Harnessing Vinyl Acetate as an Acetylene Equivalent in Redox-Neutral CpCo(III)-Catalyzed C–H Activation/Annulation for the Synthesis of Isoquinolones and Pyridones

We have developed Cp*Co­(III)-catalyzed redox-neutral synthesis of 3,4-unsubstituted isoquinoline 1­(2H)-ones at ambient temperature using N-chloroamides as a starting material. The reaction utilizes vinyl acetate as an inexpensive and benign acetylene surrogate. The N–Cl bond of the N-chlorobenzamides plays the role of an internal oxidant and hence precludes the need for an external oxidant. The reaction works with a wide range of substrates having various functional groups and a substrate containing a heterocyclic ring. Notably, the reaction is extended to the N-chloroacrylamides in which vinylic C–H activation occurs to furnish the 2-pyridone derivatives. Preliminary mechanistic studies were also conducted to shed light on the mechanism of this reaction.