Palladium-Catalyzed Directed C(sp ³ )–H Activation/Lactonization Cascade of 2-Acyl <i>N</i> -Heteroarenes with 2-Halobenzoic Acids: A Route to Substituted Isocoumarins

A palladium-catalyzed, <i>N</i>-directed C(sp³)-H functionalization and intramolecular lactonization of 2-acyl <i>N</i>-heteroarenes with 2-halobenzoic acids is reported, providing an efficient synthetic route to access <i>N</i>-heteroarene-substituted isocoumarins. The protocol demonstrates a broad substrate scope and chemoselectivity and is tolerant of diverse <i>N</i>-heteroarene and benzoic acid derivatives. The observed inverse kinetic isotope effect is likely a secondary isotope effect resulting from the sp² to sp³ rehybridization of the acyl methyl carbon, to which the proton or deuteron is attached.