Rummel Lars, König Henrik F, Hausmann Heike, Schreiner Peter R
Institute of Organic Chemistry, Justus Liebig University, Heinrich-Buff-Ring 17, 35392 Giessen, Germany.
J Org Chem. 2022 Oct 7;87(19):13168-13177. doi: 10.1021/acs.joc.2c01633. Epub 2022 Sep 27.
We present an experimental and computational study to investigate noncovalent interactions between silyl groups that are often employed as "innocent" protecting groups. We chose an extended cyclooctatetraene (COT)-based molecular balance comprising unfolded (1,4-disubstituted) and folded (1,6-disubstituted) valance bond isomers that typically display remote and close silyl group contacts, respectively. The thermodynamic equilibria were determined using nuclear magnetic resonance measurements. Additionally, we utilized Boltzmann weighted symmetry-adapted perturbation theory (SAPT) at the sSAPT0/aug-cc-pVDZ level of theory to dissect and quantify noncovalent interactions. Apart from the extremely bulky tris(trimethylsilyl)silyl "supersilyl" group, there is a preference for the folded 1,6-COT valence isomer, with London dispersion interactions being the main stabilizing factor. This makes silyl groups excellent dispersion energy donors, a finding that needs to be taken into account in synthesis planning.
我们开展了一项实验和计算研究，以探究常被用作“无害”保护基的硅烷基团之间的非共价相互作用。我们选择了一种基于扩展环辛四烯（COT）的分子天平，它由未折叠的（1,4 - 二取代）和折叠的（1,6 - 二取代）价键异构体组成，这两种异构体通常分别显示出硅烷基团的远程和近距离接触。通过核磁共振测量确定了热力学平衡。此外，我们在sSAPT0/aug - cc - pVDZ理论水平上利用玻尔兹曼加权对称适配微扰理论（SAPT）来剖析和量化非共价相互作用。除了极其庞大的三（三甲基硅基）硅基“超硅基”基团外，折叠的1,6 - COT价键异构体更受青睐，伦敦色散相互作用是主要的稳定因素。这使得硅烷基团成为出色的色散能量供体，这一发现需要在合成规划中予以考虑。
