Rigidifying Ag(I) Complexes for Selective Nitrene Transfer

Abstract

AbstractOne of the challenges in achieving tunable and predictable C−H bond amidation via silver‐catalyzed nitrene transfer (NT) is the conformational flexibility and dynamic nature of many Ag(I) complexes. This fluxional behavior can make it difficult to obtain a clear understanding of the factors responsible for influencing the site‐selectivity of the amidation event. Mechanistic studies on related systems suggest that π⋅⋅⋅π and Ag⋅⋅⋅π interactions play important roles in altering the preference for nitrene transfer at sites adjacent to π systems, including benzylic, allylic, and propargylic C−H bonds. In this paper, we report a Ag(I) catalyst designed to improve the preference for reaction at benzylic, allylic, and propargylic C−H bonds over more electron‐rich tertiary alkyl C(sp3)−H bonds by enhancing non‐covalent interactions. Rigidifying a flexible tris(2‐pyridylmethyl)amine ligand scaffold by tying back the sp3 nitrogen into a piperidine ring strengthened non‐covalent interactions between the π‐containing substituents on the substrate and the pyridine arm of the catalyst and improved the site‐selectivity of the nitrene transfer event.