Highly active recyclable heterogeneous Pd/ZnO nanoparticle catalyst: sustainable developments for the C–O and C–N bond cross-coupling reactions of aryl halides under ligand-free conditions

Abstract

Efficient Pd supported on ZnO nanoparticles for the ligand-free O-arylation and N-arylation of phenols and various N–H heterocycles with aryl chlorides, bromides, and iodides were readily synthesized and characterized. The amount of palladium on ZnO is 9.84 wt% (0.005 g of the catalyst contains 462 × 10−8 mol% of Pd) which was determined by ICP analysis. This nano sized Pd/ZnO with an average particle size of 20–25 nm and specific surface area 40.61 m2 g−1 was used as a new reusable heterogeneous catalyst for the formation of C–O and C–N bonds in organic synthesis. This protocol gives the arylated product in satisfactory yields without any N2 or Ar flow. The catalyst can be recovered and recycled several times without marked loss of activity.