{Reference Type}: Journal Article
{Title}: An Investigation of N-Hydroxyphthalimide Catalyzed Aerobic Oxidation of Toluene without Metal Ions in Liquid Phase: Effect of Solvents and Phase Transfer Catalysts.
{Author}: Shi G;Dong L;Feng Y;
{Journal}: Molecules
{Volume}: 29
{Issue}: 13
{Year}: 2024 Jun 27
{Factor}: 4.927
{DOI}: 10.3390/molecules29133066
{Abstract}: The selective oxidation of toluene to yield value-added oxygenates, such as benzyl alcohol, benzaldehyde, and benzoic acid, via dioxygen presents a chlorine-free approach under benign conditions. Metal-free catalytic processes are preferred to avoid metal ion contamination. In this study, we employed N-hydroxyphthalimide (NHPI) as a catalyst for the aerobic oxidation of toluene to its oxygenated derivatives. The choice of solvent exerted a significant impact on the catalytic activity and selectivity of the catalyst NHPI at reaction temperatures exceeding 70 °C. Notably, hexafluoroisopropanol substantially enhanced the selective production of benzaldehyde. Furthermore, we identified didecyl dimethyl ammonium bromide, featuring two symmetrical long hydrophobic chains, as a potent enhancer of NHPI for the solvent-free aerobic oxidation of toluene. This effect is ascribed to its unique symmetrical structure, extraction capabilities, and resistance to thermal and acid/base conditions. Based on the product distribution and control experiments, we proposed a plausible reaction mechanism. These findings may inform the industrial synthesis of oxygenated derivatives from toluene.