Electrosynthesis of 1H- and 2H-indazoles by reduction of o -nitrobenzylamines, a versatile and sustainable access

Indazoles represent an important pharmacologically active class of compounds. However, reliable and sustainable pathways from simple substrates remain scarce. We report an easily applicable and sustainable electrochemical synthesis of various 1H- and 2H-indazoles via direct reduction of o-nitrobenzylamines, avoiding stoichiometric reagents and elevated temperatures. The protocol enables access to 50 distinct structures with isolated yields up to 96% and a broad tolerance for functional groups and heterocycles. Additionally, we demonstrate electrochemical post-functionalization, access to APIs and their precursors, as well as robust scalability.