Catalytic C(sp²)–H Amination Reactions Using Dinickel Imides

Abstract

C–H amination reactions are valuable transformations for the construction of C–N bonds. Due to their relatively high bond dissociation energies, C(sp2)–H bonds are generally not susceptible toward direct nitrene insertion, necessitating alternative mechanisms for C–H activation. Here, we report that cationic dinuclear (NDI)Ni2 (NDI = naphthyridine–diimine) complexes catalyze intramolecular nitrene insertions into aryl and vinyl C(sp2)–H bonds. Mechanistic studies suggest that a bridging imido ligand supported at a Ni2 site induces C–H activation by a 1,2-addition pathway to generate an azametallacyclic intermediate. This organometallic mechanism contrasts with the electrocyclization/1,2-shift mechanism proposed for analogous transformations using Rh2 catalysts. The implications of these mechanistic differences for the stereoselectivity and chemoselectivity of C–H amination are described.