An efficient ligand- and copper-free Sonogashira reaction catalyzed by palladium nanoparticles supported on pectin

A novel and green procedure for synthesis of Palladium nanoparticles (2–6 nm) supported on pectin, as a reductant and ligand is described. The synthesized catalyst was further successfully explored in copper, ligand- and amine-free Sonogashira–Hagihara coupling of various aryl iodides, bromides and chlorides as well as heteroaryl halides with phenylacetylene under aerobic conditions. It was found that the catalyst exhibited a high activity and selectivity for the Sonogashira–Hagihara reaction. The catalyst can be recovered and recycled by a simple filtration of the reaction solution with some decrease in catalytic activity.