Site-Selective Late-Stage C-H Functionalization via Thianthrenium Salts

The high abundance of C-H bonds in organic molecules makes C-H functionalization a powerful approach to quickly increase the complexity of an organic molecule. However, the high abundance of C-H bonds also provides a challenge to C-H functionalization reactions: selectivity. While most C-H functionalization reactions produce mixtures of different products for most substrates, we have developed a highly selective method for aromatic C-H functionalization via sulfonium salts. The reaction does not require a certain directing group to be selective. The introduced functional group is a sulfonium group, which participates in various follow-up reactions such as palladium-catalyzed cross-coupling reactions and photoredox catalysis. Here we discuss our pathway to develop the reaction as well as its scope and utility.