Electrophilic aromatic substitution reactions are of profound importance for the synthesis of biologically active compounds and other advanced materials. They represent an important means to activate specific aromatic C–H bonds without requiring transition-metal catalysts. Surprisingly, few stereoselective variants are known for electrophilic aromatic substitutions, which limits the utility of these classical reactions for stereoselective synthesis. While many electrophilic aromatic substitutions lead to achiral products (due to the planar nature of aromatic rings), there are important examples where chiral products are produced, including desymmetrization reactions of aromatic cyclophanes and of prochiral substrates with multiple aromatic rings. This Synpacts article now illustrates how chiral arms, when placed precisely above and underneath delocalized carbocations, can act as chiral auxiliaries to convert classical electrophilic aromatic substitution reactions into powerful diastereo- and enantioselective transformations.

中文翻译：

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立体选择性亲电芳香取代的手性助剂

亲电芳香取代反应对于合成生物活性化合物和其他先进材料具有极其重要的意义。它们代表了一种无需过渡金属催化剂即可激活特定芳族 C-H 键的重要手段。令人惊讶的是，几乎没有已知的用于亲电芳香取代的立体选择性变体，这限制了这些经典反应在立体选择性合成中的应用。虽然许多亲电芳香取代导致非手性产物（由于芳香环的平面性质），但也有一些重要的例子可以产生手性产物，包括芳香环芳烃和具有多个芳香环的前手性底物的去对称化反应。这篇 Synpacts 文章现在说明了手性臂如何，