Transition metal–catalyzed cross-coupling reactions are some of the most widely used methods in chemical synthesis. However, despite notable advantages of iron (Fe) as a potentially cheaper, more abundant, and less toxic transition metal catalyst, its practical application in multicomponent cross-couplings remains largely unsuccessful. We demonstrate 1,2-bis(dicyclohexylphosphino)ethane Fe–catalyzed coupling of α-boryl radicals (generated from selective radical addition to vinyl boronates) with Grignard reagents. Then, we extended the scope of these radical cascades by developing a general and broadly applicable Fe-catalyzed multicomponent annulation–cross-coupling protocol that engages a wide range of π-systems and permits the practical synthesis of cyclic fluorous compounds. Mechanistic studies are consistent with a bisarylated Fe(II) species being responsible for alkyl radical generation to initiate catalysis, while carbon-carbon bond formation proceeds between a monoarylated Fe(II) center and a transient alkyl radical.

中文翻译：

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铁催化多组分自由基级联-交叉偶联的一般方法

过渡金属催化的交叉偶联反应是化学合成中应用最广泛的一些方法。然而，尽管铁 (Fe) 作为一种潜在的更便宜、更丰富、毒性更小的过渡金属催化剂具有显着优势，但其在多组分交叉偶联中的实际应用仍然很大程度上不成功。我们展示了 1,2-双（二环己基膦基）乙烷 Fe 催化的 α-硼基自由基（由选择性自由基加成到乙烯基硼酸盐产生）与格氏试剂的偶联。然后，我们通过开发一种通用且广泛适用的 Fe 催化多组分环化-交叉偶联方案扩展了这些自由基级联的范围，该方案涉及广泛的 π 系统并允许实际合成环状氟化合物。