A tricyclic annulated 1,4,2-diazaborole is readily accessed via reaction of a bidentate pyridyl-carbene ligand with MesBBr₂ followed by reduction. Dearomatization of the flanking rings is shown to increase reactivity of this heterocycle in the form of a B-centred alkylation with MeI. Its reaction with hydrido-, fluoro-, and chloro-boranes reveal an unprecedented ring expansion reaction to form a diverse family of B₂C₂N₂ heterocycles, reduction of which allows facile access to the first examples of C_s symmetric 1,4,2,5-diazadiborinines. DFT calculations have shed light on the electronic structures of the reduced species and provide insight into mechanistic aspects of the observed ring-expansion.

中文翻译：

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环状 1,4,2-二氮杂硼杂环戊烯中的芳香性转移：轻松获得 Cs 对称 1,4,2,5-二氮杂二硼啉


通过双齿吡啶基卡宾配体与 MesBBr ₂ 反应，然后还原，可以轻松获得三环环状 1,4,2-二氮硼杂环。侧翼环的脱芳构化以与 MeI 进行的以 B 为中心的烷基化形式增加了该杂环的反应性。它与氢硼烷、氟硼烷和氯硼烷的反应揭示了前所未有的扩环反应，形成了多种 B ₂ C ₂ N ₂ 杂环家族，对其进行还原可以轻松获得 C _s 对称 1,4,2,5-二氮杂二硼啉的第一个例子。 DFT 计算揭示了还原物质的电子结构，并提供了对所观察到的环膨胀的机制方面的深入了解。