Direct Amide Synthesis from Alcohols and Amines by Phosphine-Free Ruthenium Catalyst Systems

Amides are synthesized directly from alcohols and amines in high yields using an in situ generated catalyst from easily available ruthenium complexes such as the (p-cymene)ruthenium dichloride dimer, [Ru(p-cymeme)Cl-2](2), or the (benzene)ruthenium dichloride dimer, [Ru(benzene)Cl-2](2), an N-heterocyclic carbene (NHC) ligand, and a nitrogen containing L-type ligand such as acetonitrile. The phosphine-free catalyst systems showed improved or comparable activity compared to previous phosphine-based catalytic systems. The in situ generated catalyst from [Ru(benzene)Cl-2](2), an NHC ligand, and acetonitrile showed excellent activity toward reactions with cyclic secondary amines such as piperidine and morpholine.