Palladium‐Catalyzed Oxidative Cyclocarbonylation of Isoquinolones with CO via C−H/N−H Bond Cleavage: Easy Access to Isoindolo[2,1‐ b ]isoquinoline‐5,7‐dione Derivatives

An efficient and practical synthesis of isoindolo[2,1‐ b ]isoquinoline‐5,7‐diones through Pd‐catalyzed C−H activation/carbonylative annulation of isoquinolones with CO (1 atm) is presented. Deuterium‐labeling experiments revealed that the aryl C( sp 2 )−H bond activation might be the rate‐determining step. More interestingly, the title compounds could also be prepared directly from the cascade reaction of N ‐methoxy benzamides and internal alkynes, as the precursors of isoquinolones, under an atmospheric pressure of carbon monoxide through a Rh/Pd relay catalysis in a user‐friendly manner.