Catalyst-free Regioselective Photoarylation of 2-Aryl-2H-indazoles by Carbon-Halogen Bond Activation

Abstract

A photocatalyst-free visible-light induced regioselective arylation of 2-aryl-2H-indazoles has been developed for the first time to produce 3,2-diaryl-2H-indazoles in good to excellent yields. In this transformation, potassium tert-butoxide acts as an activator of C-X bond and also as a scavenger of in situ generated HI in the reaction. This method exhibits high functional group tolerance with a wide substrate scope and it has been successfully applied to the synthesis of liver X receptor agonist and also for fluorescent probe. This is a first report on the photoarylation of 2-arylindazoles at 3-position with aryl iodides under catalyst free conditions.