1,3-Steric Induction in Intermolecular Radical Reactions Mediated by a Co2(CO)6−Metal Core
1,3-Steric Induction in Intermolecular Radical Reactions Mediated by a Co2(CO)6−Metal Core
复制标题
Co2(CO)6−金属核介导的分子间自由基反应中的 1,3-空间诱导
DOI：
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发表时间：
2010
期刊：
影响因子：
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通讯作者：
Aaron A. Rowe
中科院分区：
文献类型：
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作者：
G. Melikyan;R. Spencer;Aaron A. Rowe
炔丙基偶联反应的非对映选择性可以通过使用γ-取代基的体积作为立体化学工具来控制。在γ-t-Bu和γ-Me 3Si基团中观察到这种1，3-空间诱导，这两种基团都有利于头对头偶合产物3，4-二取代1，5-二炔的d，l-构型（d，l- 95−100%）。X射线晶体学分析表明，聚集炔丙基自由基的最有利取向是其中体积大的γ-取代基彼此相对定位的取向。总的来说，使用Me 3Si辅助基团的合成策略包括五个步骤，并以28 - 33%的总产率提供纯的d，1 - 3，4-二芳基-1，5-己二炔，否则很难获得。
Diastereoselectivity of propargyl coupling reactions can be controlled by using the bulkiness of a γ-substituent as a stereochemical tool. This 1,3-steric induction was observed with γ-t-Bu and γ-Me3Si groups, both favoring a d,l-configuration of the head-to-head coupling products, 3,4-disubstituted 1,5-alkadiynes (d,l- 95−100%). X-ray crystallography analysis suggests that the most favorable orientation of converging propargyl radicals is the one in which the bulky γ-substituents are positioned anti to each other. Overall, the synthetic strategy of employing a Me3Si auxiliary group involves five steps and affords, with 28−33% overall yields, pure d,l-3,4-diaryl-1,5-hexadiynes, otherwise hardly accessible.