Denkler Luca Mareen, Aladahalli Shekar Meghana, Ngan Tak Shing Jason, Wylie Luke, Abdullin Dinar, Engeser Marianne, Schnakenburg Gregor, Hett Tobias, Pilz Frank Hendrik, Kirchner Barbara, Schiemann Olav, Kielb Patrycja, Bunescu Ala
Kekulé Institute for Organic Chemistry and Biochemistry, Universität Bonn, Gerhard-Domagk-Straße1, 53121, Bonn, Germany.
Mulliken Center for Theoretical Chemistry Clausius Institute for Physical and Theoretical Chemistry, Universität Bonn, Beringstraße 4, 53115, Bonn, Germany.
Angew Chem Int Ed Engl. 2024 Aug 5;63(32):e202403292. doi: 10.1002/anie.202403292. Epub 2024 Jul 3.
We report an iron-catalyzed decarboxylative C(sp)-O bond-forming reaction under mild, base-free conditions with visible light irradiation. The transformation uses readily available and structurally diverse carboxylic acids, iron photocatalyst, and 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) derivatives as oxygenation reagents. The process exhibits a broad scope in acids possessing a wide range of stereoelectronic properties and functional groups. The developed reaction was applied to late-stage oxygenation of a series of bio-active molecules. The reaction leverages the ability of iron complexes to generate carbon-centered radicals directly from carboxylic acids by photoinduced carboxylate-to-iron charge transfer. Kinetic, electrochemical, EPR, UV/Vis, HRMS, and DFT studies revealed that TEMPO has a triple role in the reaction: as an oxygenation reagent, an oxidant to turn over the Fe-catalyst, and an internal base for the carboxylic acid deprotonation. The obtained TEMPO adducts represent versatile synthetic intermediates that were further engaged in C-C and C-heteroatom bond-forming reactions using commercial organo-photocatalysts and nucleophilic reagents.
我们报道了一种在温和、无碱条件下，可见光照射下铁催化的脱羧C(sp)-O键形成反应。该转化反应使用易于获得且结构多样的羧酸、铁光催化剂以及2,2,6,6-四甲基哌啶1-氧基（TEMPO）衍生物作为氧化试剂。该过程在具有广泛立体电子性质和官能团的酸中具有广泛的适用范围。所开发的反应应用于一系列生物活性分子的后期氧化反应。该反应利用了铁配合物通过光诱导的羧酸根到铁的电荷转移直接从羧酸生成碳中心自由基的能力。动力学、电化学、电子顺磁共振、紫外可见光谱、高分辨质谱和密度泛函理论研究表明，TEMPO在反应中具有三重作用：作为氧化试剂、使铁催化剂循环的氧化剂以及羧酸去质子化的内碱。所得到的TEMPO加合物代表了通用的合成中间体，它们使用市售有机光催化剂和亲核试剂进一步参与C-C键和C-杂原子键形成反应。
