Regioselective C3–C4 difunctionalization of 4-bromocoumarins <i>via</i> Pd/norbornene catalysis

The difunctionalization of arenes <i>via</i> Catellani-type reactions has predominantly relied on aryl iodides and has faced persistent limitations with dual bromide systems, particularly with benzyl bromides, which are susceptible to oxidation reactions. Herein, we present a Pd-catalyzed/norbornene-mediated vicinal difunctionalization of 4-bromocoumarins <i>via</i> sequential alkylation and vinylation using dual bromide partners-a longstanding challenge in Catellani chemistry.