德国明斯特大学Studer Armido团队报道了光催化膦介导的水活化用于自由基加氢。相关研究成果于2023年6月28日发表于国际顶尖学术期刊《自然》。

水的化学活化将使地球上丰富的资源转化为增值化合物，这是能源研究中一个非常感兴趣的话题。

该文中，研究人员展示了在温和条件下用光催化膦介导的自由基过程活化水。该反应产生无金属的PR₃–H₂O自由基阳离子中间体，其中两个氢原子通过两个O–H键的顺序异裂解（H⁺）和均裂解（H）裂解在随后的化学转化中使用。PR₃–OH自由基中间体提供了一个理想的平台，可以模拟“自由”氢原子的反应性，并可以直接转移到闭壳π系统，如活性烯烃、未活性烯烃、萘和喹啉衍生物。

生成的H加合物C自由基最终被硫醇助催化剂还原，导致π体系的整体转移氢化，水的两个H原子最终进入产物中。热力学驱动力是氧化膦副产物中形成的强P=O键。实验机理研究和密度泛函理论计算表明，PR₃–OH中间体的氢原子转移是自由基加氢过程中的关键步骤。

附：英文原文

Title: Photocatalytic phosphine-mediated water activation for radical hydrogenation

Author: Zhang, Jingjing, Mck-Lichtenfeld, Christian, Studer, Armido

Issue&Volume: 2023-06-28

Abstract: The chemical activation of water would allow this earth-abundant resource to be transferred into value-added compounds, and is a topic of keen interest in energy research1,2. Here, we demonstrate water activation with a photocatalytic phosphine-mediated radical process under mild conditions. This reaction generates a metal-free PR3–H2O radical cation intermediate, in which both hydrogen atoms are used in the subsequent chemical transformation through sequential heterolytic (H+) and homolytic (H) cleavage of the two O–H bonds. The PR3–OH radical intermediate provides an ideal platform that mimics the reactivity of a ‘free’ hydrogen atom, and which can be directly transferred to closed-shell π systems, such as activated alkenes, unactivated alkenes, naphthalenes and quinoline derivatives. The resulting H adduct C radicals are eventually reduced by a thiol co-catalyst, leading to overall transfer hydrogenation of the π system, with the two H atoms of water ending up in the product. The thermodynamic driving force is the strong P=O bond formed in the phosphine oxide by-product. Experimental mechanistic studies and density functional theory calculations support the hydrogen atom transfer of the PR3–OH intermediate as a key step in the radical hydrogenation process.

DOI: 10.1038/s41586-023-06141-1

Source: https://www.nature.com/articles/s41586-023-06141-1