Aplicação de iodo hipervalente na selenilação de arenos ativados.

Abstract

The development of environmentally friendly methods has been one of the most expanding areas in scientific research in recent years. The development of new methodologies, modifying techniques already known and used in the field, is a challenge for researchers. Therefore, this work aims at a method to functionalize sp2 carbon atoms attached to activated aromatic rings, using procedures that fit the sustainable foundations of green chemistry. Initially, the optimization of the method was carried out, using diphenyl diselenide and N,N-dimethylaniline as reference reagents, with several modifications in time, temperature and solvents. Thus, the reaction condition used 0.5 molar equivalent of PhICl2 as oxidizing agent, 1,4-Dioxane as solvent, at room temperature, in open atmosphere, for 30 minutes. This led to N,N-Dimethyl-4-(phenylselenyl)aniline in an isolated yield of 92%. Then, tests were conducted with different diselenides, in order to evaluate the efficiency of the methodology. The regioselectivity is seen from the greater coupling occurring in the –para position to anilines, and –ortho, when in the occurrence of substituents that weaken the ring resonance, or that present a steric effect. Furthermore, based on literature studies and control experiments, a mechanism was proposed, where there is the formation of the electrophilic species RYCl in situ, indicating an ionic pathway. Thus, it was possible to develop an efficient and more sustainable synthetic route for the chalcogenation of C(sp2)-H.