Weakening Bidentate Coordination Enables Pd-Catalyzed Annulation of 2-Iodobiphenyls with Methyl 3-Chloropyridine-2-carboxylates.

The palladium-catalyzed annulation of 2-iodobiphenyls with 3-chloropyridine-2-carboxylic acids provides a direct route to 1-azatriphenylenes, but the reaction suffers from low yields due to catalyst deactivation resulting from bidentate coordination of the pyridine-2-carboxylic acid to palladium. Simple esterification of the carboxylic acid to methyl 3-chloropyridine-2-carboxylate effectively weakens this coordination and restores catalytic activity, enabling the annulation to proceed in high yields. Furthermore, the resulting bay-region chloro-substituted 1-azatriphenylene isomers can undergo subsequent annulation with o-chlorobenzoic acids to afford 4-azadibenzo[fg,op]tetracenes.