Counterion Effects Enable Divergent Pd‐Catalyzed Carbonylative Cyclization of Amide‐Tethered o‐Alkynylphenols

The catalytic carbonylation of alkynes is a powerful route to heteroaromatic scaffolds, yet achieving regioselectivity remains challenging. Herein, we report a divergent carbonylative cyclization of 2‐alkynylphenol derivatives that affords either coumarins (6‐ endo‐dig ) or 2‐coumaranones (5‐ exo‐dig ) by tuning the palladium‐based catalytic system. Pd(OAc) 2 in combination with TFA favored coumarins formation with high yield and selectivity (>15:1), whereas electron‐deficient species such as Pd(MeCN) 4 (BF 4 ) 2 promoted 2‐coumaranones with up to 84% yield and >25:1 selectivity. While many approaches exploit ligand design to steer selectivity, these results highlight counterion effects as a powerful tool to control regioselectivity in palladium‐catalyzed carbonylative cyclization, expanding the utility of alkyne carbonylation for the synthesis of biologically relevant heterocycles.