Metal‐Free Nitration of Indazoles with <i>tert</i>‐Butyl Nitrile in Air to Prepare 3‐Nitroindazoles and 3‐Aminoindazoles

Comprehensive Summary A variety of 3‐nitroindazoles and 3‐aminoindazoles were prepared in good to excellent yields with high regioselectivity through TBN‐mediated nitration at the C3‐position of indazoles under the air conditions and sequential reduction. Mechanistic studies revealed that TBN played crucial roles to produce •NO 2 radical source in the presence of air conditions and C3‐nitration of indazoles was initiated by N1‐nitration and sequential migration of NO 2 group to C3‐position. Moreover, this method could be easily applied in the gram scalable synthesis of ibuprofen and ciprofibrate‐derived 3‐aminoindazoles. The present method highlights air as mild oxidant, metal‐free radical nitration of indazole, N—N bond formation and cleavage, and late‐stage modification of drugs.