Direct radical alkylation and acylation of 2H-indazoles using substituted Hantzsch esters as radical reservoirs

Abstract

A platform approach for the direct synthesis of 3-substituted 2H-indazole derivatives has been developed using a Ag(I)/Na₂S₂O₈ system. This regioselective alkylation/acylation protocol operates under mild conditions, tolerates a wide range of structural moieties and delivers versatile 2H-indazole derivatives with high efficiency. The gram-scale reaction and the application to the synthesis of bioactive molecules further demonstrate the utility of our protocol.