Organophotocatalytic oxidation of alcohols to carboxylic acids

A sustainable photochemical protocol for the oxidation of alcohols to ketones and carboxylic acids has been developed by using 2,4,6-triphenylpyrylium tetrafluoroborate (TPPT) as organophotocatalyst and molecular oxygen as oxidant under visible light irradiation. The key reactive oxygen species, superoxide (O-2(center dot-)) for the first oxidation step from alcohol to aldehyde and singlet oxygen (O-1(2)) for the second oxidation step from aldehyde to carboxylic acid, were generated successfully by electron transfer and energy transfer pathways, respectively. A range of primary and secondary alcohols were converted to the corresponding carboxylic acids or ketones, and the optimized reaction conditions were applied to the synthesis of benzocoumarin.