Catalytic Photoredox C−H Arylation of 4‑Oxo‑4H‑pyrido[1,2‑a]pyrimidine-3-diazonium Tetrafluoroborates and Related Heteroaryl Diazonium Salts

Irradiation of mixtures of title diazonium salts and heteroarenes with green light (510 nm) in the presence of eosin Y disodium salt (EY-Na₂) as a photocatalyst furnished the corresponding arylation products in 8−63% yields. The proposed photocatalytic cycle is analogous to that proposed previously for closely related photoredox C−H arylations with aryl diazonium salts as aryl radical sources. This method has a broad substrate scope and represents a metal-free alternative for the synthesis of 3-heteroaryl-substituted 4H-quinolizin-4-ones and azino- and azolo-fused pyrimidones with a bridgehead nitrogen atom.

Read article: J. Org. Chem., 2023, 88, 13934