Alcohol promoted N-methylation of anilines with CO2/H2 over a cobalt catalyst under mild conditions

N-Methylation of amines with CO2/H-2 to N-methylamines over non-noble metal catalysts is very interesting but remains challenging. Herein, we present an alcohol (e.g., ethanol) promoted strategy for the N-methylation of anilines with CO2/H-2 with high efficiency under mild conditions (e.g., 125 degrees C), which is achieved over a cobalt catalytic system composed of Co(OAc)(2)center dot 4H(2)O, triphos and Sn(OTf)(2). This catalytic system has a broad substrate scope and is tolerant toward a wide range of anilines and N-methyl anilines, and a series of N,N-dimethyl anilines were obtained in high yields. Mechanism investigation indicates that the alcohol solvent shifts the equilibrium of CO2 hydrogenation by forming an alkyl formate, which further reacts with the amine to produce N-formamide, and Sn(OTf)(2) promotes the deoxygenative hydrogenation of N-formamides to afford N-methylamines. This is the first example of the N-methylation of amines with CO2/H-2 over a cobalt catalytic system, which shows comparable performance to the reported Ru catalysts and may have promising applications.