SmI2-mediated enantioselective reductive dearomatization of non-activated arenes

Arenes are fundamental feedstocks for many chemical processes within organic synthesis. The dearomatization of arenes, especially non-activated benzene derivatives, has long been recognized as an important synthetic transformation. However, developing enantioselective variants of these dearomative reactions remains a challenge due to the inherent stability of benzene derivatives. Here we report the development of a samarium diiodide (SmI2)-mediated enantioselective reductive dearomatization of non-activated benzene derivatives. The use of chiral tridentate aminodiol ligand forms a chiral samarium complex, mediating the intramolecular addition of a ketyl radical onto one of the two enantiotopic arene rings in a stereoselective fashion. The scope of the process is displayed through the synthesis of a range of dearomatized bicycles bearing three stereogenic centres, in good yield and stereocontrol. Scale-up of the process and further reductive and olefination transformations of the bicyclic products showed the synthetic utility of the SmI2-mediated process.