Electrochemistry Broadens the Scope of Flavin Photocatalysis: Photoelectrocatalytic Oxidation of Unactivated Alcohols.

Riboflavin-derived photocatalysts have been extensively studied in the context of alcohol oxidation. However, to date, the scope of this catalytic methodology has been limited to benzyl alcohols. In this work, we gained further mechanistic understanding of flavin-catalyzed oxidation reactions in the absence or presence of thiourea as a cocatalyst. The mechanistic insights enabled us to develop an electrochemically driven photochemical oxidation of primary and secondary aliphatic alcohols using a pair of flavin and dialkylthiourea catalysts. Electrochemistry makes it possible to avoid using O2 oxidant and generating H2O2 byproduct, both of which oxidatively degrade thiourea under the reaction conditions. This modification unlocks a new mechanistic pathway in which the oxidation of unactivated alcohols is achieved via thiyl radical-mediated hydrogen-atom abstraction.

核黄素衍生的光催化剂在醇氧化方面已被广泛研究。然而，到目前为止，这种催化方法的适用范围仅限于苄醇。在这项工作中，我们在有或没有硫脲作为助催化剂的情况下，对黄素催化的氧化反应有了更深入的机理理解。这些机理见解使我们能够利用一对黄素和二烷基硫脲催化剂开发一种电化学驱动的伯醇和仲脂肪醇的光化学氧化方法。电化学使得在反应条件下避免使用氧气氧化剂以及产生过氧化氢副产物成为可能，因为在该反应条件下氧气和过氧化氢都会氧化降解硫脲。这种改进开启了一种新的机理途径，即通过硫自由基介导的氢原子抽取来实现未活化醇的氧化。