Nickel-Catalyzed Hydroimination of Alkynes

A Modular and atom-efficient synthesis of 2-aza-1,3-butadiene:,derivatives, has been developed via nickel-Catalyzed intermolecular coupling between internal alkynes. and aromatic N-H ketimines. This novel alkyne hydroimination process, is promoted by a catalyst system of a Ni(0) precursor ([Ni(cod)(2)]), N-heterocyclic carbene (NHC) ligand (IPr), and Cs2CO3 additive. The exclusive formation of (Z)-enamine stereoisoimers is Consistent with a proposed anti-iminometalation of alkyne by pi-complexation with Ni(0) and subsequent attack by the N-H ketimine nucleophile. An NHC-ligated,Ni(0) pi-imine complex, [(IPr)(eta(1)-HN=CPh2)(eta(2)-HN=CPh2)], Was independently synthesized and displayed improved re-activity as the catalyst precursor.