesis of Ru-based precatalysts with N-heterocyclic carbene (NHC) ligands bearing syn- and anti-methyl groups on the NHC backbone and aryl N-substituents with differing steric bulk was carried out. The catalytic behavior of the monophospine Ru precatalysts (7 a, 7 b, 8 a, and 8 b) was compared to the corresponding family of phosphine-free catalysts (9 a, 9 b, 10 a and 10 b) in the ring-closing metathesis (RCM) of olefins. These catalysts showed high efficiency in RCM reactions and the syn-isomers 7 a and 9 a, in particular, proved to be among the most active catalysts in the formation of tetrasubstituted olefins through RCM. DFT studies on the entire RCM catalytic cycle of hindered olefins were performed to rationalize the different behaviors of catalysts with syn- and anti-methyl groups on the NHC backbone. Theoretical results not only disclosed how NHC symmetry influences the overall activity of the catalyst, but also gave relevant and more general indications on the crucial steps of the RCM of olefins.
机译：进行了带有N-杂环卡宾（NHC）配体的Ru基预催化剂的合成，该配体在NHC主链上带有同位和反甲基和具有不同空间体积的芳基N-取代基。将单膦Ru预催化剂（7a，7b，8a和8b）与相应的无膦催化剂系列（9a，9b，10a和10b）在环中的催化行为进行了比较。烯烃的封闭复分解（RCM）。这些催化剂在RCM反应中显示出高效率，并且特别是，同分异构体7a和9a被证明是通过RCM形成四取代的烯烃中活性最高的催化剂之一。对受阻烯烃的整个RCM催化循环进行了DFT研究，以合理化NHC主链上具有正甲基和反甲基基团的催化剂的不同行为。理论结果不仅揭示了NHC对称性如何影响催化剂的整体活性，而且还给出了有关烯烃RCM关键步骤的相关且更为笼统的指示。

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