Organophotocatalytic oxidation of alcohols to carboxylic acids

Abstract

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 (O2•−) for the first oxidation step from alcohol to aldehyde and singlet oxygen (1O2) 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.