PDF(Pubmed)
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.
摘要：
甲苯的选择性氧化以产生增值的含氧化合物，如苯甲醇，苯甲醛,还有苯甲酸,在良性条件下，通过双氧提供无氯方法。不含金属的催化方法是优选的,以避免金属离子污染。在这项研究中,我们使用N-羟基邻苯二甲酰亚胺（NHPI）作为催化剂，将甲苯有氧氧化为其含氧衍生物。溶剂的选择对催化剂NHPI在超过70°C的反应温度下的催化活性和选择性产生显著影响。值得注意的是,六氟异丙醇大大提高了苯甲醛的选择性生产。此外，我们确定了二癸基二甲基溴化铵，具有两个对称的长疏水链，作为NHPI的有效增强剂，用于甲苯的无溶剂好氧氧化。这种效果归因于其独特的对称结构，提取能力，和耐热和耐酸/碱条件。根据产品分布和控制实验，我们提出了一个合理的反应机理。这些发现可以为从甲苯工业合成含氧衍生物提供信息。
