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Decatungstate-photocatalyzed Si-H/C-H activation in silyl Hydrides: Hydrosilylation of Electron-poor Alkenes

Authors: 
Hisham Qrareya, Davide Ravelli, Maurizio Fagnoni, and Angelo Albini.
Journal Name: 
ChemCatChem,
Volume: 
7
Issue: 
33
Pages From: 
3350
To: 
3357
Date: 
Tuesday, October 6, 2015
Keywords: 
: photochemistry · silanes · radicals · reaction mechanisms · tungsten
Project: 
financial support from the Italian Ministry of Foreign Affairs through the E-PLUS project (Enhancementofthe Palestinian University System).
Abstract: 
Tetrabutylammoniumdecatungstate has been used for the photocatalytic activation of the Si-H bond in trisubstituted silanes and applied for the hydrosilylation of electron-poor alkenes. The mechanism that occurs depends on the silyl hydride used, as supported by laser flash photolysis and EPR trapping experiments. Homolytic Si-H cleavage through a hydrogen atom transfer from the silane to the excited catalyst operates with dimethylphenylsilane and methyldiphenylsilane, for which the hydrosilylation yields were satisfactory .If we used tertiary silanes that have more labile Si-H bonds, such as triphenyl silane or tris(trimethylsilyl)silane,the reaction worked to some extent even under uncatalyzed conditions because of a radical chain reaction. Competition between C¢Hand Si¢H cleavage was observed, however,if we used trialkyl silanes (e.g.,triethylsilane). In favorable cases,the process was also efficient under flow conditions or if promoted by sunlight