Directing-group-free strategy for the iodine-mediated regioselective dichalcogenation of indolines: understanding the full catalytic cycles

An unprecedented metal-free-catalyzed regioselective direct dehydrogenation–dichalcogenation of indolines at the C3,5- or C2,3-positions via a directing-group-free strategy is described. This protocol presents remarkable features including high regioselectivity, high atom and step economy, environmental friendliness and broad substrate scope. Derivatization experiments revealed that the synthesized chalcoindoles had potential for further modification to afford other valuable functional molecules. Coupled with control experiments and density functional theory (DFT) studies, the reaction mechanism was elucidated to gain deeper insights into the observed regioselectivity. The present work not only reveals a highly selective synthetic route for the dichalcogenation of indolines, but also opens up a new avenue for the further development of valuable C–H functionalization in indole-benzene rings through the use of an oxidative dehydrogenation strategy. Furthermore, it contributes significantly to a deeper understanding of the regioselective C–H functionalization of indoles, which is of great importance for both fundamental studies and practical applications in the field of organic chemistry.