Approaches to the synthesis of (+/-)-strychnine via the cobalt-mediated [2 + 2 + 2] cycloaddition: rapid assembly of a classic framework.
Approaches to the synthesis of (+/-)-strychnine via the cobalt-mediated [2 + 2 + 2] cycloaddition: rapid assembly of a classic framework.
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通过钴介导的[2 2 2]环加成合成(i-)-马钱子碱的方法：经典框架的快速组装。
DOI：
10.1021/ja016333t
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发表时间：
2001
影响因子：
15
通讯作者：
K. Vollhardt
中科院分区：
文献类型：
--
作者：
M. Eichberg;R. L. Dorta;D. Grotjahn;K. Lamottke;M. Schmidt;K. Vollhardt
本文介绍了五种外消旋士的宁的合成方法，其中以钴离子介导的炔与吲哚的[2 + 2 + 2]环加成反应为关键步骤。这些包括大环8的生成和尝试环化，以及二氢咔唑15、22和26的合成，以及它们分别通过共轭加成、偶极环加成和螺桨烷至螺稠合骨架重排形成五环结构。最后讨论了1的成功全合成。一个短的，高度收敛的路线（在最长的线性序列中的14个步骤）的发展是突出的环化enynoylindole 40与乙炔和正式的分子内1，8-共轭加成胺49形成pentaclidone 50。从乙烯基碘56形成1的哌啶环进行了许多尝试，并描述了通过钯、镍和自由基介导的方法成功形成。
Five synthetic approaches to racemic strychnine (1), with the cobalt-mediated [2 + 2 + 2] cycloaddition of alkynes to indoles as the key step, are described. These include the generation and attempted cyclization of macrocycle 8 and the synthesis of dihydrocarbazoles 15, 22, and 26 and their elaboration to pentacyclic structures via a conjugate addition, dipolar cycloaddition, and propellane-to-spirofused skeletal rearrangement, respectively. Finally, the successful total synthesis of 1 is discussed. The development of a short, highly convergent route (14 steps in the longest linear sequence) is highlighted by the cyclization of enynoylindole 40 with acetylene and the formal intramolecular 1,8-conjugate addition of amine 49 to form pentacycle 50. Numerous attempts toward the formation of the piperidine ring of 1 from vinyl iodide 56 were made and its successful formation via palladium-, nickel-, and radical-mediated processes is described.