Harnessing the Excited‐State Reactivity of o ‐Nitrobenzyl Alcohols for the Rapid Synthesis of N ‐Substituted 2 H ‐Indazoles

2 H ‐Indazole scaffolds represent privileged structural motifs prevalent in a wide range of bioactive compounds and pharmaceutical agents. Despite their significance, conventional synthetic approaches to 2 H ‐indazole derivatives often suffer from limitations such as harsh reaction conditions, the use of expensive or toxic catalysts, and multistep procedures. To address these challenges, we report a cost‐effective, environmentally benign, and one‐pot strategy for the synthesis of biologically and synthetically valuable 3‐arylamino‐2‐aryl‐2 H ‐indazoles. This method employs readily available o ‐nitrobenzyl alcohols as key building blocks and utilizes a Lewis acid iron salt as a catalyst under visible light irradiation, harnessing the excited‐state reactivity of the substrates. The transformation proceeds efficiently without the need for precious metal catalysts, external oxidants, or additives and operates under mild and sustainable conditions. The protocol enables the construction of structurally complex 2 H ‐indazoles, including those embedded in medium‐sized rings. Notably, the synthesized 3‐arylamino‐2‐aryl‐2 H ‐indazoles exhibit a selective fluorescence quenching response toward hypochlorite, highlighting their potential as an effective probe for ClO − detection.