Light-promoted oxidation of aldehydes to carboxylic acids under aerobic and photocatalyst-free conditions

Abstract

The development of green and sustainable methods for the conversion of aldehydes to carboxylic acids is of high academic and industrial interest. We demonstrate herein a practical and efficient light-promoted oxidation of aldehydes, utilising atmospheric oxygen as the sole oxidant. The transformation is promoted by either sunlight or LED 370 nm irradiation, without the use of a catalyst. A solvent mixture of acetone and water proved to be the most effective solvent medium. A wide range of aliphatic or aromatic aldehydes were successfully employed, providing the corresponding carboxylic acids in high to excellent yields. A mechanism was proposed based on direct infusion-high resolution mass spectrometry (DI-HRMS) studies, suggesting a solvent-assisted oxidative transformation. The method is green, sustainable and operationally simple under very mild conditions.