Selective Hydrosilylation of 1,3-Diynes Catalyzed by Titania-Supported Platinum

Titania-supported platinum (mainly as Pt(II)) has been found to effectively catalyze the hydrosilylation of 1,3-diynes at 70 degrees C with low catalyst loading (0.25 mol %) under solvent-free conditions. Monohydrosilylation was achieved for diaryl-substituted diynes, whereas dialkyl-substituted diynes were transformed into the corresponding dihydrosilylated products in good yields. In every case, the process was proven to be highly stereoselective, with syn addition of the silicon hydrogen bond, and regioselective, with the silicon moiety exclusively bonded to the most internal carbon atom of the 1,3-diyne (beta-E product), as confirmed by X-ray crystallography.