Boron-Promoted Co-Catalyzed N-Methylation of Secondary Aromatic Amines with CO2 and H2

Development of catalytic methods using CO2/H-2 as methylating reagent for selective methylation of amines is highly attractive. Herein, the methylation of N-H bond via boron promoted activation of Co-formate intermediates is reported. This catalytic system showed excellent functional group tolerance with high catalytic activity, and a series of methylated products were acquired in moderate to excellent yields under mild conditions ( e.g. 80 degrees C or 60 degrees C ). It was inferred that imine complex C was the crucial intermediate formed via dehydration of species B , providing efficient C-N coupling for the selective N- methylation of secondary aromatic amines with CO2/H-2.