Controllable α- Or β-Functionalization of α-Diazoketones with Aromatic Amides via Cobalt-Catalyzed C-H Activation: A Regioselective Approach to Isoindolinones

Efficient procedures for the selective α- or β-functionalization of α-diazoketones with aromatic amides were developed by using a cobalt catalyst under ligand-free conditions. Normal α-functionalization of α-diazoketones was achieved via C(sp²)-H bond functionalization of aromatic amides in the presence of Co(acac)₂/TBHP. Interestingly, β-functionalization of α-diazoketones was realized with a Co(OAc)₂/AgOAc catalyst system. Further intramolecular cyclization afforded the desired isoindolinones in good to excellent yields.