N-Monomethylation of Aromatic Amines with Methanol via PNP-Pincer Ru Catalysts.

The use of methanol for the selective methylation of aromatic amines with RuHCl(CO)(PNP) (PNP = bis(2-diphenylphosphinoethyl)amine) is reported. Various aromatic amines were transformed into their corresponding monomethylated secondary amines in high yields at 150 °C with a very low catalyst loading (0.02-0.1 mol %) in the presence of KO Bu (20-60 mol %). The catalyst precursor, RuHCl(CO)(PNP), was converted to [RuH(CO)(PNP)] under the catalytic conditions and also serves as a highly effective catalyst. The robustness of this catalyst contributes to its outstanding catalytic activity, even under reaction conditions, in which CO is liberated from methanol.