Internally cross-linked wrinkled fibrous silica nanocomposite by bipyridinum dichloride bridge: an efficient catalyst in the synthesis of α,β-unsaturated diketones

In this research, we designed a novel internally cross-linked wrinkled fibrous organo-silica nanocomposite containing bivalent organic cationic bridges in the framework. For this gold, bivalent organosilane bridging agent, Si(OEt) 3 -BiPy +2 2Cl - -Si(OEt) 3 was easily prepared through nucleophilic substitution reaction of (3-chloropropyl) triethoxysilane and bipyridine. In the next step, silanated bivalent cationic bipyridinium dichloride bridge was introduced into the pore walls of dendritic fibrous nanostructured silica through a sol−gel process under open-vessel reflux conditions. The obtained heterogeneous hybrid nanocomposite, KCC-1-Bipy +2 2Cl - , was characterized by FT-IR, EDX, TGA, and FE - SEM . The rationale was that such wrinkled fibrous, due to its abundant pores and slits, would acts as nanoreactor and would be an excellent catalyst in organic transformation due to the presence of quaternary ammonium units into the pore walls. Owing to the fact that the α-β-unsaturated carbonyl compounds can further be used in the synthesis of valuable intermediates, the catalytic ability of the nanocomposite was tested in the C=C bond formation reaction via Knoevenagel condensation of aldehyde and active methylene compounds under solvent free conditions. In addition to convenience, utilization of the catalyst with high catalytic activity and good reusability, makes this method as an interesting option for facile and efficient synthesis of α,β-unsaturated diketones derivatives.