Density functional theory (DFT) calculations have been performed to provide mechanistic insight into the Rh/Cu co-catalyzed multicomponent annulation of indoles, diazo compounds, and α,β-unsaturated esters. Indole can undergo electrophilic attack by a dirhodium–carbene complex to form a cyclopropane intermediate, which is transferred to an enolate by deprotonation. A dimetallic Michael-type addition reaction is proposed by DFT calculation, where the diastereoselectivity is controlled by the interaction energy between the incoming α,β-unsaturated ester and enolate nucleophile. In copper catalysis, an intramolecular oxidation by copper enolate/copper ketonate resonance is revealed, by which copper enolate is partially oxidized to an α-carbonyl radical. Therefore, intramolecular radical addition with the indole moiety achieves annulation with the formation of a C3 radical in dearomatic indole. Oxidative hydrogen atom transfer then gives the aromatic annulation product by using excess copper chloride.

中文翻译：

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铑-铜级联催化吲哚双C-H圆环的机理研究

已经进行了密度泛函理论（DFT）计算，以提供对Rh / Cu共催化的吲哚，重氮化合物和α，β-不饱和酯的多组分环合的机理的见解。吲哚可以通过二价carb-卡宾络合物进行亲电攻击，形成环丙烷中间体，然后通过去质子化将其转移至烯醇化物中。通过DFT计算提出了双金属迈克尔型加成反应，其中非对映选择性受传入的α，β-不饱和酯与烯醇式亲核试剂之间的相互作用能控制。在铜催化中，揭示了由烯醇铜/铜酮酸酯共振引起的分子内氧化，由此烯醇铜被部分氧化成α-羰基自由基。因此，带有吲哚部分的分子内自由基加成可实现环化反应，并在脱芳族吲哚中形成C3自由基。然后，通过使用过量的氯化铜，氧化性氢原子转移得到芳族环化产物。