Visible Light-Mediated Thiolation of Substituted 1,4-Naphthoquinones Using Eosin Y as a Photoredox Catalyst

In the presence of eosin Y, a visible light-induced one-step procedure (isolated yield of ≥75%) for thiolation of substituted 1,4-naphthoquinones using various aromatic and aliphatic thiols at room temperature is described herein. The rate-determining step of the reaction is thiyl radical generation, and the radical was characterized by high-resolution mass spectrometry. Cost effectiveness, operational simplicity, a short reaction time, high atom economy, and a very good yield make this photoredox-mediated process a useful alternative to the transition metal (e.g., Cu, Ag, and Pd)-catalyzed coupling reaction of quinones with thiols or disulfides.