Facile synthesis of quinolines and N-alkylation reactions catalyzed by ruthenium(II) pincer type complexes: Reaction mechanism and evidences for ruthenium hydride intermediate

Amines, N-heterocyclic compounds, and their derivatives are ubiquitous in all naturally occurring compounds, particularly alkaloids, and are widely used in pharmaceuticals, agrochemicals, lubricants, and surfactants. The design of pincer type ligands and corresponding metal complexes is a fundamental step with a unique reactivity. In this article, the NNN-pincer type of ruthenium complexes were synthesized and analyzed using a variety of spectroscopic techniques, including UV-Visible, infrared, and NMR. The molecular structures of the complexes were examined by X-ray crystallography. These complexes were also employed to activate carbon and nitrogen (C-N bond) bonds in C-N coupling processes. This paper describes the synthetic approach, product purification, and spectroscopic characterization, and nuclear magnetic resonance (NMR) spectroscopy was used to demon-strate the catalytically synthesized substrates. A total number of 16 quinolines and 22 N-alkylated substrates were synthesized and characterized by NMR spectroscopic technique.