Synthesis of Flavones from Chalcones Mediated by Copper(I) Iodide and Azides: Mechanistic Insights

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This article presents an alternative method for synthesizing flavones from chalcones using copper(I) iodide (CuI) and two azides-sodium azide and 4‑azidobenzenesulfonamide-as key reagents. The azides most likely undergo a Michael addition with chalcones to form 1,2,3‑triazoles, mediated by either stoichiometric or catalytic amounts of CuI. Interestingly, the expected 1,2,3‑triazoles were not obtained; instead, the forming 1,2,3‑triazoles intermediates appeared to undergo immediate intramolecular attack by the C2 hydroxy group of the A‑ring of chalcones, followed by elimination of the azides, ultimately yielding flavones. The yields and reaction rates were influenced by the varying amounts of CuI and azides employed. The key role of azides was not only to act as nucleophiles and leaving groups, but also to accelerate the reaction rate in the presence of CuI, in contrast to reactions conducted with CuI alone as previously reported. The unique mechanistic pathway was examined in detail.

Ce résumé expose les affirmations des auteurs. BNTIC ne l’interprète pas comme une validation indépendante des résultats.