Regiodivergent Pd-Catalyzed Annulation of Coumarins: Directing-Group-Controlled Coumarin-Fused N-Heterocycles

A unified, palladium-catalyzed annulation of 4-bromocoumarins with diphenylacetylene, enabling site-selective access to two distinct classes of coumarin-fused N-heterocycles, is developed. The coordinating nitrogen-based partner precisely dictates the site of activation: aniline directs peri- (C5-H) activation, while 2-aminopyridine promotes vinylic (C3-H) activation. Both transformations proceed efficiently under air without the need for stoichiometric oxidants or preinstalled directing groups. The method tolerates a broad range of anilines, aminopyridines, and internal alkynes, affording annulated products in good to excellent yields. In this system, the directing group solely dictates Pd-catalyzed C5-H vs C3-H selectivity via 5-/6-membered intermediates. This is the first directing-group-controlled regiodivergent Pd-catalyzed C-H annulation of coumarins, enabling complete C5/C3 selectivity switching in heteroaromatics.