Liu Xufang, Dong Shicheng, Zhu Jun, Inoue Shigeyoshi
TUM School of Natural Sciences, Department of Chemistry, Institute of Silicon Chemistry and Catalysis Research Center, Technische Universität München, Lichtenbergstraße 4, Garching bei München 85748, Germany.
State Key Laboratory of Physical Chemistry of Solid Surfaces, Collaborative Innovation Center of Chemistry for Energy Materials (iChem), Fujian Provincial Key Laboratory of Theoretical and Computational Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, China.
J Am Chem Soc. 2024 Aug 21;146(33):23591-23597. doi: 10.1021/jacs.4c08171. Epub 2024 Aug 6.
The activation of C-F bonds has long been regarded as the subject of research in organometallic chemistry, given their synthetic relevance and the fact that fluorine is the most abundant halogen in the Earth's crust. However, C-F bond activation remains a largely unsolved challenge due to the high bond dissociation energies, which was historically dominated by transition metal complexes. Main group elements that can cleave unactivated monofluorobenzene are still quite rare and restricted to s-block complexes with a biphilic nature. Herein, we demonstrate an Al-mediated activation of monofluorobenzene using a neutral dialumene, allowing for the synthesis of the formal oxidative addition products at either double or single aluminum centers. This neutral dialumene system introduces a novel methodology for C-F bond activation based on formal oxidative addition and reductive elimination processes around the two aluminum centers, as demonstrated by combined experimental and computational studies. A "masked" alumylene was unprecedentedly synthesized to prove the proposed reductive elimination pathway. Furthermore, the synthetic utility is highlighted by the functionalization of the resulting aryl-aluminum compounds.
鉴于碳氟键在合成方面的相关性以及氟是地壳中含量最丰富的卤素这一事实，碳氟键的活化长期以来一直被视为有机金属化学的研究课题。然而，由于碳氟键的高键解离能，碳氟键的活化仍然是一个很大程度上未解决的挑战，这一领域在历史上一直由过渡金属配合物主导。能够裂解未活化单氟苯的主族元素仍然相当罕见，并且仅限于具有双亲性质的s区配合物。在此，我们展示了使用中性二铝烯实现铝介导的单氟苯活化，从而能够在双铝中心或单铝中心合成形式上的氧化加成产物。结合实验和计算研究表明，这种中性二铝烯体系基于两个铝中心周围的形式氧化加成和还原消除过程，引入了一种碳氟键活化的新方法。一种“掩蔽”的亚铝烯被前所未有地合成出来，以证明所提出的还原消除途径。此外，所得芳基铝化合物的官能团化突出了其合成实用性。
