A [6 + 1] annulation reaction via cascade 1,6-hydride transfer/cyclization is reported to construct a polycyclic 3,4-fused azepinoindole skeleton. The newly designed 4-amino-indole-3-carbaldehyde is applied as a novel six-atom synthon, interacting with arylamines and malononitrile to achieve the [6 + 1] annulation. Notably, the reaction proceeds smoothly under redox-neutral and metal-free conditions, providing a wide range of azepinoindoles in up to 94% yields, with water as the only byproduct. Besides, the advantage of high step- and atom-economy further highlights the practicality of this methodology.

中文翻译：

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1,6-氢化物转移启用的 [6 + 1] 环化以获得多环 3,4-稠合氮杂吲哚

据报道，通过级联 1,6-氢化物转移/环化的 [6 + 1] 环化反应构建了多环 3,4-稠合氮杂吲哚骨架。新设计的4-氨基-吲哚-3-甲醛被用作新型六原子合成子，与芳胺和丙二腈相互作用以实现[6 + 1]环化。值得注意的是，该反应在氧化还原中性和无金属条件下顺利进行，提供了多种氮杂吲哚，产率高达 94%，水是唯一的副产物。此外，高步骤经济性和原子经济性的优势进一步凸显了该方法的实用性。