We report an iron‐catalyzed decarboxylative C(sp3)–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

中文翻译：

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脂肪族羧酸的一般铁催化脱羧氧化反应

我们报道了在可见光照射下温和、无碱条件下铁催化的脱羧 C(sp3)-O 键形成反应。该转化使用易于获得且结构多样的羧酸、铁光催化剂和2,2,6,6-四甲基哌啶1-氧基（TEMPO）衍生物作为氧化试剂。该过程在具有广泛的立体电子特性和官能团的酸中表现出广泛的范围。所开发的反应应用于一系列生物活性分子的后期氧化。该反应利用铁络合物的能力，通过光诱导的羧酸盐到铁的电荷转移，直接从羧酸产生碳中心自由基。动力学、电化学、EPR、UV-Vis、HRMS 和 DFT 研究表明，TEMPO 在反应中具有三重作用：作为氧化试剂、翻转 Fe 催化剂的氧化剂以及羧酸去质子化的内部碱。获得的 TEMPO 加合物代表了多功能合成中间体，可使用商业有机光催化剂和亲核试剂进一步参与 C-C 和 C-杂原子成键反应