Site‐Selective Ortho/Ipso C‐H Difunctionalizations of Arenes using Thianthrene as a Leaving Group

Abstract

Site‐selective ortho/ipso C‐H difunctionalizations of aromatic compounds were designed to afford polyfunctionalized arenes including challenging 1,2,3,4‐tetrasubstituted ones (62 examples, up to 97% yields). To ensure the excellent regioselectivity of the process while keeping high efficiency, an original strategy based on a “C‐H thianthenation/Catellani‐type reaction” sequence was developed starting from simple arenes. Non‐prefunctionalized arenes were first regioselectively converted into the corresponding thianthrenium salts. Then, a palladium‐catalyzed, norbornene (NBE)‐mediated process allowed the synthesis of ipso‐olefinated/ortho‐alkylated polyfunctionalized arenes using a thianthrene as a leaving group (revisited Catellani reaction). Pleasingly, using a commercially available norbornene (NBE) and a unique catalytic system, synthetic challenges known for the Catellani reaction with aryl iodides were smoothly and successfully tackled with the “thianthrenium” approach. The protocol was robust (gram‐scale reaction) and was widely applied to the two‐fold functionalization of various arenes including bio‐active compounds. Moreover, a panel of olefins and alkyl halides as coupling partners was suitable. Pleasingly, the “thianthrenium” strategy was successfully further applied to the incorporation of other groups at the ipso (CN/alkyl/H, aryl) and ortho (alkyl, aryl, amine, thiol) positions, showcasing the generality of the process.