Rhodium-Catalyzed C-H Activation/Annulation of N‑Chlorobenzamide Derivatives with Alkynes.

Highly efficient synthesis of isoquinolones is achieved by a Rh-(III)-catalyzed C-H activation/annulation of N-chlorobenzamide derivatives with alkynes. This transformation leverages the N-Cl moiety as a highly effective internal oxidant, enabling the reaction to proceed smoothly under mild conditions and delivering the target products in excellent yields (up to 98% yield). Control experiments further reveal the superior oxidizing ability of the N-Cl benzamide relative to its N-OMe and N-OPiv analogues. Notably, the reaction proceeds with 85% yield even at an exceptionally low catalyst loading of 0.05 mol %.