Transition-metal catalyzed couplings of aryl halides or arenes with aryl organometallics, as well as direct reductive coupling of two aryl halides, are the predominant methods to synthesize biaryls. However, stoichiometric amounts of metals are inevitably utilized in these reactions, either in the pre-generation of organometallic reagents or acting as reductant in situ, thus producing quantitative metal waste. Herein, we demonstrate that this longstanding challenge can be overcome with N₂H₄ as a metal surrogate. The fundamental innovation of this strategy is that N₂ and H₂ are generated as side products, which readily escape from the system after the reaction. The success of both homo- and cross-coupling of various aryl electrophiles bearing a wide range of functional groups manifests the powerfulness and versatility of this strategy. Furthermore, both homo- and cross-couplings of a series of alkaloids, amino acids and steroids exemplify application of this protocol in the functionalization of biologically active molecules.

中文翻译：

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N 2 H 4作为均芳基和交叉芳基偶联的无痕迹介体。

芳基卤化物或芳烃与芳基有机金属的过渡金属催化偶联以及两个芳基卤化物的直接还原偶联是合成联芳基的主要方法。但是，在这些反应中，无论是在有机金属试剂的预生成中还是在原位充当还原剂，都不可避免地要使用化学计量的金属。在本文中，我们证明了使用N ₂ H ₄作为金属替代物可以克服这一长期挑战。该策略的根本创新在于N ₂和H ₂产生的副产物在反应后容易从系统中逸出。带有广泛官能团的各种芳基亲电子试剂的均相和交叉偶联均获得成功，证明了该策略的强大功能和多功能性。此外，一系列生物碱，氨基酸和类固醇的同型和交叉偶联都例证了该方案在生物活性分子功能化中的应用。