Hydrosilylation Reactions of C-C Multiple Bonds in Water. Comparative Study of the Radical Initiation Mechanisms

The classical radical-based hydrosilylation reaction of organic compounds bearing C-C multiple bonds is usually carried out in organic solvents and is herein presented in water with both organic solvent-soluble and water-soluble substrates. Different initiation methods to accomplish the radical-induced hydrosilylation reaction of C-C multiple bonds in water with (Me3Si)(3)SiH are presented. In the thermal decomposition of azo compounds, the system comprising substrate, silane, and azo-initiator (ACCN) mixed in aqueous medium at 100 degrees C worked well for both hydrophilic and hydrophobic substrates, with the only variation that the amphiphilic thiol HOCH2CH2SH was also needed in the case of the water-soluble compounds. Dioxygen initiation is shown to afford excellent yields of hydrosilylated products derived from substrates bearing C-C triple bonds and moderate to low yields of hydrosilylated products derived from C-C double-bonded compounds in water. Photochemical initiation in the absence of a chemical radical precursor other than the silane is also found to be a very efficient and convenient method to induce the hydrosilylation reaction of both C-C double and triple bonds of organic compounds hydrophilic and (hydrophobic substrates) with (Me3Si)(3)SiH in water. These three alternative radical-based methodologies studied in water are confronted.