Unsupported Copper Nanoparticles in the Arylation of Amines
Varvara I. Fomenko, Arina V. Murashkina, Alexei D. Averin, Anastasiya A. Shesterkina, I. P. Beletskaya
Abstract
Commercially available copper and copper (II) oxide nanoparticles (CuNPs and CuO NPs) were characterized using TEM and electronography methods to elucidate their true average size and composition. The catalytic amine arylation using unsupported copper nanoparticles differing in their size and copper oxidation state was investigated. The reaction of the model iodobenzene with n-octylamine was shown to be successfully catalyzed by CuNPs of average size 25 and 10/80 nm in the presence of the ligands such as 2-isobutyrylcyclohexanone (L1) and rac-1,1′-bi-2-naphthol (BINOL, L2), giving high yields (up to 95%) of the target N-octylaniline. CuO in bulk and nano forms was shown to be almost equally efficient in this process. Studies on the Cu-catalyzed amination of substituted iodobenzenes and 2-iodopyridine, as well as the arylation of different aliphatic amines and NH-heterocycles, verified that CuNPs (25 or 10/80 nm) with L1 and L2 are the most versatile and efficient nanocatalysts for a variety of substrates. Investigation of copper leaching under different conditions was carried out.