Metallation of Skeletal C-Atoms in Si-Methylated Carbosilanes

A very promising means for incorporating CH2 groups into the preparative scheme is via a selective acid-base reaction between — Me2Si—CH2—SiMe2— and LiR to produce — Me2Si—CHLi —SiMe2— + RH [103]. The solution to this task demands 

For this investigation, l,l,3,3,5,5-hexamethyl-l,3,5-trisilacyclohexane was chosen as model substance, because of its ability to undergo multiple lithiation and silylation reactions. Reaction of (Mc2Si—CH2)3 with n-BuLi/TMEDA in hexane in 2-3 hrs at 30 °C or 24 hrs at 20 °C quantitatively produced the monolithiated compound  

The reaction is thermodynamically controlled and the carbanion is stabilised by two adjacent SiMe2—CH2 groups. A kinetically controlled metallation of the SiMe group 

Quantitative silylation occurs on reaction with trimethylchlorosilane, in which no byproducts were observed 

Two possible reaction products are conceivable by reaction of 2M with n-BuLi  

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