Regioselective C3-H trifluoromethylation of 2H-indazole under transition-metal-free photoredox catalysis

Trifluoromethyl-substituted heteroarenes are biologically active compounds and useful building blocks. In this sequence, we have developed a visible-light-promoted regioselective C3–H trifluoromethylation of 2H-indazole under metal-free conditions, which proceeds via a radical mechanism. The combination of photocatalysis and hypervalent iodine reagent provides a practical approach to a library of trifluoromethylated indazoles in 35–83% yields.