Origins of Catalyst-Controlled Selectivity in Ag-Catalyzed Regiodivergent C-H Amination.

Abstract

Ag-catalyzed nitrene transfer (NT) converts C-H bonds into valuable C-N bonds. These reactions offer a promising strategy for catalyst-controlled regiodivergent functionalization of different types of reactive C-H bonds, as the regioselectivity is tunable by varying the steric and electronic environments around the Ag nitrene, as well as the identity of the nitrene precursors and the tether length. Therefore, a unified understanding of how these individual factors affect the regioselectivity is key to the rational design of highly selective and regiodivergent C-H amination reactions. Herein, we report a computational study of various Ag-catalyzed NT reactions that indicates a concerted H-atom transfer (HAT)/C-N bond formation mechanism. A detailed analysis was carried out on the effects of the C-H bond dissociation enthalpy (BDE), charge transfer, ligand-substrate steric repulsions, and transition state ring strain on the stability of the C-H insertion transition states with different Ag nitrene complexes. The ancillary ligands on the Ag and the nitrene precursor identity both affect transition state geometries to furnish differing sensitivities to the BDE, tether length, and electronic effects of the reactive C-H bonds. Based on our understanding of the dominant factors that control selectivity, we established a rational catalyst and precursor selection approach for regiodivergent amination of diverse C-H bonds. The computationally predicted regiodivergent amination of β- and γ-C-H bonds of aliphatic alcohol derivatives was validated by experimental studies.