Trifunctionalization of Allenes via Cobalt-Catalyzed MHP-Assisted C–H Bond Functionalization and Molecular Oxygen Activation

We have developed an approach for the cobalt-catalyzed trifunctionalization of allenes to form versatile 3-acylquinolines in the presence of molecular oxygen with moderate to good yields in high regioselectivity. C–H bond functionalization of benzoic hydrazides assisted by the 2-(1′-methylhydrazinyl)­pyridine (MHP) acted as a key step in the cascade reaction. The reaction shows broad functional group tolerance of both allenes and hydrazides. Moreover, relevant experiments have been performed to probe the reaction mechanism.