Catalyst-free aerobic photooxidation of sensitive benzylic alcohols with chemoselectivity controlled using DMSO as the solvent

The drawbacks commonly observed in synthetic methods for alcohol oxidation often stem from the utilization of complex, toxic, hazardous, or waste-producing oxidants. When sensitive or complex substrates bearing several functional groups are to be transformed, the selectivity of oxidation becomes another significant challenge. Herein, a chemoselective and operationally simple catalyst-free and additive-free method is presented for the aerial oxidation of 1-phenylpropargyl and 1-phenylallyl alcohols to their corresponding ketones, requiring only a solvent and visible light irradiation. The crucial role of dimethylsulfoxide (DMSO) as the solvent lies in achieving high chemoselectivity. Singlet oxygen, whose formation is photosensitized by the substrate and the product, is captured by DMSO, thereby preventing the undesired over-oxidation that occurs in other solvents. The application of DMSO to protect the substrate against singlet oxygen represents a novel approach that is potentially applicable to other aerobic photocatalytic processes.醇氧化合成方法中普遍存在的弊端，通常源自所使用的氧化剂结构复杂、具有毒性与危害性且易产生废弃物。当需转化带有多种官能团的敏感或复杂底物时，氧化反应的选择性便成为另一项重大挑战。在此，我们报道一种兼具化学选择性且操作简便的无催化剂、无添加剂合成方法，可将1-苯基炔丙基醇与1-苯基烯丙基醇进行需氧氧化，转化为对应的酮类产物，该过程仅需溶剂与可见光辐照即可完成。二甲基亚砜（dimethylsulfoxide, DMSO）作为该反应的溶剂，其核心作用在于实现优异的化学选择性：由底物与产物光敏化生成的单线态氧（singlet oxygen）可被DMSO捕获，从而避免了在其他溶剂中易发生的非预期过度氧化。利用DMSO保护底物免受单线态氧攻击的策略，是一种全新的方法，有望推广应用于其他需氧光催化反应体系。