Tetraalkylammonium-based ionic liquids for a RuCl3 catalyzed C–H activated homocoupling

Abstract [BuEt3N][NTf2] can be a superior ionic liquid in a RuCl3 catalyzed oxidative C–H activation reaction compared to standard imidazolium-based ionic liquids. The tetraalkylammonium-based ionic liquid resulted in higher yields. This could be due to the absence of a possible C–H activation on the tetraalkylammonium-based ionic liquid itself. This side reaction could occur with imidazolium-based ionic liquids. The ionic liquid could be recycled and different oxidation agents could be used in the reaction. The best results were obtained with FeCl3 · 6H2O and with a combination of LiCl under an oxygen atmosphere. Up to 83% yield were obtained in the homocoupling of 2-arylpyridines.