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.