Zhu Lizhao, Kinjo Rei
School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, Nanyang Link 21, Singapore, 637371, Singapore.
Angew Chem Int Ed Engl. 2023 Nov 20;62(47):e202312949. doi: 10.1002/anie.202312949. Epub 2023 Oct 25.
N-Substitution of a thermally unstable diboratriazole 1 with a trimethylsilyl group affords a remarkably stable diboratriazole derivative 2. Ring contraction of 2 with an N-heterocyclic carbene accompanied by the release of N as well as 1,4-hydrogen shift affords a carbene-stabilized azadiboriridine 3. Abstraction of the H-B hydride in 3 with methyl trifluoromethanesulfonate leads to the isolation of a hitherto unknown azadiboriridinylium 4, the first BN analogue of cyclopropenylium cation. X-ray diffraction analysis and computational studies confirmed the delocalization of π electrons over the B N three-membered ring, indicating the 2π aromatic feature. Compound 4 undergoes ring expansion reactions with azobenzene and pyridazine to furnish triazadiborolidinylium species 5 and 6, the latter of which possesses a cationic B N ring with a pronounced 6π aromatic property. Moreover, the reaction of 4 with a diazo compound produces a cationic B N C pentafulvene derivative 7.
用三甲基硅基对热不稳定的二硼三唑1进行N-取代，得到一种非常稳定的二硼三唑衍生物2。2与N-杂环卡宾发生环收缩，同时释放出N并伴有1,4-氢迁移，得到卡宾稳定的氮杂二硼环丁烷3。用三氟甲磺酸甲酯脱去3中的H-B氢化物，分离得到一种迄今未知的氮杂二硼环丁烯鎓4，它是环丙烯鎓阳离子的首个硼氮类似物。X射线衍射分析和计算研究证实了π电子在硼氮三元环上的离域，表明其具有2π芳香特征。化合物4与偶氮苯和哒嗪发生扩环反应，生成三氮杂二硼戊环鎓物种5和6，其中后者具有一个具有明显6π芳香性质的阳离子硼氮环。此外，4与重氮化合物反应生成阳离子硼氮碳戊搭烯衍生物7。
