Photoredox Halogenation of Quinolones: Dual Role of Halo-fluorescein Dyes

An efficient C-3 halogenation of quinolin-4-ones is reported with halogenated fluorescein dyes which serve both as halogen source and photocatalyst. The reaction shows broad substrate scope and gives good to excellent yield of the C-3 brominated/iodinated quinolones with Eosin Y/Rose Bengal in green light under ambient conditions. The mechanistic investigations suggest a radical pathway involving oxidative dehalogenation of the dye in presence of air.