Copper-Mediated C4–H Sulfonylation of Indoles via a Transient Directing Group Strategy

The synthesis of C4-decorated indoles is of great significance in the construction of bioactive and functional molecules. Currently, the late-stage C4–H functionalization of indole scaffolds largely relies on toxic and expensive 4d/5d transition metal catalysts and preinstalled directing groups, which considerably limits their practical applications. In this work, we report a copper-mediated C4–H sulfonylation of indoles via a transient directing group strategy. This method features high atom- and step-economy, outstanding regioselectivity, and broad functional group compatibility, providing a novel and practical solution for the C4-functionalization of indole cores.