Copper-Catalyzed Selective 1,2-Reduction of Quinolines.

Selective reduction of heteroaromatic compounds to partially hydrogenated, dearomatized molecules is a tantalizing task. A well-defined, air stable, and pyridine-based Cu(II) NNN pincer complex is developed, which catalyzes selective 1,2-reduction of quinolines. The unstable 1,2-hydrogenated quinolines are transformed into the corresponding amides and isolated in good yields. Mechanistic studies confirmed that the reaction proceeds via molecular species and the formation of an unexpected copper bimetallic intermediate, which facilitates the catalysis through metal-ligand cooperation.