Photooxygenations of 1-naphthols: an environmentally friendly access to 1,4-naphthoquinones

Dye sensitized photooxygenations of 1-naphthols were investigated with soluble and solid-supported sensitizers and moderate to excellent yields of the corresponding 1,4-naphthoquinones were achieved in relatively short irradiation times. The mild and environmentally friendly reaction conditions made this application particularly attractive for ‘Green Photochemistry’. Consequently, the photooxygenation of 1,5-dihydroxynaphthalene was studied with non-concentrated and moderately concentrated sunlight and 5-hydroxy-1,4-naphthoquinone (Juglone) was obtained in yields up to 71%.