Stereoselective Nazarov cyclizations of bridged bicyclic dienones.
Stereoselective Nazarov cyclizations of bridged bicyclic dienones.
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DOI：
10.1021/ol051169q
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发表时间：
2005-06
期刊：
影响因子：
5.2
通讯作者：
R. Mazzola;T. D. White;H. Vollmer-Snarr;F. West
中科院分区：
文献类型：
--
作者：
R. Mazzola;T. D. White;H. Vollmer-Snarr;F. West
桥连双环二烯酮经历甲硅烷基导向的Nazarov环化，通常具有非常高的非对映选择性。在大多数情况下，观察到对具有外位环戊烯酮的产物的环化的强烈偏好。然而，在双环[3.2.1]辛烯体系的三碳桥中存在额外的不饱和度导致选择性完全逆转，只形成内环戊烯酮。观察到的选择性被认为是由空间和电子效应的组合产生的。
[reaction: see text] Bridged bicyclic dienones underwent silyl-directed Nazarov cyclization with generally very high diastereoselectivity. In most cases, a strong preference for cyclization to the product with an exo-disposed cyclopentenone was seen. However, the presence of additional unsaturation in the three-carbon bridge of a bicyclo[3.2.1]octadiene system caused complete reversal in selectivity with exclusive formation of the endo-cyclopentenone. The observed selectivities are believed to result from a combination of steric and electronic effects.