Citric Acid Mediated One-pot Regioselective Synthesis of N-Alkylated Indazoles: an Efficient Green Strategy

Citric acid mediated green synthetic route has been demonstrated for the regioselective synthesis of N-alkylated indazoles in good to excellent isolated yields ( ~ 78-96%) from readily available starting materials 2-methylanilines (1), NaNO 2 (2) and ethyl chloroacetate (3) via diazotization, intra molecular cyclization and followed by N-alkylation in the presence of 1:1 ratio of ethanol and water in one-pot.Notably, if the substrate (1) contains -NO 2 group and is reduced to -NH 2 in the presence of Fe, CaCl 2 in the same pot at 60-65°C for 30-40 min.The remarkable advantages of this method include cleaner reaction profile, easy to perform, high yields of products and simple work-up procedure.Besides, the reaction is step-and atom-economic and is carried out in green catalytic medium.