Silylation of 2-indazoles by photoinduced hydrogen atom transfer catalysis.

A metal-free, visible-light-mediated C-H silylation of 2-indazoles with triphenylsilane has been developed employing 4CzIPN as a photocatalyst and triisopropylsilanethiol as a hydrogen atom transfer (HAT) reagent under aerobic reaction conditions. This method shows tolerance toward many functional groups and affords a variety of silylated indazoles at up to 89% yield. The experimental results suggest that the reaction progresses through a radical pathway.