Organic–inorganic hybrid silica materials containing imidazolium and dihydroimidazolium salts as recyclable organocatalysts for Knoevenagel condensations

摘要: Organic–inorganic hybrid silica materials containing imidazolium and dihydroimidazolium salts prepared from monosilylated disilylated monomers by sol–gel methodologies are active reusable organocatalysts for the Knoevenagel condensation of aromatic aldehydes with malononitrile ethyl cyanoacetate under solvent-free conditions. Our immobilized systems present higher activities than related homogeneous bis-imidazolium salts, showing cooperative effect matrix surface additional advantage easy recycling. The best performances were obtained material derived polycondensation a salt in absence tetraethoxysilane (TEOS).