Synthesis of Stable Silaaromatic Compounds by Taking Advantage of Steric Protection

芳香烃，如苯和萘在有机化学中起着非常重要的作用，但是硅芳族化合物的一些骨架碳被硅取代是非常不稳定的，而且还没有分离这类化合物的例子。在这项研究中，我们成功地合成了第一个硅芳化合物，1.e。利用空间保护基团2,4,6-三[双（三甲基硅基）甲基]苯基（Tbt基）提供的动力学稳定。二氯四氢萘还原，再与TbtLi反应，溴化，还原，再溴化，得到1的直接前驱体。1与t-BuLi在己烷中分解得到1为无色晶体。虽然1与水和氧反应非常快，但它在热上相当稳定。通过^1H和^<29>Si核磁共振和x射线晶体学确定了结构。特别值得注意的是^<29>Si信号，出现在δ 87.4处，表明sp_2 Si的存在。此外，Cl-Si和Si-C3的^1J耦合常数分别为92和76 Hz，清楚地表明在硅萘环中存在一定的pi电子离域。还合成了另一种具有2,6-二[二（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.