Iterative Synthesis of Oligosilanes Using Methoxyphenyl- or Hydrogen-Substituted Silylboronates as Building Blocks: A General Synthetic Method for Complex Oligosilanes

Organosilanes have attracted the attention of researchersfor morethan 150 years due to their unique properties, and they have becomeindispensable industrial assets. However, many synthesized oligosilaneswith multiple Si-Si bonds are relatively simple, i.e., theyoften only contain a single repeating unit. More laborious customizedsynthetic routes can lead to more complex oligosilanes, but comparedto carbon-based molecules, their structural diversity remains limited.The development of effective and practical synthetic routes to complexoligosilanes that contain mixed substituents constitutes a long-standingchallenge. Here, we describe an iterative synthesis of oligosilanesusing methoxyphenyl- or hydrogen-substituted silylboronates, whichwere obtained via transition-metal-catalyzed Si-H borylationreactions. The first key reaction is a cross-Si-Si bond-formingreaction between chloro(oligo)silanes and silylboronates activatedby MeLi. The second key reaction is the selective chlorination ofthe methoxyphenyl group or the hydrogen atom at the terminal of theoligosilanes. Iteration of these two key reactions enables the synthesisof various oligosilanes that are otherwise difficult to access. Asa demonstration of the synthetic utility of this iterative syntheticapproach, oligosilanes with different sequences were prepared by simplychanging the order of the reaction of four different silicon units.Furthermore, a bespoke tree-shaped oligosilane is easily obtainedvia the present iterative synthesis. The solid-state structures ofseveral of these oligosilanes were unequivocally determined usingsingle-crystal X-ray diffraction analysis.

Automated summary

Organosilanes have attracted researchers' attention for their unique properties and are important industrial assets. This study presents an iterative synthesis method using methoxyphenyl- or hydrogen-substituted silylboronates obtained through transition-metal-catalyzed Si-H borylation reactions. This method enables the synthesis of various difficult-to-access oligosilanes by changing the reaction order of different silicon units.