Visible-Light-Triggered Radical-Addition/Ring-Opening Cascade Reactions of 2-Indazoles to Access -Alkoxycarbonylated Azobenzenes.

A series of asymmetric azobenzenes have been synthesized by radical-addition/ring-opening cascade reactions from 2-indazole in the presence of PIFA and alcohols under blue light irradiation and nitrogen protection. Furthermore, a wide range of functional groups were tolerated and the corresponding products were obtained in 30% to 95% isolated yields. The protocol is characterized by its visible-light initiation, avoidance of metals and photocatalysts, mild reaction conditions, and may find potential use in materials science and medicinal chemistry.