Xu Jiaping, Dai Chuan-Ming, Xu Xin, Jian Jiwen
Hangzhou Institute of Advanced Studies, Zhejiang Normal University, 1108 Gengwen Road, Hangzhou, Zhejiang 311231, China.
Hangzhou Institute of Advanced Studies, Zhejiang Normal University, 1108 Gengwen Road, Hangzhou, Zhejiang 311231, China.
Spectrochim Acta A Mol Biomol Spectrosc. 2024 Jan 15;305:123539. doi: 10.1016/j.saa.2023.123539. Epub 2023 Oct 14.
Six boron heterocyclic radicals with different conformations or configurations were synthesized in solid neon and identified by matrix isolation infrared spectroscopy as well as quantum-chemical calculations. The ground-state boron atom selectively attacks the C = C bond of cycloheptene forming η (1,2)-BCH complex (A), which contains a chair conformation and a boat conformation. Species A isomerizes to the 2,3,4,5,6,7-hexahydroborocine radical (B), which involves an eight-membered boron heterocyclic ring and also has two isomers observed. The 1-(prop-1-en-1-yl)-2,3,4-dihydro borole radical (C) with E-configuration and Z-configuration is generated as the final product under UV light irradiation through ring contraction reaction and the hydrogen atom transfer reaction. The observation of species A and further photo-isomerization to species C is consistent with theoretical predictions that these reactions are thermodynamically exothermic and kinetically facile. This work not only provides a possible route for future design and synthesis of corresponding borole derivatives, but also provides new insights into the structural and spectroscopic information of boron heterocyclic radicals with different conformations and configurations.
六种具有不同构象或构型的硼杂环自由基在固体氖中合成，并通过基质隔离红外光谱以及量子化学计算进行了鉴定。基态硼原子选择性地进攻环庚烯的C = C键，形成η(1,2)-BCH配合物(A)，它包含椅式构象和船式构象。物种A异构化为2,3,4,5,6,7-六氢硼嗪自由基(B)，它涉及一个八元硼杂环，并且也观察到有两种异构体。具有E构型和Z构型的1-(丙-1-烯-1-基)-2,3,4-二氢硼戊环自由基(C)在紫外光照射下通过环收缩反应和氢原子转移反应作为最终产物生成。对物种A的观察以及进一步光异构化为物种C与理论预测一致，即这些反应在热力学上是放热的且在动力学上是容易的。这项工作不仅为未来相应硼戊环衍生物的设计和合成提供了一条可能的途径，而且为具有不同构象和构型的硼杂环自由基的结构和光谱信息提供了新的见解。
