Anorganische Chemie, Technische Universität Dortmund, Otto-Hahn-Strasse 6, 44227 Dortmund, Germany.
Chemistry. 2010 Apr 6;16(13):4048-62. doi: 10.1002/chem.200902551.
The direct alpha-lithiation of methyl-substituted silanes as an efficient method for the preparation and elaboration of Si-chiral compounds is reported. Deprotonation of chiral oligosilanes occurs selectively and with high yields at the methyl group of the stereogenic silicon center, even in the presence of multiple methylsilyl or methylgermyl substituents. Computational studies have confirmed this preference as a consequence of pre-coordination of the lithiating agent by the amino side-arm and repulsion effects in the corresponding transition state. This complexation is also obvious from X-ray structure analyses of the alpha-lithiated silanes, which exhibit intriguing structure formation patterns differing in the type of aggregation and the amount of alkyllithium used. An alternative route to Si-chiral compounds is also presented, which involves desymmetrization of dimethylsilanes mediated by a chiral side-arm. Structure analyses and computational studies have shown that the diastereoselectivity of this alpha-lithiation is influenced by the selectivity of the formation of the stereogenic nitrogen upon complexation of the alkyllithium.
本文报道了一种将甲基取代的硅烷进行直接 α-锂化反应，以高效制备和修饰 Si-手性化合物的方法。在手性寡硅烷中，即使存在多个甲硅烷基或甲锗基取代基，手性硅中心的甲基也能选择性地、高产率地发生脱质子反应。计算研究证实了这种优先性，这是由于亲核试剂与氨基侧臂预先配位以及在相应过渡态中的排斥效应所致。通过对 α-锂化硅烷的 X 射线结构分析也证实了这种络合作用，其表现出有趣的结构形成模式，在聚集类型和使用的烷基锂量上有所不同。本文还提出了一种制备 Si-手性化合物的替代途径，即通过手性侧臂介导的二甲基硅烷的去对称化反应。结构分析和计算研究表明，这种 α-锂化的非对映选择性受到烷基锂络合时形成手性氮的选择性的影响。
