Synthesis and Structural Characterization of 9-Azido-9-Borafluorene: Monomer and Cyclotrimer of a Borole Azide
Synthesis and Structural Characterization of 9-Azido-9-Borafluorene: Monomer and Cyclotrimer of a Borole Azide
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DOI：
10.1021/ic902436s
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发表时间：
2010-05-17
影响因子：
4.6
通讯作者：
Bettinger, Holger F.
中科院分区：
文献类型：
--
作者：
Biswas, Sunanda;Oppel, Iris M.;Bettinger, Holger F.
以正己烷为溶剂，由2，2‘-二溴联苯和n-BuLi生成的2，2’-二锂硫代联苯与BCl3反应，提供了一条高产率、简单的9-氯-9-硼氟烯La的制备路线。化合物2在固体状态下以环状三聚体形式存在，但在二氯甲烷溶液中可与三聚体共存。叠氮化合物2在固体和溶液中都很不稳定，它与微量的水和氧气一起转化为1，3，5-三(2-联苯基)环三硼氧烷，X-射线衍射法对其进行了表征。在叠氮化合物2上加成吡啶和叔丁基吡啶，得到相应的吡啶加合物。化合物La和2的Lewis碱加合物均经多核核磁共振波谱确证，结构经X-射线衍射法确证。用计算化学方法在MP2理论水平上研究了叠氮化合物2的结构特征及其硼中心的强Lewis酸性。
The reaction of 2,2'-dilithiobiphenyl, generated from 2,2'-dibromobiphenyl and n-BuLi, with BCl3 using n-hexane as solvent provides a high-yielding, simple preparative route to 9-chloro-9-borafluorene la. This in turn can be reacted with trimethylsilyl azide to yield 9-azido-9-borafluorene 2. Compound 2 exists as a cyclic trimer in the solid state, but in dichloromethane solution the monomer can coexist with the trimer. Azide 2 is rather unstable both in the solid state and in solution, and it transforms with trace amounts of water and oxygen to the 1,3,5-tris(2-biphenylyl)cyclotriboroxane that was characterized by X-ray diffraction analysis. Addition of pyridine and t-butyl pyridine to azide 2 afford the corresponding pyridine adducts. Compound la as well as the Lewis base adducts of 2 have been characterized by multinuclear NMR spectroscopy, and the structures were confirmed by X-ray diffraction analysis. The structural features of azide 2 and the strong Lewis acidity of its boron center have also been investigated by computational chemistry techniques at the MP2 level of theory.