AbstractA divergent synthetic approach to access highly substituted indole scaffolds is illustrated. By virtue of a tunable electrochemical strategy, distinct control over the C‐3 substitution pattern was achieved by employing two analogous 2‐styrylaniline precursors. The chemoselectivity is governed by the fine‐tuning of the acidity of the amide proton, relying on the appropriate selection of N‐protecting groups, and assisted by the reactivity of the electrogenerated intermediates. Detailed mechanistic investigations based on cyclic voltametric experiments and computational studies revealed the crucial role of water additive, which assists the proton‐coupled electron transfer event for highly acidic amide precursors, followed by an energetically favorable intramolecular C−N coupling, causing exclusive fabrication of the C‐3 unsubstituted indoles. Alternatively, the implementation of an electrogenerated cationic olefin activator delivers the C‐3 substituted indoles through the preferential nucleophilic nature of the N‐acyl amides. This electrochemical approach of judicious selection of N‐protecting groups to regulate pKa/E° provides an expansion in the domain of switchable generation of heterocyclic derivatives in a sustainable fashion, with high regio‐ and chemoselectivity.
摘要 阐述了一种获得高取代吲哚支架的不同合成方法。通过可调电化学策略,采用两种类似的 2-苯乙烯基苯胺前体实现了对 C-3 取代模式的独特控制。化学选择性受制于酰胺质子酸度的微调、N 保护基团的适当选择以及电生成中间体的反应性。基于循环伏安实验和计算研究的详细机理研究表明,水添加剂起着至关重要的作用,它有助于高酸性酰胺前体的质子耦合电子转移事件,随后是能量上有利的分子内 C-N 偶联,导致 C-3 未取代吲哚的独家制造。或者,使用电生阳离子烯烃活化剂,通过 N-酰基酰胺的优先亲核性,生成 C-3 取代的吲哚。这种明智选择 N 保护基团以调节 pKa/E° 的电化学方法,以可持续的方式扩展了可切换生成杂环衍生物的领域,并具有很高的区域和化学选择性。