Visible-Light-Driven Chalcogenocyclization of Naphthoquinones under Sustainable Conditions

Naphthoquinones are redox-active scaffolds known for their ability to generate reactive oxygen species (ROS)
and for their broad biological and photophysical applications. Chalcogen-containing compounds, particularly
those bearing sulfur, selenium, and tellurium, further enhance these properties through modulation of
electronic and redox behavior. Herein, we report a sustainable visible-light-assisted methodology for the
selective cyclization and chalcogen functionalization of naphthoquinones under mild conditions. Using juglone
and diphenyl diselenide as model substrates, reaction optimization under blue LED irradiation in the presence
of SnCl2·2H2O afforded chalcogen-naphthoquinones in yields of up to 94% (3a-h, 4a-c and 5a-c). The protocol
was successfully extended to lawsone and lapachol, enabling the synthesis of structurally diverse sulfur-,
selenium-, and tellurium-containing derivatives. Mechanistic studies, including light on/off experiments,
supported a photoinduced chalcogen-radical pathway. Overall, this methodology provides an efficient,
versatile, and sustainable approach for accessing chalcogen-functionalized naphthoquinones with broad
synthetic potential.