N -methylation of quinolines with CO 2 and H 2 catalyzed by Ru-triphos complexes

N-methyl-tetrahydroquinolines (MTHQs) are a kind of very useful chemicals, which can be obtained from N-methylation of amines. However, the methylation of quinolines which is a kind of highly unsaturated nitrogen-containing heterocyclic aromatic compounds has not been reported. In this work, we report the first work for the synthesis of MTHQs by methylation of quinolines using CO2 and H2. It was found that Ru(acac)3-triphos [triphos: 1,1,1-tris(diphenylphosphinomethyl)ethanl] complex was very active and selective for the N-methylation reaction of quinolines, and the yield of the desired product could reach 99%.