Synthesis of Stable Silaaromatic Compounds by Taking Advantage of Steric Protection

芳烃如苯和萘在有机化学中起着非常重要的作用，但是其中一些骨架碳被硅取代的硅杂芳族化合物非常不稳定，并且还没有这样的化合物的实例分离。在这项研究中，我们成功地合成了第一个硅芳族化合物的例子，1.e.，2-硅烷萘1，通过利用由空间保护基团2，4，6-三[双（三甲基甲硅烷基）甲基]苯基（Tbt基团）提供的动力学稳定。二氯四氢萘经还原、溴化、还原、再溴化得到1的直接前体。1用t-BuLi在己烷中脱溴得到无色晶体1。虽然1与水和氧气反应非常迅速，但它是热稳定的。其结构由^1H和1H <29>Si NMR以及X射线晶体学确定。特别值得注意的是<29>出现在Δ 87.4处的Δ Si信号，其指示sp_2Si的存在。此外，Cl-Si和Si-C3的^1J耦合常数分别为92和76 Hz，这清楚地表明硅萘环中的π电子存在一定程度的离域。还合成了另一种含2，6-双[双（三甲基硅基）甲基]-4-三[（三甲基硅基）甲基]苯基的2-硅萘。

Aromatic hydrocarbons such as benzene and naphthalene play a very important role in organic chemistry, but silaaromatic compounds where some of the skeletal carbons are replaced by silicon is very unstable and there has been no example isolation of such compounds. In this study, we have succeeded in the synthesis of the first example of a silaromatic compound, 1.e., 2-silanapthalene 1, by taking advantage of kinetic stabilization afforded by a sterically protecting group, 2,4,6-tris[bis (trimethylsilyl) methyl]phenyl (Tbt group). Reduction of dichlorinated tetrahydronapthalene followed by reaction with TbtLi, Bromination, reduction, and rebromination gave the direct precursor of 1. Debromination of 1 with t-BuLi in hexane gave 1 as colorless crystals. Although 1 reacts with water and oxygen very rapidly, it is thermally quite stable. The structure was established by ^1H and ^<29>Si NMR and X-ray crystallography. Of particular note is the ^<29>Si signal, which appear at delta 87.4, indicating the presence of sp_2 Si. Furthermore, the ^1J coupling constants of Cl-Si and Si-C3 are 92 and 76 Hz, respectively, clearly indicating that there is some delocalization of pi-electrons in the silanaphthalene ring. Another 2-silanaphthalene having 2,6-bis[bis(trimethylsilyl)methyl]-4-tris[(trimethylsilyl)methyl]phenyl group was also synthesized.