Nucleophilic (Radio)Fluorination of Redox-Active Esters via Radical-Polar Crossover Enabled by Photoredox Catalysis
Nucleophilic (Radio)Fluorination of Redox-Active Esters via Radical-Polar Crossover Enabled by Photoredox Catalysis
复制标题
通过光氧化还原催化实现的自由基-极性交叉对氧化还原活性酯进行亲核（放射性）氟化
DOI：
10.1021/jacs.0c03125
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发表时间：
2020
影响因子：
15
通讯作者：
Doyle, Abigail G.
中科院分区：
文献类型：
--
作者：
Webb, Eric W.;Park, John B.;Cole, Erin L.;Donnelly, David J.;Bonacorsi, Samuel J.;Ewing, William R.;Doyle, Abigail G.
我们报道了一种在可见光照射下用红外光催化剂对N-羟基邻苯二甲酰亚胺酯进行亲核氟化的氧化还原中性方法。该方法提供了广泛的脂族氟化物的途径，包括伯基、仲基和叔基氟化物以及未活化的叔基氟化物，由于竞争消除，通常不能通过亲核氟化反应获得这些化合物。此外，我们还表明，脱羧基氟化条件很容易适应于用[18F]KF进行放射性氟化。我们认为，反应通过Ir催化剂和氧化还原活性酯底物之间的两个电子转移进行，以提供碳正离子中间体，该中间体随后经历氟化物的捕获。还给出了用O和C中心的亲核剂捕获和脱氧氟化Van-羟基邻苯二甲酰亚胺草酸酯的例子，表明这种方法可能为在温和的条件下影响氧化还原中性SN1取代提供一个总体蓝图。
We report a redox-neutral method for nucleophilic fluorination ofN-hydroxyphthalimide esters using an Ir photocatalyst under visible light irradiation. The method provides access to a broad range of aliphatic fluorides, including primary, secondary, and tertiary benzylic fluorides as well as unactivated tertiary fluorides, that are typically inaccessible by nucleophilic fluorination due to competing elimination. In addition, we show that the decarboxylative fluorination conditions are readily adapted to radiofluorination with [18F]KF. We propose that the reactions proceed by two electron transfers between the Ir catalyst and redox-active ester substrate to afford a carbocation intermediate that undergoes subsequent trapping by fluoride. Examples of trapping with O- and C-centered nucleophiles and deoxyfluorination viaN-hydroxyphthalimidoyl oxalates are also presented, suggesting that this approach may offer a general blueprint for affecting redox-neutral SN1 substitutions under mild conditions.