Ruthenium catalyzed deaminative coupling of primary amines to secondary amines

Abstract

A mono-hydrido bridged dinuclear ruthenium complex, [{(η6-p-cymene)RuCl₂(μ-H-μ-Cl)] catalyzed deaminative coupling of primary amines to secondary amines is reported. Both benzylic and aliphatic primary amines are amenable in the catalysis, which delivers the symmetrical secondary amines. Catalytic synthesis of unsymmetrical secondary amines is attained upon employing anilines and different primary amines in which the anilines are alkylated by the primary amines. Notably, the catalysis does not require any additives or base. Reaction pathway involving N–H activation of primary amines leading to the formation of cationic ruthenium hydride intermediate in which the β-hydride elimination generates the imine ligand followed by intermolecular nucleophilic addition by primary amines that produces the secondary amines is proposed as a possible reaction mechanism. Ammonia is the only by-product in this transformation.

Graphical abstract

A bridged dinuclear ruthenium complex, [{(η6-p-cymene)RuCl₂(μ-H-μ-Cl)] catalyzed deaminative coupling of primary amines to secondary amines is reported. The mechanism involves N–H activation of primary amines leading the formation of cationic ruthenium hydride intermediate where the β-hydride elimination generates the imine ligand followed by intermolecular nucleophilic addition by primary amines.