Recent advances in C-H functionalization of 2 H -indazoles.

2 H -Indazoles are one class of the most important nitrogen-containing heterocyclic compounds. The 2 H -indazole motif is widely present in bioactive natural products and drug molecules that exhibit distinctive bioactivities. Therefore, much attention has been paid to access diverse 2 H -indazole derivatives. Among them, the late-stage functionalization of 2 H -indazoles via C-H activation is recognized as an efficient approach for increasing the complexity and diversity of 2 H -indazole derivatives. In this review, we summarized recent achievements in the late-stage functionalization of 2 H -indazoles, including the C3-functionalization of 2 H -indazoles through transition metal-catalyzed C-H activation or a radical pathway, transition metal-catalyzed ortho C2'-H functionalization of 2 H -indazoles and remote C-H functionalization at the benzene ring in 2 H -indazoles.