Well-Defined N-Heterocyclic Carbene Based Ruthenium Catalysts for Direct Amide Synthesis from Alcohols and Amines

Well-defined N-heterocyclic carbene based ruthenium complexes were developed as highly active catalysts for direct amide synthesis from alcohols and amines. A catalytic amount of a base such as KOtBu was essential to initiate the catalytic cycle. Activity of the Ru complexes was comparable with the reported in situ Ru catalysts. These catalysts provided mechanistic insight suggesting a Ru hydride species as an active catalytic intermediate. The generation of the Ru hydride was critical for the amidation of free aldehydes.