Cu 2 O/Graphene as an Efficient and Ligand Free Heterogeneous Catalyst for Ullmann Coupling of N–H Containing Compounds with Aryl Halides

The graphene supported Cu2O nanoparticles were prepared via a two-step liquid-phase method and exhibited high catalytic activity and stability for the Ullmann coupling of aryl halides with N–H containing compounds under mild and ligand-free conditions. The yield of C–N cross-coupling of imidazole with iodobenzene reached up to 97% with 0.5 mol% Cu (vs. reported 5–10 mol%). The high activity and stability of Cu2O/graphene are probably due to the unique structure of graphene, which can make Cu2O nanoparticles highly dispersed and prevent them from aggregation and oxidation.