Remote difunctionalization of 2-indazoles using Koser's reagents.

A new, efficient, and metal-free protocol has been developed for remote difunctionalization of unreactive C-H bonds at the benzene core of 2-indazole by employing Koser's reagents, which act as both sulfonyloxylating and iodinating agents under ambient air. The present methodology represents facile access to C-4-sulfonyloxylated and C-7-iodinated 2-indazole derivatives with high regioselectivity, wide functional group tolerance, and broad substrate scope in good to excellent yields. The formed 4,7 disubstituted 2-indazoles are the precursors of various C-4,7-functionalized 2-indazoles through simple transformations.