INFIQC   05475
INSTITUTO DE INVESTIGACIONES EN FISICO- QUIMICA DE CORDOBA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Initiation of Photoredox C-H Functionalization Reactions
Autor/es:
MARÍA E. BUDÉN; MARCELO PUIATTI; JAVIER I. BARDAGÍ; ADRIANA B. PIERINI; ROBERTO A. ROSSI.
Lugar:
Carlos Paz
Reunión:
Congreso; 13º Conferencia Latinoamericana de Físico-química Orgánica (CLAFQO); 2015
Resumen:
Recent papers report transition metal-free couplings of haloarenes to arenes to form biaryls,triggered by alkali metal tert-butoxides in the presence of various additives via base-promoted Homolytic Aromatic Substitution (BHAS). These reactions proceed through radical intermediates,but the origin of the radicals remains unclear. Recently, Murphy et al. showed that the reactivity of some of these additives (e.g. amino acids, 1,2-diols, etc) could be explained by the in situ formation of organic electron donors. In the absence of additives, the coupling reactions are still successful, and in those cases benzyne is proposed to play a crucial role in the initiation process. It is know that KOtBu could initiate photosubstitution reaction with ArX. Moreover, we reported the synthesis of biaryls and E-stilbenes catalyzed only by KOtBu and light.However, there are not reported photoredox reactions with alkyl halides as substrates in BHAS and how is the initiation step in those photoactivation reactions. In the present work, we proposed a new alternative to induce those photoreactions that involves dimsyl anion when DMSO is used as a solvent.In the photostimulated reaction (350 nm, 400 W lamps), 1-iodoadamantane reactedwith benzene (5 equiv) and KOtBu or NaH (3 equiv) in DMSO to give 76-77% yield of 1-Ad-Ph. Although other solvents were also screened, AdI was recovered quantitatively. The formation of radicals and radical anions were supported by experiments performed in the presence of radical scavengers and a good electron acceptors such as m-dinitrobenzene which inhibited the reactions. Moreover, the reaction using blue-LED (455 nm, 3W) afforded the substitution product in 85% yield.Also, DMSO was necessary when ArI were used in BHAS. However, C-Hfunctionalization of alkenes are produce without any solvent. In order to explain how is the initiation step in all C-H functionalization computational studies were performed.