Elongated Gilman cuprates: the key to different reactivities of cyano- and iodocuprates.
Elongated Gilman cuprates: the key to different reactivities of cyano- and iodocuprates.
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伸长的吉尔曼铜酸盐：氰基铜酸盐和碘铜酸盐不同反应性的关键
DOI：
10.1021/ja501055c
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发表时间：
2014
影响因子：
15
通讯作者：
R. M. Gschwind
中科院分区：
文献类型：
--
作者：
M. Neumeier;R. M. Gschwind
在过去，关于氰基与碘铜酸盐的特殊反应性的长期存在且非常有争议的讨论集中在高阶铜酸盐结构的存在上。后来，大量的结构研究证明了碘和氰基吉尔曼铜酸盐及其衍生中间体的结构等价性。对于二甲基铜酸酯，也显示出类似的反应性。然而，在许多合成工作组中，关于氰基铜酸盐的高反应性的报道顽固地存在。在这项研究中，我们提出了一个替代的氰基和碘铜酸盐之间的结构差异，这是在协议双方的结果。关键是在反应过程中，烷基铜在碘代而不是氰基Gilman铜酸盐中的潜在结合。在具有高度可溶性取代基（R = Me3SiCH2）的铜酸盐的例子中，我们表明，在碘代铜酸盐的情况下，在反应过程中形成了几个富铜络合物，这消耗了额外的碘代铜酸盐，并提供较低的反应活性。为了证实这一点，各种高度可溶性的富铜配合物的合成，和它们的分子式，平衡的位置，它们的单体和它们的聚集趋势进行了研究，通过NMR光谱方法揭示扩展的碘吉尔曼铜酸盐。此外，测试了这些富铜络合物对与烷基卤化物的交叉偶联反应的产率的影响，导致碘铜酸盐的产率降低。因此，这项研究给出了一个解释，迄今为止混淆的结果，氰基和碘铜酸盐的相似和不同的反应性。在小的取代基的情况下，所产生的烷基铜沉淀和类似的反应性进行了观察。然而，具有大取代基的碘铜酸盐能够并入烷基铜单元。所得的富铜物质具有较少的极化烷基，即逐渐降低的反应性。
In the past the long-standing and very controversial discussion about a special reactivity of cyano- versus iodocuprates concentrated on the existence of higher-order cuprate structures. Later on numerous structural investigations proved the structural equivalence of iodo and cyano Gilman cuprates and their subsequential intermediates. For dimethylcuprates similar reactivities were also shown. However, the reports about higher reactivities of cyanocuprates survived obstinately in many synthetic working groups. In this study we present an alternative structural difference between cyano- and iodocuprates, which is in agreement with the results of both sides. The key is the potential incorporation of alkyl copper in iodo but not in cyano Gilman cuprates during the reaction. In the example of cuprates with a highly soluble substituent (R = Me3SiCH2) we show that in the case of iodocuprates during the reaction several copper-rich complexes are formed, which consume additional iodocuprate and provide lower reactivities. To confirm this, a variety of highly soluble copper-rich complexes were synthesized, and their molecular formulas, the position of the equilibriums, their monomers and their aggregation trends were investigated by NMR spectroscopic methods revealing extended iodo Gilman cuprates. In addition, the effect of these copper-rich complexes on the yields of cross-coupling reactions with an alkyl halide was tested, resulting in reduced yields for iodocuprates. Thus, this study gives an explanation for the thus far confusing results of both similar and different reactivities of cyano- and iodocuprates. In the case of small substituents the produced alkyl copper precipitates and similar reactivities are observed. However, iodocuprates with large substituents are able to incorporate alkyl copper units. The resulting copper-rich species have less polarized alkyl groups, i.e. gradually reduced reactivities.
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