9,10-Dihydroanthracene auto-photooxidation efficiently triggered photo-catalytic oxidation of organic compounds by molecular oxygen under visible light

The development of mild and efficient process for the selective oxidation of organic compounds by molecular oxygen (O-2) can be one of the key technologies for synthesizing oxygenates. This paper discloses an efficient and mild synthesis protocol for the O-2-involved ethylbenzene (EB) photooxidation triggered by 910-dihydroanthracene (DHA) auto- photooxidation in acetone under visible light illumination, which can achieve 87.7 EB conversion and 99.5 % acetylacetone (ACP) selectivity under ambient conditions. Also, 62.9 % EB conversion and 96.3 % ACP selectivity is obtained in air atmosphere. Furthermore, this protocol has a good adaptability for the photooxidation of other organic substrates such as tetrahydronaphthalene, diphenylmethane, toluene, cyclohexane, cyclohexene, alcohol, methylfuran and thioether to their corresponding oxygenates. A series of control and quenching tests, combined with EPR spectra, suggest that the photo-excited DHA can transfer its photo-electron to O-2 to yield a superoxide radical anion (O-2(center dot-)), then DHA is preferentially oxidized to anthraquinone (AQ) by the active O-2(center dot-) owing to its high reactivity. Finally, the in situ generated AQ as an active photo-catalyst can achieve the photooxidation of EB and other organic compounds by O-2. The present photoautoxidation protocol gives a good example for the O-2 -based selective oxidation of inert hydrocarbons under mild conditions.