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Direct C–H photoarylation of diazines using aryldiazonium salts and visible-light

2020; Royal Society of Chemistry; Volume: 10; Issue: 52 Linguagem: Inglês

10.1039/d0ra06876d

2046-2069

Rodrigo C. Silva, Lucas F. Villela, Timothy J. Brocksom, Kléber T. de Oliveira,

Sulfur-Based Synthesis Techniques

In this study, direct C-H photoarylation of pyrazine with aryldiazonium salts under visible-light irradiation (blue-LEDs) is described, and additional examples including photoarylations of pyrimidine and pyridazine are also covered. The corresponding aryl-diazines were prepared in yields up to 84% only by mixing and irradiating the reaction with no need for an additional photocatalyst. We demonstrate the efficacy of this protocol by the scope with electron-donor, -neutral, and -withdrawing groups attached at the ortho, meta, and para positions of the aryldiazonium salts; the results are better than those reported for ruthenium-complex mediated photoarylations. Additionally, we demonstrate the robustness of this methodology with a 5 mmol scaled-up experiment. Mechanistic studies were carried out giving support to the proposal of a photocatalyzed approach by an electron donor-acceptor (EDA) complex, also highlighting the crucial role that solvents play in the formation of the EDA complex.