t-BuOOH/TiO₂ Photocatalytic System as a Convenient Peroxyl Radical Source at Room Temperature under Visible Light and Its Application for the CH-Peroxidation of Barbituric Acids

TiO2 is one of the most promising heterogeneous photoredox catalysts employed in oxidative pollutant destruction, CO2 reduction, water splitting, disinfection, solar cell design and organic synthesis. Due to the wide bandgap of TiO2, visible light energy is not sufficient for its activation, and electron/hole pairs generated upon UV irradiation demonstrate limited selectivity for application in organic synthesis. Thus, the development of TiO2-based catalytic systems activated by visible light is highly attractive. In the present work we demonstrate the generation of t-BuOO center dot radicals from tert-butylhydroperoxide catalyzed using commercially available unmodified TiO2 under visible light. This finding was used for the highly selective CH-peroxidation of barbituric acids, which contrasts with the behavior of the known TiO2/H2O2/UV photocatalytic system used for deep oxidation of organic pollutants.