Construction of novel polycyclic ring systems by transition-metal-catalyzed cycloisomerization of ene-ene-ynes. Interception of a carbenoid intermediate in skeletal reorganization of enynes
Construction of novel polycyclic ring systems by transition-metal-catalyzed cycloisomerization of ene-ene-ynes. Interception of a carbenoid intermediate in skeletal reorganization of enynes
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DOI：
10.1021/ja981877p
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发表时间：
1998-09-09
影响因子：
15
通讯作者：
Seki, Y
中科院分区：
文献类型：
--
作者：
Chatani, N;Kataoka, K;Seki, Y
从简单、易得的原料合成复杂的有机分子是有机合成中具有挑战性的项目之一。1过渡金属催化的含烯-烯、2烯-二烯、3烯-炔、4-8烯-烯、9二烯-二烯、10、11二烯-炔、12和二烯-烯等两种不饱和元素的底物的环异构化，为将无环底物转化为环状化合物提供了一条有吸引力的途径，这是迄今为止用常规方法难以制备的。这种反应产生的环化产物保留了对进一步合成转化有用的功能。因此，很明显，环异构化反应是构建各种环体系的有力工具。含有三种或三种以上不饱和元素的底物的环异构化，如果能得到单一产物，将是构建新型环体系的另一种有用的方法。然而，这种反应是罕见的。最近，我们报道了rucl2和ptcl2催化的1,6 -烯基环戊烯的环异构化（骨架重组）。虽然Trost5和Mori6a各自独立地发现了形式上类似的转化，但这些反应的机制彼此不同。Trost提出钯环戊烯配合物（Pd (IV)）的中间作用是通过烯与Pd （II）的氧化环化，而Mori描述的反应显然是通过钌卡宾机制进行的。此外，在本实验室研究的催化反应的第一步似乎是金属卤化物与乙炔的络合。虽然我们对确切的反应机制知之甚少，但一种类碳中间体被认为起着关键作用。我们认为，如果类碳络合物是反应途径中的中间体，那么有可能使用含有已知与类碳络合物反应的适当物种的诱捕剂在原位捕获类碳络合物中间体。我们发现这可以用分子内烯烃来实现。18我们希望报告一个显著的催化反应，在这个反应中，不仅在环异构化中截获了第一中间体，而且还截获了第二中间体（式1）。这个反应包括四个碳碳键的形成。虽然这种多键参与反应看起来相当复杂，但它具有惊人的普遍性，并为多环框架提供了一条独特的途径。
The synthesis of complex organic molecules from simple, readily available starting materials is one of the challenging projects in organic synthesis. 1 The transition-metal-catalyzed cycloisomerization of substrates containing two elements of unsaturation, such as ene-ene, 2 ene-diene, 3 ene-yne, 4-8 eneallene, 9 diene-diene, 10, 11 diene-yne, 12 and diene-allene, 13 offers an attractive pathway for the conversion of acyclic substrates to cyclic compounds which have been difficult to prepare by conventional methods thus far. Such reactions give cyclized products which retain functionalities that are useful for further synthetic transformations. Thus, it is clear that cycloisomerization reactions represent a powerful tool for the construction of a variety of cyclic systems. The cycloisomerization of substrates which contain three or more elements of unsaturation would be a further useful method for the construction of novel ring systems if a single product could be obtained. However such reactions are rare. 14 Recently, we reported the RuCl2-and PtCl2-catalyzed cycloisomerization (skeletal reorganization) of 1, 6-enynes to 1-vinylcyclopentenes. 4 Although Trost5 and Mori6a independently discovered formally similar transformations, the mechanism of these reactions are different from one another. Trost proposed the intermediacy of the palladacyclopentene complex, a Pd (IV) complex, via the oxidative cyclization of enynes with Pd (II), and the reaction described by Mori clearly proceeds via a rutheniumcarbene mechanism. In addition, the first step in the catalytic reaction studied in this laboratory appears to be complexation of metal halides to an acetylene. 15 Although we have little information relative to the precise reaction mechanism, a carbenoid intermediate is proposed to play a key role. We reasoned that if the carbenoid complex is an intermediate in the reaction pathway, then it might be possible to trap in situ the carbenoid intermediate using trapping agents with appropriate species which are known to react with carbene complexes. 17 We found that this can be accomplished using an intramolecular olefin. 18 We wish to report a remarkable catalytic reaction in which interception of not only the first intermediate in the cycloisomerization but also the second intermediate has been achieved (eq 1). The reaction involves the formation of four carbon-carbon bonds. Although this multibond participating reaction seems rather complex, it is surprisingly general and provides a unique path to a polycyclic framework.