Zhou Wen-Jun, Wang Zhe-Hao, Liao Li-Li, Jiang Yuan-Xu, Cao Ke-Gong, Ju Tao, Li Yiwen, Cao Guang-Mei, Yu Da-Gang
Key Laboratory of Green Chemistry & Technology of Ministry of Education, College of Chemistry, Sichuan University, Chengdu, 610064, China.
College of Chemistry and Chemical Engineering, Neijiang Normal University, Neijiang, 641100, China.
Nat Commun. 2020 Jun 29;11(1):3263. doi: 10.1038/s41467-020-17085-9.
Catalytic reductive coupling of two electrophiles and one unsaturated bond represents an economic and efficient way to construct complex skeletons, which is dominated by transition-metal catalysis via two electron transfer. Herein, we report a strategy of visible-light photoredox-catalyzed successive single electron transfer, realizing dearomative arylcarboxylation of indoles with CO. This strategy avoids common side reactions in transition-metal catalysis, including ipso-carboxylation of aryl halides and β-hydride elimination. This visible-light photoredox catalysis shows high chemoselectivity, low loading of photocatalyst, mild reaction conditions (room temperature, 1 atm) and good functional group tolerance, providing great potential for the synthesis of valuable but difficultly accessible indoline-3-carboxylic acids. Mechanistic studies indicate that the benzylic radicals and anions might be generated as the key intermediates, thus providing a direction for reductive couplings with other electrophiles, including DO and aldehyde.
两个亲电试剂与一个不饱和键的催化还原偶联是构建复杂骨架的一种经济有效的方法，该方法主要通过过渡金属催化的双电子转移来实现。在此，我们报道了一种可见光光氧化还原催化的连续单电子转移策略，实现了吲哚与CO的去芳构化芳基羧基化反应。该策略避免了过渡金属催化中常见的副反应，包括芳基卤化物的本位羧基化和β-氢消除反应。这种可见光光氧化还原催化表现出高化学选择性、低光催化剂负载量、温和的反应条件（室温，1个大气压）以及良好的官能团耐受性，为合成有价值但难以获得的吲哚啉-3-羧酸提供了巨大潜力。机理研究表明，苄基自由基和阴离子可能作为关键中间体生成，从而为与其他亲电试剂（包括DO和醛）的还原偶联提供了方向。
