N-Arylations of Nitrogen-Containing Heterocycles with Aryl and Heteroaryl Halides Using a Copper(I) Oxide Nanoparticle/1,10-Phenanthroline Catalytic System

A general procedure for solvent-free N-arylations of nitrogen-containing heterocycles, i.e. imidazoles, triazoles, and indoles, with aryl and heteroaryl halides catalyzed by copper(I) oxide (Cu 2 O) nanoparticles is demonstrated. Four types of Cu 2 O were evaluated: the bulky compound and its cubic, octahedral, and spherical nanoparticulate forms. The results show that Cu 2 O nanoparticles, in particular the cubic form, are highly efficient for the N-arylation reaction. In the presence of cubic Cu 2 O nanoparticles, 1,10-phenanthroline, and tetrabutylammonium fluoride, a variety of nitrogen-containing heterocycles smoothly underwent N-arylation with aryl and heteroaryl halides at 110-145 °C to give the corresponding products in moderate to excellent yields. It is noteworthy that the reaction is conducted under solvent-free conditions. The reaction mechanism is also discussed.