Copper-Catalyzed Intramolecular Benzylic C–H Amination for the Synthesis of Isoindolinones

A copper-catalyzed intramolecular amination occurs at the benzylic C–H of 2-methylbenzamides to deliver the corresponding isoindolinones of great interest in medicinal chemistry. The mild and abundant MnO2 works well as a terminal oxidant, and the reaction proceeds smoothly under potentially explosive organic peroxide-free conditions. Additionally, the directing-group-dependent divergent mechanisms are proposed: 8-aminoquinoline-containing benzamides include a Cu-mediated organometallic pathway whereas an aminyl radical-promoted Hofmann–Loffler–Freytag (HLF)-type mechanism can be operative in the case of N-naphthyl-substituted substrates.