The first fluoride-free Hiyama reaction of vinylsiloxanes promoted by sodium hydroxide in water

The first cross-coupling reaction between vinylalkoxysilanes and aryl bromides or chlorides promoted by aqueous sodium hydroxide under fluoride-free conditions to provide styrenes is reported. The reaction is catalyzed by palladium(II) acetate or a 4-hydroxyacetophenone oxime-derived palladacycle either under thermal or microwave heating at 120 degrees C with low catalyst loading (0.01-1 mol % of palladium) in the presence of tetra-n-butylammonium bromide (TBAB) as additive in air. In the case of styryltriethoxysilane, the coupling with aryl or vinyl bromides takes place stereospecifically to give the corresponding stilbenes or dienes, respectively. These mild and simple reaction conditions prevent undesirable polymerization of the products.