Interrupting the Nazarov reaction: domino and cascade processes utilizing cyclopentenyl cations
Interrupting the Nazarov reaction: domino and cascade processes utilizing cyclopentenyl cations
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DOI：
10.1039/b908515g
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发表时间：
2009-01-01
影响因子：
4.9
通讯作者：
West, Frederick G.
中科院分区：
文献类型：
--
作者：
Grant, Tina N.;Rieder, Curtis J.;West, Frederick G.
Nazarov反应需要共轭双阳离子的电环闭合以提供环戊烯基阳离子。在其常规方案中，允许该中间体通过损失相邻质子而进行消除，提供环戊烯酮产物。这篇专题文章描述了一类相对较新的多米诺和级联过程，其中Nazarov反应的机械过程在环戊烯基阳离子中间体的位置转移，统称为“中断Nazarov反应”。“各种分子内或分子间的亲核试剂，包括甲硅烷基、烯烃、芳烃、胺、卤化物、氧亲核试剂和叠氮化物，可以在一端捕获阳离子，从而产生有趣的多环结构。1，3-二烯也捕获环戊烯基阳离子，但在这种情况下通过协同[4 + 3]-环加成得到酮桥环辛烯。还讨论了从二氯环丙烷而不是交叉共轭二烯酮产生双环化前体的另一种方法，沿着一些新的捕获过程。
The Nazarov reaction entails the electrocyclic closure of a conjugated pentadienyl cation to furnish a cyclopentenyl cation. In its conventional protocol, this intermediate is allowed to undergo elimination through loss of an adjacent proton, providing cyclopentenone products. This feature article describes a relatively new class of domino and cascade processes in which the mechanistic course of the Nazarov reaction is diverted at the point of the cyclopentenyl cation intermediate, collectively referred to as "interrupted Nazarov reactions." A variety of intra- or intermolecular nucleophiles, including silyl hydrides, alkenes, arenes, amines, halides, oxygen nucleophiles and azides, can capture the cation at one terminus, resulting in interesting polycyclic structures. 1,3-Dienes also trap the cyclopentenyl cation, but in this case via concerted [4 + 3]-cycloaddition to give keto-bridged cyclooctenes. An alternative method for generating the pentadienyl cyclization precursor from dichlorocyclopropanes rather than cross-conjugated dienones is also discussed, along with some novel trapping processes.