Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University, 637371, Singapore.
J Am Chem Soc. 2021 Nov 3;143(43):18172-18180. doi: 10.1021/jacs.1c07389. Epub 2021 Oct 26.
Since aluminum is the most electropositive element among the p-block elements, the construction of molecules bearing a dianionic Al-Al σ-bond is inherently highly challenging. Herein, we report the first synthesis of a dianionic dialane(6) based on the AlO three-membered ring scaffold, namely, an aluminum analog of oxirane. The structure of has been unambiguously ascertained by spectroscopic analysis as well as X-ray crystallography, and computational studies revealed that bears a highly strained Al-Al σ-bond. readily reacts with the unsaturated substrates such as isocyanide, ethylene, and ketone, concomitant with the cleavage of the Al-Al σ-bond under mild conditions, leading to the four- and five-membered heterocycles -. Furthermore, the reaction of with two molecules of benzonitrile (PhCN) furnishes a seven-membered heterocycle , resulting from the C-C coupling reaction of PhCN. We further delineate that selectively activates an arene ring C-C bond of biphenylene, rendering a di-Al-substituted benzo[8]annulene derivative . Preliminary computational studies propose that the stepwise reaction mechanism involves the Al-Al σ-bond cleavage, dearomative Al-C bond formation, subsequent sigmatropic [1,3]shifts, and a pericyclic reaction.
由于铝是 p 区元素中最具正电性的元素，因此构建带有二价阴离子 Al-Al σ 键的分子在本质上极具挑战性。在此，我们报告了首例基于 AlO 三原子环支架的二价二烷（6）的合成，即环氧乙烷的铝类似物。通过光谱分析以及 X 射线晶体学明确确定了 的结构，计算研究表明 具有高度应变的 Al-Al σ 键。 可与不饱和底物（如异氰化物、乙烯和酮）反应，同时在温和条件下断裂 Al-Al σ 键，生成四元和五元杂环-。此外， 与两分子苯甲腈（PhCN）反应生成七元杂环-，这是 PhCN 的 C-C 偶联反应的结果。我们进一步阐明， 选择性地激活联苯的芳环 C-C 键，生成二铝取代的苯并[8]轮烯衍生物-。初步的计算研究表明，分步反应机制涉及 Al-Al σ 键的断裂、去芳构化的 Al-C 键形成、随后的[1,3]迁移和周环反应。
