Catalyst- and Oxidant-Free Electrochemical Halogenation Reactions of 2H-Indazoles with NaX (X=Cl, Br)

An environmentally friendly and highly efficient electrochemical method has been developed for halogenation of 2H-indazoles with cheap and commercially available NaX (X-Cl, Br) in the absence of metal catalysts and oxidants. Notably, this electrochemical process exhibits a broad substrate scope and high functional-group compatibility. A variety of 2H-indazoles are compatible with this transformation to give the corresponding products in modern to excellent yields. Also, this practical protocol avoids using external expensive supporting electrolytes. Last but not least, the procedure was carried out in an undivided cell at constant current condition under air atmosphere.