Ruthenium‐Catalyzed Regioselective Sulphonamidation of Benzo[ <i>b</i> ][1,4]oxazin‐2‐ones via Csp ² –H Functionalization Using Sulfonyl Azides

This study presents a novel ruthenium‐catalyzed method for the regioselective ortho ‐sulphonamidation of benzo[ b ][1,4]oxazin‐2‐ones. Utilizing sulfonyl azides, which release benign nitrogen gas as a byproduct, this approach achieves high yields and excellent ortho ‐selectivity in CH functionalization. The protocol exhibits a broad substrate scope, good functional group tolerance, and operational simplicity. Optimization studies and control experiments support a plausible reaction mechanism involving a ruthenium‐metallacycle intermediate. Gram‐scale synthesis demonstrates the practicality and potential of the method to access biologically relevant molecules, significantly expanding CH functionalization in heterocyclic chemistry.