Palladium-catalyzed cross-coupling reaction of alkenyldimethyl(2-pyridyl)silanes with organic halides: Complete switch from the carbometalation pathway to the transmetalation pathway
Palladium-catalyzed cross-coupling reaction of alkenyldimethyl(2-pyridyl)silanes with organic halides: Complete switch from the carbometalation pathway to the transmetalation pathway
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DOI：
10.1021/ja015655u
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发表时间：
2001-06-13
影响因子：
15
通讯作者：
Yoshida, J
中科院分区：
文献类型：
--
作者：
Itami, K;Nokami, T;Yoshida, J
过渡金属催化的交叉偶联反应构成了最通用和最有效的碳-碳键形成之一，并且改进的催化剂和试剂的开发继续以快速的速度发展。[1]尽管迄今为止已知有许多反应类型，但通过利用多功能底物来整合这些反应类型可能是由于难以控制这些单独的反应途径而远远落后。这将是非常重要的，在有机合成中，如果这样的多个反应途径是完美的控制，理想的添加剂或反应条件的轻微变化，并集成到顺序和/或一锅反应。在我们在这一领域的研究过程中，我们对乙烯基硅烷的多种形式的反应性产生了兴趣，乙烯基硅烷可以以两种不同的机理模式与有机卤化物和钯催化剂反应，即碳化途径（路径a，等式1）2，3和金属转移途径（路径B，等式1）。4虽然这两种反应途径在有机合成中得到了广泛的应用，但迄今为止还没有研究过它们的结合。最近，我们报道了钯催化的乙烯基（2-吡啶基）硅烷与有机卤化物的交联反应发生在碳化途径（途径a）中，以极高的产率得到取代的乙烯基（2-吡啶基）硅烷。3，5乙烯基硅烷的先前困难的Heck型反应的实现可能是由于吡啶基在硅上的强配位效应。在这次交流中，我们确定了（1）这种碳化途径（路径a）可以通过Pd/TBAF系统完全转换为金属转移途径（路径B），以及（2）这两种不同的反应途径可以通过Pd/TBAF系统完全转换。
The transition metal-catalyzed cross-coupling reactions constitute one of the most versatile and efficacious carbon-carbon bond formations, and the development of improved catalysts and reagents continues to evolve at a rapid pace. 1 Although there are a number of reaction types known to date, integration of these reaction types by utilizing a multifunctional substrate lags far behind presumably due to the difficulty in controlling those individual reaction pathways. It would be of great importance in organic synthesis if such plural reaction pathways were perfectly controlled, ideally with slight changes of additive or reaction conditions, and integrated into sequential and/or one-pot reactions. During the course of our investigations in this area, we became interested in the multiform reactivities of vinylsilanes, which can potentially react with organic halides and palladium catalyst in two mechanistically different modes, namely carbometalation pathway (path a, eq 1) 2, 3 and transmetalation pathway (path b, eq 1). 4 Although both of these reaction pathways have been extensively utilized in organic synthesis, their integration has not been examined to date.Recently we reported that the palladium-catalyzed crosscoupling reaction of vinyl (2-pyridyl) silanes with organic halides occurs in the carbometalation pathway (path a) to give the substituted vinyl (2-pyridyl) silanes in extremely high yields. 3, 5 The realization of the previously difficult Heck-type reaction of vinylsilane may be due to the strong coordination effect of the pyridyl group on silicon. In this communication, we establish that (1) this carbometalation pathway (path a) can be completely switched to the transmetalation pathway (path b) by the Pd/TBAF system and (2) these two distinct reaction pathways can be