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Article Dans Une Revue Organic & Biomolecular Chemistry Année : 2021

Understanding Cu( ii )-based systems for C(sp 3 )–H bond functionalization: insights into the synthesis of aza-heterocycles

Résumé

Herein we report the synthesis of imidazo[1,5-a]pyridine heterocycles via a Cu(II)-mediated functionalization of α′-C(sp3)–H bonds of pyridinylaldimines and subsequent cyclization. This strategy exploits the inherent directing ability of heteroleptic aldimine and pyridine groups in the substrate yielding the C–H functionalization of α′-methylene groups in a regioselective fashion over distant methyl or methylene groups in β or γ positions. The observed correlation between the nature of the anionic ligands (halide vs. carboxylate) bonded to copper and the chemoselectivity of the C(sp3)–H activation process points to a concerted metalation–deprotonation pathway prior to cyclization to furnish the corresponding imidazo[1,5-a]pyridine derivative. This copper-mediated C(sp3)–H bond functionalization reaction works for a variety of substrates incorporating linear alkyl chains (from 3 to 12 carbon atoms), and good functional group tolerance (aryl, ether and ester groups). Cu-Catalyzed C(sp2)–H cyanation on the imidazole ring can then take place selectively under oxidative conditions.
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hal-03806424 , version 1 (07-10-2022)

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Marc Camats, Isabelle Favier, Sonia Mallet-Ladeira, Daniel Pla, Montserrat Gómez. Understanding Cu( ii )-based systems for C(sp 3 )–H bond functionalization: insights into the synthesis of aza-heterocycles. Organic & Biomolecular Chemistry, 2021, 20 (1), pp.219-227. ⟨10.1039/D1OB02118D⟩. ⟨hal-03806424⟩
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