Assessment of the Electrochemical Synthesis Route to Silicones Starting from Silica as Feedstock

We successfully achieved methylation of various SiO2 sources to cyclic methylsiloxanes via electroreduction reaction. Contrary to previous assumptions, the reaction does not start from methanol as methyl radical source, that results in methoxylation of the electrolyte solvent. Methylammonium cations...

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Bibliographic Details
Published in:European journal of organic chemistry 2022-12, Vol.2022 (47), p.n/a
Main Authors: Beck, Alexander D., Schäffer, Lukas, Haufe, Stefan, Waldvogel, Siegfried R.
Format: Article
Language:English
Subjects:
Cations
Chemical synthesis
Comparative studies
Direct conversion
electrochemistry
Methyl radicals
Methylation
radicals
reduction
silicon
Silicon dioxide
Solvents
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Summary:We successfully achieved methylation of various SiO2 sources to cyclic methylsiloxanes via electroreduction reaction. Contrary to previous assumptions, the reaction does not start from methanol as methyl radical source, that results in methoxylation of the electrolyte solvent. Methylammonium cations were found to enable the direct conversion, strongly dependent on the radical intermediate stabilization by the electrolyte. THF/Bu4NCF3SO3 is the sole applicable system with yields below 14 % referred to the methylammonium cations for the highest amount of product obtained so far. Mechanistic insights show that methylation does not occur via the supposed hydrolysis of dimethoxydimethylsilane intermediate, but via a direct conversion reaction, as comparative studies of a Fenton‐type procedure clearly indicate. Further, cyclic methylsiloxane products are prone to subsequent electrochemical equilibration, strongly directed by the electrolyte solvent. A critical investigation on the direct electrochemical conversion of silica as raw materials to cyclic methylsiloxanes is reported. Room temperature synthesis of silicones could be achieved via the direct reduction of supporting electrolyte cations to methyl radical species. Requirements for the supporting electrolyte are high, mechanistic insights to vital intermediates and conditions are outlined.
ISSN:1434-193X
1099-0690
DOI:10.1002/ejoc.202201253