Photo-oxygenation of 4H-pyran-4-thiones and 4H-thiopyran-4-thiones: reactivity and kinetic characterization

Abstract

Methylene Blue-sensitized photo-oxygenation of the 4H-pyran-4-thiones and 4H-thiopyran-4-thiones gives the corresponding ketones. The relative reactivity (β=k₁/k₂) of these thioketones to dye-sensitized oxygenation has been determined. The reactivity of the thioketones is the same or higher than that of tetramethylethylene. The quenching of the oxygenation by β-carotene suggests that the reactive species is singlet oxygen for the dyesensitized photo-oxygenation.