The palladium-catalysed cross-coupling reaction between alkenes and aryl halides (the Mizoroki–Heck reaction) is a powerful methodology to construct new carbon–carbon bonds. However, the success of this reaction is in part hampered by an extremely marked regioselectivity on the double bond, which dictates that electron-poor alkenes react exclusively on the β-carbon. Here, we show that ligand-free, few-atom palladium clusters in solution catalyse the α-selective intramolecular Mizoroki–Heck coupling of iodoaryl cinnamates, and mechanistic studies support the formation of a sterically encumbered cinnamate–palladium cluster intermediate. Following this rationale, the α-selective intermolecular coupling of aryl iodides with styrenes is also achieved with palladium clusters encapsulated within fine-tuned and sterically restricted zeolite cavities to produce 1,1-bisarylethylenes, which are further engaged with aryl halides by a metal-free photoredox-catalysed coupling. These ligand-free methodologies significantly expand the chemical space of the Mizoroki–Heck coupling.

烯烃和芳基卤化物之间的钯催化交叉偶联反应（Mizoroki-Heck 反应）是构建新碳-碳键的有效方法。然而，该反应的成功部分受到双键上极其显着的区域选择性的阻碍，这表明缺电子烯烃仅在 β-碳上反应。在这里，我们表明溶液中的无配体、少原子钯簇催化碘芳基肉桂酸酯的α-选择性分子内 Mizoroki-Heck 偶联，并且机理研究支持形成空间位阻肉桂酸酯-钯簇中间体。按照这个道理，芳基碘化物与苯乙烯的α-选择性分子间偶联也可以通过封装在微调和空间受限沸石腔内的钯簇来实现，以产生 1,1-双芳基乙烯，其通过无金属光氧化还原催化进一步与芳基卤化物结合耦合。这些无配体方法显着扩展了 Mizoroki-Heck 偶联的化学空间。