In this paper, we report a palladium-catalyzed dual C–H activation of N-phenyl-1H-indole-3-carboxamides for the synthesis of 5,11-dihydro-6H-indolo[3,2-c]quinolin-6-ones. The optimal reaction conditions were to use 20 mol % of Pd(TFA)₂ as the catalyst, 2.0 equivalents of Cu(OAc)₂ as the oxidant, 1.0 equivalent of K₃PO₄ as the base, and 3.0 equivalents of PivOH as the additive in DMF/dioxane (1: 9). When carried out at 120 °C for 24 h, the reaction could provide nineteen target indoloquinolinones in modest to excellent yields, including the N,N′-dimethylated and N,N′-unsubstituted products which are inaccessible by the reported C–H activation methodologies. The dual C–H activation reaction was also applicable to N-phenyl-1H-indole-2-carboxamides and formed the corresponding 5,7-dihydro-6H-indolo[2,3-c]quinolin-6-ones. A plausible reaction mechanism based on the data from the control experiments and the literatures was proposed to account for the transformation.

中文翻译：

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钯催化 N-苯基-1H-吲哚-3-甲酰胺双 C-H 活化合成 5,11-二氢-6H-吲哚[3,2-c]喹啉-6-酮

在本文中，我们报道了钯催化的N-苯基-1H-吲哚-3-甲酰胺的双C-H活化，用于合成5,11-二氢-6H-吲哚并[3,2- c ]喹啉-6个。最佳反应条件为：20 mol%的Pd(TFA) ₂为催化剂，2.0当量的Cu(OAc) ₂为氧化剂，1.0当量的K ₃ PO ₄为碱，3.0当量的PivOH为反应剂。添加剂 DMF/二恶烷 (1:9)。当在 120 °C 下进行 24 小时时，该反应可以以中等至优异的收率提供 19 种目标吲哚喹啉酮，包括N , N '-二甲基化和N , N '-未取代的产物，这些产物是通过报道的 C-H 活化无法获得的方法论。双C-H活化反应也适用于N-苯基-1H-吲哚-2-甲酰胺并形成相应的5,7-二氢-6H-吲哚[2,3- c ]喹啉-6-酮。基于对照实验和文献的数据，提出了一种合理的反应机制来解释这种转变。