Ir/Ni Metallaphotoredox Catalysis for the C(sp 3 )-H Bond α-Arylation and Alkylation of N-Alkyl N-Heterocycles
Résumé
In this work, we report a regioselective C(sp 3 )-H bond α-arylation and alkylation of N-alkyl heterocycles (carbazoles, indoles and indazoles) using a Ir/Ni metallaphotoredox catalysis. This approach enables the direct functionalization of unactivated C(sp 3 )-H bonds at the α-position of nitrogen heterocycles, offering an efficient alternative to traditional SN2 methods and providing complementary regioselectivity to transition metal catalysis, which often results in C(sp 2 )-H bond arylation. The reaction employs [Ir(dF(CF3)ppy)2(dtbbpy)][PF6] as the photocatalyst and NiCl2(dtbbpy) as the nickel source, facilitating single-electron transfer (SET) to promote radical generation and organometallic elementary cross-coupling steps. The methodology allows the use of diverse aryl chlorides and alkenes, demonstrating broad substrate scope and high functional group tolerance. Mechanistic investigations, including radical trapping and and Stern-Volmer experiments, support a photocatalytic radical pathway. This new metallaphotoredox protocol presents a robust and atomeconomical route to synthesizing valuable N-alkyl-N-aryl heterocycles.
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