Additional Reductant-Free Visible-Light-Driven Davis–Beirut-Type Reaction: Access to Indazolin-3-ones from o -Nitrobenzaldimines

Abstract The reduction cyclization of o-nitrobenzaldimines is an important method for the construction of nitrogen-containing heterocycles. However, existing methods typically require additional reducing agents to reduce the nitro groups. Disclosed here is a direct photochemical oxygen atom transfer reaction in which bromoalkanes play a dual role that efficiently constructs a series of indazolin-3-one derivatives in moderate to good isolated yields. The developed protocol boasts a wide substrate scope and excellent step economy and does not require photocatalysts, transition metals, or reductants. Furthermore, scale-up synthesis and derivatization demonstrate the synthetic utility of the developed method.