Highly active chiral ruthenium catalysts for asymmetric ring-closing olefin metathesis
Highly active chiral ruthenium catalysts for asymmetric ring-closing olefin metathesis
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DOI：
10.1021/ja055994d
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发表时间：
2006-02-15
影响因子：
15
通讯作者：
Grubbs, RH
中科院分区：
文献类型：
--
作者：
Funk, TW;Berlin, JM;Grubbs, RH
报道了含手性单齿氮杂环卡宾的烯烃复分解催化剂的合成及其在不对称关环复分解反应中的应用。这些催化剂保留了在相关的非手性变体（1 a和1 B）中发现的高水平的反应性。使用母体手性催化剂2a和2b以及在N-结合的芳基环的Meta位含有空间体积的衍生物（催化剂3-5），以高达92%ee形成五元至七元环。向催化剂2a-4a中加入碘化钠（原位形成2b-4 b）导致对许多底物的对映选择性急剧增加。在不添加NaI的情况下对某些底物产生高对映异构过量的催化剂5a可以以100%的负载量使用。
The synthesis of olefin metathesis catalysts containing chiral, moncidentate N-heterocyclic carbenes and their application to asymmetric ring-closing metathesis (ARCM) are reported. These catalysts retain the high levels of reactivity found in the related achiral variants (1 a and 1 b). Using the parent chiral catalysts 2a and 2b and derivatives that contain steric bulk in the meta positions of the N-bound aryl rings (catalysts 3-5), five-through seven-membered rings were formed in up to 92% ee. The addition of sodium iodide to catalysts 2a-4a (to form 2b-4b in situ) caused a dramatic increase in enantioselectivity for many substrates. Catalyst 5a, which gave high enantionneric excesses for certain substrates without the addition of Nal, could be used in loadings of