DABCO-functionalized silica–copper(I) complex: a novel and recyclable heterogeneous nanocatalyst for palladium-free Sonogashira cross-coupling reactions

A DABCO-functionalized silica supported copper(I)-based nanocatalyst was successfully prepared using a novel and simple route, in which the DABCO as an important functional entity acts as both a stable linker and an excellent chelator. Initially, Cu(II) ions were fixed in the DABCO-functionalized SiO2 matrix via complex formation with N-groups of DABCO, and subsequently this Cu(II)-DABCO@SiO2 composite as a precursor reacted with NaI in methanol solvent at room temperature under aerobic conditions to produce the DABCO-functionalized silica–copper(I) complex (catalyst A). This catalyst was well characterized by FT-IR, CHN, XRD, FE-SEM, TEM, EDX, ICP-AES and TG analysis, and was found to be efficient and recyclable for the C–C bond formation reaction in the palladium-free copper-catalyzed Sonogashira coupling of aryl halides with phenylacetylene. The grafted DABCO, having a synergistic effect of coordination and electrostatic interactions, plays an important role in this catalytic system, and as an effective ligand and a quaternary ammonium salt, demonstrates an efficient stabilizing effect on the Cu(I) species.