Sequential Catalysis for the Production of Sterically Hindered Amines: Ru(II)-Catalyzed C-H Bond Activation and Hydrosilylation of Imines

Sequential ruthenium(II) catalyzed reactions for the production of secondary amines from simple imines are reported. They involve Ru(II)-acetate based catalytic systems for C-H Bond activation/diarylation of simple imines with aryl bromides followed by [RuCl2(arene)](2) hydrosilylation of diarylated imines. The direct diarylation of aldimines can be profitably produced by Ru(II) catalytic systems in the presence of both acetate and PPh3 ligands. By contrast, PPh3 additive disfavors diarylation of ketimines that is achieved with [Ru(OAc)(2)(p-cymene)] alone. The catalytic hydrosilylation of the resulting imines was simply performed with H2SiPh2 in the presence of [RuCl2(arene)](2) catalyst at room temperature leading to overall yield of 70-86% of secondary amines