Photochemical C-H Arylation of Napthoquinones Using Eosin Y.

A visible-light-mediated C-H arylation of substituted 1,4-napthoquinones ( 1,4-SNQ ) and 1,2-napthoquinone ( 1,2-NQ ) with diazonium salt using a photocatalyst eosin Y at room temperature in a single step (isolated yield of ≥75%) is described in this report. The rate-determining step of the reaction is aryl radical generation, which was trapped by high-resolution mass spectrometry. Cost-effectiveness, operational simplicity, a short reaction time, high atom economy, and a good yield make this photoredox-mediated process a valuable alternative to the transition-metal (Fe, Cu, Pd, etc.)-catalyzed reaction.