On the Current Status of Ullmann-Type N-Arylation Reactions Promoted by Heterogeneous Catalysts

Ullmann-type C–N heterocoupling reactions have been applied for the syntheses of N-arylated amines. In the past decade, transition metal-catalyzed N-arylations have been recognized as particularly efficient procedures for the preparation of nitrogen-containing aromatic systems. These reactions typically carried out under optimized conditions, have also been found to be suitable for the synthesis of complex molecules with other functional groups, including natural products, drugs, or pharmaceuticals. Most importantly, copper-catalyzed N-arylations have been studied and employed in the total synthesis of biologically active compounds. The construction of fused N-heterocyclic compounds also remained the subject of extensive research because of their potential applications in drug discovery and the development of functional materials. The aim of this review is to summarize the recent progress in the synthetic applications of Ullmann-type N-arylation reactions performed in heterogeneous systems. In particular, the utilization of copper and palladium species immobilized on various support materials, modified by surface functionalization, has been discussed and evaluated.