Efficient and Site-Specific C–H Hydroxylation of Enones via a New Mechanism Useful for the Late-Stage Functionalization of Drugs and Natural Products

A mild and efficient method for the direct C(sp3)–H hydroxylation of enones in a site-specific way was developed via visible-light-induced hydrogen-atom transfer (HAT), which facilitates -hydroxylation of primary, secondary, and tertiary C–H bonds of different enones without involving metal and peroxide. The mechanistic study showed a new catalytic view, where Na2-eosin Y served as both the photocatalyst and the source of catalytic bromine radical species in the HAT-based catalytic cycle, and finally sacrificed itself completely by oxidative degradation to produce bromine radical and a major product phthalic anhydride in an environmentally friendly way. This scalable method was demonstrated by plenty of substrates to be extremely useful for the late-stage functionalization of drugs and natural products, and, in particular, has potential application in industry for large-scale production.