Planar chiral ferrocenes are widely applied in organic synthesis, materials science, and medicinal chemistry, but their synthesis is not trivial. Herein, a highly efficient synthesis of planar chiral ferrocene-based pyridine derivatives via Rh(I)-catalyzed direct coupling of pyridylferrocenes with aryl halides was developed. Good yields and excellent enantioselectivity (95– >99% ee) are obtained for a wide range of substrates. The compatibility of gram-scale synthesis and relatively low catalyst loading (down to 1 mol% based on [Rh]) enhance the practicality of the current method. The generated coupling products can be readily transformed into chiral ligands. Mechanistic studies suggest that the C–H bond cleavage of pyridylferrocene may be a reversible step and not the rate-determining step. Significant nonlinear effects indicate the existence of multiple metals or ligands in the active catalyst.

中文翻译：

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铑催化的吡啶辅助的CH芳基化反应合成平面手性二茂铁

平面手性二茂铁广泛用于有机合成，材料科学和药物化学中，但合成并不简单。本文中，开发了通过Rh（I）催化的吡啶基二茂铁与芳基卤化物的直接偶联，高效合成平面手性二茂铁基吡啶衍生物。对于多种底物，均具有良好的产率和出色的对映选择性（95-> 99％ee）。克级合成和较低的催化剂负载量（基于[Rh]低至1 mol％）的相容性增强了当前方法的实用性。产生的偶联产物可以容易地转化为手性配体。机理研究表明，吡啶基二茂铁的C–H键裂解可能是可逆的步骤，而不是速率决定步骤。