Co(III)-Catalyzed Coupling-Cyclization of Aryl C-H Bonds with alpha-Diazoketones Involving Wolff Rearrangement

An unusual cobalt(III)-catalyzed cross-coupling/cyclization of aryl C-H bonds of N-nitrosoanilines with alpha-diazo-beta-ketoesters has been achieved. This protocol features a unique combination of Csp2-H activation/Wolff rearrangement process, allowing for the rapid assembly of quaternary 2-oxindoles. The empirical evidence and density functional theory (DFT) calculations reveal the trapping process of transient acceptor ketene intermediates by cobalt metallocycles.