Liu Chen-Xu, Xie Pei-Pei, Zhao Fangnuo, Wang Quannan, Feng Zuolijun, Wang Haoyang, Zheng Chao, You Shu-Li
State Key Laboratory of Organometallic Chemistry, Shanghai Institute of Organic Chemistry, University of Chinese Academy of Sciences, Chinese Academy of Sciences, 345 Lingling Lu, Shanghai 200032, China.
J Am Chem Soc. 2023 Mar 1;145(8):4765-4773. doi: 10.1021/jacs.2c13542. Epub 2023 Feb 14.
Mechanism-guided reaction development is a well-appreciated research paradigm in chemistry since the merging of mechanistic knowledge would accelerate the discovery of new synthetic methods. Low-valent transition metals such as Pd(0)- and Rh(I)-catalyzed C-H arylation with aryl (pseudo)halides is among the enabling reactions for the exclusive cross-coupling of two different aryl partners. However, different from the situation of Pd(0)-catalysis, the mechanism of Rh(I)-catalyzed C-H arylation is underexplored. The sequence of the elementary steps of aryl C-H activation and oxidative addition of aryl (pseudo)halides remains unclear. Herein, we report comprehensive experimental and computational studies toward explicit mechanistic understandings of Rh(I)-catalyzed intermolecular asymmetric C-H arylation between 2-pyridinylferrocenes and aryl bromides. The identification of each elementary step in the catalytic cycle and the structural characterization of the key intermediates and transition states allow the rational design and development of challenging intramolecular reactions. The successful realization of this reaction mode set the foundation for the facile synthesis of planar chiral []ferrocenophanes ( = 6-8), a class of rarely explored target molecules with strained structures and intriguing molecular topology.
自机械化学知识融合以来，机理导向的反应开发一直是化学领域备受关注的研究范式，因为机理知识的融合会加速新合成方法的发现。低价过渡金属催化的芳基（伪）卤化物与芳基之间的C-H芳基化反应，如Pd(0)和Rh(I)催化的反应，是实现两种不同芳基伙伴专一性交叉偶联的关键反应之一。然而，与Pd(0)催化的情况不同，Rh(I)催化的C-H芳基化反应机理尚未得到充分探索。芳基C-H活化和芳基（伪）卤化物氧化加成的基本步骤顺序仍不清楚。在此，我们报告了全面的实验和计算研究，旨在明确了解Rh(I)催化的2-吡啶基二茂铁与芳基溴之间的分子间不对称C-H芳基化反应机理。催化循环中每个基本步骤的确定以及关键中间体和过渡态的结构表征，为具有挑战性的分子内反应的合理设计和开发提供了依据。这种反应模式的成功实现为平面手性[]二茂铁环（ = 6-8）的简便合成奠定了基础，这是一类很少被探索的具有应变结构和有趣分子拓扑结构的目标分子。
