Photoinduced Electron Transfer in base-promoted Homolytic Aromatic Substitution and Related Systems. Is t-butoxide anion a key ingredient?

MARÍA E. BUDÉN

Lyon

Conferencia; Electron Transfer, Radicals Ions and Radical Chemistry ETRADCHEM; 2017

In the recent years, there is a booming of research in transition metal-free couplings of ArX to arenes to form biaryls. These reactions are triggered by alkali metal tert-butoxides in the presence of various additives via Base-promoted Homolytic Aromatic Substitution (BHAS). In 2008, the original report presented by Itami showed that KOtBu promoted the arylation of pyrazine and other electron‐poor arenes from ArI or ArBr, under elevated temperatures or MW irradiation. Later, different research groups have reported the construction of biaryls and stilbene derivatives from unactivated aromatic compounds by direct C-H activation of benzene or styrene using NaOtBu or KOtBu in the presence of a range of organic additives as ligands.2 As a consequence, the role of these organic additives in radical initiation attracted much research interest and different mechanisms have been proposed.Previously we reported on photoredox reactions for synthesis of biaryls (BHAS) and styrenes (Mizoroki−Heck-type) as a new alternative to induce these transformations at room temperature. Now, we propose a new alternative to induce these photoreactions, which involves dimsyl anion as a key ingredient. However, C-H functionalization of alkenes is produce without any solvent. Computational studies were performed to help to understand the initiation steps of these processes.