A Further Decrease in the Catalyst Loading for the Palladium-Catalyzed Direct Intramolecular Arylation of Amides and Sulfonamides

The direct arylation of N-substituted o-bromobenzanilides and benzenesulfonamides via C-H bond functionalization has been developed using very low catalyst loadings. This novel cost-effective and more sustainable method relies on a PCN-type palladium pincer complex as a highly active palladium source, providing a general and efficient access to phenanthridinones, biaryl sultams and related heterocyclic systems. The beneficial effect of water as cosolvent has been observed in this process, which is not seriously influenced by electronic effects at the arene moieties or sterically demanding substituents at the amide or sulfonamide nitrogen. In addition, a number of experiments (kinetic plot, poisoning assays, TEM, ESI) have been performed in order to understand the role of the employed palladium complex in this reaction.