Rhodium‐Catalyzed Cascade Annulation of <i>N</i> ‐Nitrosoanilines With Trifluoromethyl‐Imidoyl Sulfoxonium Ylides for the Synthesis of Trifluoromethyl‐Functionalized Indazole <i>N</i> ‐Oxides

Herein, an efficient and mild methodology was developed to synthesize trifluoromethyl‐functionalized indazole N ‐oxides with diverse substitutes via Rh(III)‐catalyzed C–H activation/[4 + 1] annulation between N ‐nitrosoanilines and trifluoromethyl‐imidoyl sulfoxonium ylides at room temperature under air atmosphere. The manuscript represents the first example of synthesis of indazole N ‐oxides via C–H activation at ambient temperature. The cascade reaction involves imidoylmethylation, tautomerization, and C–N bond formation, exhibiting mild reaction conditions, excellent substrate scalability, and high functional groups tolerance. Additionally, as the directing group, N ‐nitroso can be transformed to desired indazole scaffold after coupling, improving atom economy significantly. The gram‐scale experiment also highlighted its potential for large‐scale production and practical applications.