Catalytic Evaluation of Palladium Nanoparticles on Silica-Grafted n-Propyl-Diaza-15-Crown-5 (PNP-SGPDC) in the Heck and Suzuki Reactions

Silica-grafted n-propyl-diaza-15-crown-5 (SGPDC) with immobilized palladium nanoparticles was found as an efficient heterogeneous catalytic system for the Heck and Suzuki coupling reactions and satisfied results were obtained. Different derivatives of aryl halides and alkenes under the Heck reaction were converted to the corresponding products with good efficiency. The presence of electron-donating groups on the aryl moiety of aryl halide derivatives retarded the reaction and led to the drop of yields. In contrast, higher efficiency was observed when electron-withdrawing groups were accommodated on the aryl halide. As well as, a variety of bi-phenyl derivatives were well synthesized by the coupling reaction between aryl halides and aryl boronic acids derivatives via the Suzuki reaction. Reusability of the catalyst was examined in both Heck and Suzuki reactions under optimized conditions. The catalyst could be recycled several times without any treatment in its catalytic activity. The TEM image of the catalyst utilized in the Heck reaction after seven times of recyclability indicates that the morphology and size of the nanoparticles have remained almost intact.