Fluoride-free cross-coupling of organosilanols
Fluoride-free cross-coupling of organosilanols
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DOI：
10.1021/ja016021q
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发表时间：
2001-07-04
影响因子：
15
通讯作者：
Sweis, RF
中科院分区：
文献类型：
--
作者：
Denmark, SE;Sweis, RF
在过去的十年中，钯催化的有机硅化合物与有机卤化物的交叉偶联反应已经成为有机锡烷的成熟和通用的Stille-Migita-Kosugi偶联和有机硼烷的Suzuki-Miyaura偶联的可行替代方案。2 Kumada和Hiyama 3的开创性研究表明，通过添加氟化物源来促进钯催化的交叉偶联反应，可以活化有机官能硅化合物，以形成各种有机卤化物。自这一发现以来，氯代和氟代有机硅烷和原硅酸盐4已成功地用于交叉偶联反应。这些实验室最近披露的信息（方案1）已经证明了硅杂环丁烷、5a-c硅烷醇、5d、e甲硅烷基醚、5e和环状甲硅烷基醚5 f对于使用四丁基氟化铵的极其温和的交叉偶联反应的合成潜力虽然在推进有机硅交叉偶联的结构多样性方面已经取得了重大进展，一个严重的限制是使用氟化物源作为促进剂。对该试剂的需要排除了在例如其中任一偶联底物含有甲硅烷基保护基团的复杂分子合成中使用该反应。此外，TBAF并不便宜6a，并且它还使得大规模的反应后处理繁琐。在这里，我们报告了我们的成功努力，对非氟活化，有机硅交联使用廉价的市售试剂的发展。7我们发现，在TBAF·3 H2O的存在下，所有有机官能硅烷前体都会聚成一个共同的硅烷醇中间体，这阐明了硅上羟基所起的关键作用。[8]对于这种硅基交叉耦合的设施，一个有趣的建议是形成硅-
The palladium-catalyzed, cross-coupling reactions of organosilicon compounds to organic halides has, over the past decade, emerged as a viable alternative to the well-established and versatile Stille-Migita-Kosugi coupling of organostannanes1 and Suzuki-Miyaura coupling of organoboranes. 2 Pioneering studies by Kumada and Hiyama3 have shown that activation of organofunctional silicon compounds is possible by addition of a fluoride source to promote the palladium-catalyzed, cross-coupling reactions to various organic halides. Since this discovery, chloro-and fluoroorganosilanes and orthosiliconates4 have been successfully employed in cross-coupling reactions. Recent disclosures from these laboratories (Scheme 1) have demonstrated the synthetic potential of silacyclobutanes, 5a-c silanols, 5d, e silyl hydrides, 5e and cyclic silyl ethers5f for extremely mild cross-coupling reactions which employ tetrabutylammonium fluoride (TBAF ‚3H2O) as the activator.Although significant progress has been made in advancing the structural versatility of organosilicon cross-coupling, one serious limitation is the use of a fluoride source as the promoter. The need for this agent precludes employment of this reaction in, for example, complex molecule synthesis where either of the coupling substrates contains silyl protective groups. Moreover, TBAF is not inexpensive6a and it also makes reaction workup cumbersome on a large scale. Herein we report our successful efforts toward the development of a non-fluoride-activated, organosilicon crosscoupling using inexpensive commercially available reagents. 7 Our discovery that all of the organofunctional silane precursors converge to a common silanol intermediate in the presence of TBAF ‚3H2O illuminated the crucial role played by the hydroxyl group on silicon. 8 An intriguing proposal for the facility of this silicon-based cross-coupling is the formation of a silicon-