Dirhodium(II)-catalyzed regio- and stereoselective cycloisomerization towards 6,5,3-tricyclic skeletons containing vicinal all-carbon quaternary stereocenters,Organic Chemistry Frontiers

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Dirhodium(II)-catalyzed regio- and stereoselective cycloisomerization towards 6,5,3-tricyclic skeletons containing vicinal all-carbon quaternary stereocenters
Organic Chemistry Frontiers ( IF 4.6 ) Pub Date : 2024-07-25 , DOI: 10.1039/d4qo00998c
Zurong Xu ₁ , Jiajun Lu ₁ , Huanfeng Jiang ₁ , Rui Wu _{1,

2} , Shifa Zhu _{1,

2}

Affiliation

The construction of multicyclic frameworks and all-carbon quaternary stereocenters is among the most important and challenging tasks in organic synthesis. Therefore, the development of an efficient catalytic method for the direct and stereoselective construction of multicyclic frameworks bearing vicinal all-carbon quaternary stereocenters is highly desirable. Herein, we report a Rh₂(II)-catalyzed regio- and stereoselective cycloisomerization of benzo-fused 1,6-enynes, which enables rapid construction of 6,5,3-tricyclic skeletons containing two consecutive all-carbon quaternary stereocenters with high efficiency (up to 98% yield) and excellent enantioselectivity (up to 99% ee). In this process, an exclusive cis-olefin and a unique alkenyl cyclopropane motif are constructed in one step. Mechanistic studies and the crystal structures of alkyne–dirhodium complexes reveal that the cooperative weak hydrogen bonding between the substrates and the dirhodium catalyst may enable the occurrence of cycloisomerization. Further control experiments indicated that the selectivity of 5-exo or 6-endo cyclization could be regulated by changing the reactive site of 1,2-hydride migration.

中文翻译：

二铑(II)催化的区域选择性和立体选择性环异构化为含有邻位全碳四元立构中心的6,5,3-三环骨架

多环骨架和全碳四元立构中心的构建是有机合成中最重要和最具挑战性的任务之一。因此，开发一种有效的催化方法来直接和立体选择性地构建带有邻位全碳四元立构中心的多环骨架是非常必要的。在此，我们报道了Rh ₂ ( II )催化的苯并稠合1,6-烯炔的区域和立体选择性环异构化，该反应能够快速构建包含两个连续全碳四元立构中心的6,5,3-三环骨架，具有高效率（高达 98% 收率）和出色的对映选择性（高达 99% ee）。在此过程中，一步构建了独特的顺式烯烃和独特的烯基环丙烷基序。炔烃-二铑配合物的机理研究和晶体结构表明，底物和二铑催化剂之间的协同弱氢键可能导致环异构化的发生。进一步的对照实验表明，5-外环或6-内环化的选择性可以通过改变1,2-氢化物迁移的反应位点来调节。

更新日期：2024-07-25

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