Synthesis and characterization of guanine-functionalized mesoporous silica [SBA-16-G]: a metal-free and recyclable heterogeneous solid base catalyst for synthesis of pyran-annulated heterocyclic compounds

摘要

The synthesis of a new solid base catalyst, i.e., guanine-functionalized mesoporous silica [SBA-16-G], is described. The synthesized catalyst has been fully characterized by FTIR, solid state C-13 NMR, TGA, XRD, BET, FESEM, EDAX, CHNS elemental analysis, CO2-TPD, and TEM techniques. The surface area and the basicity of the synthesised [SBA-16-G] were found to be 524m(2)/g and 3.230mmol/g, respectively, based on BET and CO2-TPD analysis. The catalytic activity of the synthesized catalyst has been explored in the synthesis of a series of biologically and pharmaceutically active pyran-annulated heterocyclic compounds from a one-pot three-component reaction of an aromatic aldehyde, malononitrile/ethyl cyanoacetate, and a C-H activated acidic compound, in the presence of a catalytic amount (10wt%) of [SBA-16-G]. The catalyst is metal-free, easy to synthesize and to isolate from the reaction mixture, and recycled up to four times without significant loss of catalytic activity.