Intermolecular C-H insertions and cyclization reactions involving a stable germylene.
Intermolecular C-H insertions and cyclization reactions involving a stable germylene.
复制标题
涉及稳定亚甲锗烷基的分子间 C-H 插入和环化反应。
DOI：
10.1021/ja0026408
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发表时间：
2001
影响因子：
15
通讯作者：
J. Kampf
中科院分区：
文献类型：
--
作者：
Karla A. Miller;T. Watson;J. Bender;M. Holl;J. Kampf
大量的化学研究集中在CH活化和插入反应上，希望开发出将功能引入各种有机分子的通用方法。其中一个令人感兴趣的领域是有机腈中RCH键的插入和活化化学的发展。许多过渡和镧系金属基化学物质以前已经报道过。3-13本文报道了新的基于革米烯的分子间CH插入物，用于乙腈、苯基乙腈、丙腈和丁二腈。在探索二甲苯插入键腈RCH的普遍性时，发现己二腈以一种让人想起索普-齐格勒反应的方式环化。14,15然而，前所未有的C-CN键断裂步骤导致Ge-CN键的形成也发生了。虽然已知革米烯可以插入各种键，包括Si-H， 16 - Ge-H， 17和CX键，但18-22 CH和CC键通常对革米烯无反应。据我们所知，只有两例锗烯插入到任何类型的CH键中，这两例都是分子内的。23-25 Jutzi证明这种类型的CH插入可能是Lewis酸催化的。这种情况类似于1969年之前过渡金属烷烃的CH活化化学，当时已知许多分子内CH活化的“插入”例子，但尚未发现分子间的例子。26 Bis [Bis（三甲基硅基）甲基]germylene(1) 27在四氢呋喃（THF）和LiCl， MgCl2或LiBr存在下插入乙腈的RCH键，得到[(Me3Si) 2CH] 2GeH-(CH2CN)(2)，通过1H NMR光谱（方案1）进行定量监测。随着反应的完成，最初的亮黄色溶液逐渐变成清澈的淡黄色。丙腈、苯乙腈和丁二腈的反应活性相似，分别生成[(Me3Si) 2CH] 2GeH-[CH (CH3) CN](3)、[(Me3Si) 2CH] 2GeH [CH (C6H5) CN](4)和[(Me3Si) 2CH] 2GeH [CH (CN) CH2CN](5)。THF和特定盐的存在是插入反应所必需的。溶剂和盐对乙腈反应的影响已被广泛探讨。在不添加盐的情况下，用苯、乙醚或1,4 -二氧六环作为溶剂，在20℃下，1周内未发生反应。然而，当在苯的反应混合物中加入0.5 mol等量的THF时，根据1H NMR谱估计，在20℃下，反应在3天后缓慢地进行到~ 5%完成度。添加盐对反应速率也有显著影响。在THF溶剂中，反应分别在2分钟和20分钟内完成。加入2等量的MgCl2或LiCl。加入1.0等量的LiBr后，反应在1 h内完成。在Bu4NCl存在下，反应发生副反应，仅观察到微量CH插入产物。在不添加盐的THF中运行的反应表现出不同的反应速率，从30分钟到100分钟1周，取决于所使用的1批。这种速率的变化可能是由起始材料中的微量MgCl2杂质引起的。插入产物2-5经1H、13C NMR、IR、质谱等表征。2和3成功地进行了元素分析。对于2,4组SiMe3质子在0.11和0.13 ppm处有两个单线态，两个CH (SiMe3) 2质子在0.26 ppm (3JH-H) 3.2 Hz处有一个双线态，表明在锗中存在对称面。采用A2M2X自旋系统…
A great deal of chemical research has focused upon CH activation and insertion reactions in hopes of developing general methods for introducing functionality into a variety of organic molecules. 1, 2 One such area of interest has been the development of insertion and activation chemistry for the RCH bonds in organonitriles. A number of transition and lanthanide metal-based chemistries have been previously reported. 3-13 In this paper, novel germylene-based intermolecular CH insertions are reported for acetonitrile, phenyl acetonitrile, propionitrile, and succinonitrile. While exploring the generality of germylene insertion into the RCH of bond nitriles, it was discovered that adiponitrile cyclizes in a fashion reminiscent of the Thorpe-Zeigler reaction. 14, 15 However, an unprecedented C-CN bond breaking step leading to the formation of a Ge-CN bond also occurs. Although germylenes are known to insert into a variety of bonds including Si-H, 16 Ge-H, 17 and CX bonds, 18-22 both CH and CC bonds are generally unreactive to germylenes. To the best of our knowledge, only two cases of germylene insertion into any type of CH bond have been reported, both of which were intramolecular. 23-25 Jutzi demonstrated that this type of CH insertion may be Lewis acid-catalyzed. 24 This situation is similar to that of transition metal alkane CH activation chemistry prior to 1969 when many intramolecular “tuck-in” examples of CH activation were known, but no intermolecular examples had yet been discovered. 26 Bis [bis (trimethylsilyl) methyl] germylene (1) 27 inserts into the RCH bond of acetonitrile in the presence of tetrahydrofuran (THF) and LiCl, MgCl2, or LiBr to yield [(Me3Si) 2CH] 2GeH-(CH2CN)(2) quantitatively as monitored by 1H NMR spectroscopy (Scheme 1). The initially bright yellow solution faded to a clear, pale yellow color as the reaction proceeded to completion. Similar reactivity was observed for propionitrile, phenyl acetonitrile, and succinonitrile to yield [(Me3Si) 2CH] 2GeH-[CH (CH3) CN](3),[(Me3Si) 2CH] 2GeH [CH (C6H5) CN](4), and [(Me3Si) 2CH] 2GeH [CH (CN) CH2CN](5), respectively. The presence of THF and specific salts was essential for the insertion reaction. The effect of solvent and salt has been most extensively explored for the reaction with acetonitrile. For this substrate, no reaction occurred over a 1 week period at 20 C when benzene, diethyl ether, or 1, 4-dioxane were used as solvents in the absence of added salt. However, when 0.5 mol equiv of THF was added to the reaction mixture in benzene, the reaction slowly proceeded to∼ 5% completion after 3 days at 20 C as estimated by 1H NMR spectroscopy. The reaction rate was also dramatically affected by added salt. In THF solvent, the reaction is complete within 2 and 20 min, respectively, if g0. 2 equiv of MgCl2 or LiCl are added. Upon addition of 1.0 equiv LiBr the reaction is complete in 1 h. When the reaction was run in the presence of Bu4NCl, side reactions occurred, and only a trace of CH insertion product was observed. Reactions run in THF without added salt exhibit variable reaction rates, from 30 min to> 1 week, depending upon the batch of 1 employed. This variability in rate is likely caused by trace MgCl2 impurities in the starting material.Insertion products 2-5 were characterized by 1H and 13C NMR spectroscopy, IR and mass spectroscopies. Elemental analyses were successfully obtained for 2 and 3. For 2, the 1H NMR spectrum shows two singlets at 0.11 and 0.13 ppm for the four sets of SiMe3 protons and one doublet at-0.26 ppm (3JH-H) 3.2 Hz) for the two CH (SiMe3) 2 protons, indicating a plane of symmetry in the germane. An A2M2X spin system was used …