Half-Sandwich Ruthenium Complexes Bearing Hemilabile κ2-(C,S)-Thioether-Functionalized NHC Ligands: Application to Amide Synthesis from Alcohol and Amine

Amide synthesis is one of the most crucial transformations in chemistry and biology. Among various catalytic systems, N-heterocyclic carbene (NHC)-based ruthenium (Ru) catalyst systems have been proven to be active for direct synthesis of amides by sustainable acceptorless dehydrogenative Coupling of primary alcohols with amines. Most often, these catalytic systems usually use monodentate NHC and thus require an additional ligand to obtain high reactivity and selectivity. In this work, a series of cationic Ru(II)(eta(6)-p-cymene) complexes with thioether-functionalized N-heterocyclic carbene ligands (imidazole and benzimidazole-based) have been prepared and fully characterized. These complexes have then been used in the amidation reaction and the most promising one (i.e. 3c) has been applied on a large range of substrates. High conversions albeit with moderate yields have generally been obtained.

Automated summary

Amide synthesis is a crucial transformation in chemistry and biology. N-heterocyclic carbene-based ruthenium catalyst systems have been proven to be active for direct synthesis of amides. In this study, a series of Ru complexes with thioether-functionalized N-heterocyclic carbene ligands were prepared and applied to the amidation reaction, resulting in high conversions but moderate yields.