Sindlinger Marvin, Ströbele Markus, Grunenberg Jörg, Bettinger Holger F
Institut für Organische Chemie, Universität Tübingen Auf der Morgenstelle 18 72076 Tübingen Germany.
Institut für Anorganische Chemie, Universität Tübingen Auf der Morgenstelle 18 72076 Tübingen Germany.
Chem Sci. 2023 Sep 13;14(38):10478-10487. doi: 10.1039/d3sc03433j. eCollection 2023 Oct 4.
Benzoborirenes are a very rare class of strained boron heterobicyclic systems. In this study a kinetically stabilized benzoborirene 1 is shown to react with multiple bonds of trimethylphosphine oxide, acetaldehyde, and -butyl isonitrile. The (2 + 2) cycloaddition product with trimethylphosphine oxide, benzo[][1,2,5]oxaphosphaborole, has a long apical PO bond (194.0 pm) that must be considered on the border line between ionic and covalent according to the natural bond orbital, quantum theory of atoms in molecules, and compliance matrix approaches to the description of chemical bonding. The coordination compound between the benzoborirene and phosphine oxide was observed by NMR spectroscopy at 213 K. The Lewis acidity of 1 is similar to that of B(OCHCF) and B(CF) based on the P{H} NMR chemical shift of the Lewis acid base complexes with trimethylphosphine oxide at 213 K. Benzoboriene 1 does not react with acetone, but forms a (2 + 2) cycloaddition product, an oxaborole, with acetaldehyde. In contrast, it undergoes a double (2 + 1) reaction with -butyl isonitrile to yield a boro-indane derivative under mild conditions. The observed reactivity of 1 is in agreement with computational analyses of the respective potential energy surfaces.
苯并硼杂环丁二烯是一类非常罕见的张力硼杂双环体系。在本研究中，一种动力学稳定的苯并硼杂环丁二烯1被证明能与三甲基氧化膦、乙醛和异丁腈的多重键发生反应。与三甲基氧化膦形成的(2 + 2)环加成产物苯并[][1,2,5]氧杂磷硼杂环丁烷，具有较长的顶端P—O键（194.0 pm），根据自然键轨道、分子中原子的量子理论以及用于描述化学键合的顺从矩阵方法，该键必须被视为处于离子键和共价键的边界线上。在213 K下通过核磁共振光谱观察到了苯并硼杂环丁二烯与氧化膦之间的配位化合物。基于213 K下与三甲基氧化膦形成的路易斯酸碱配合物的P{H}核磁共振化学位移，1的路易斯酸性与B(OCHCF)和B(CF)相似。苯并硼杂环丁二烯1不与丙酮反应，但与乙醛形成(2 + 2)环加成产物氧杂硼杂环丁烷。相反，在温和条件下，它与异丁腈发生双(2 + 1)反应，生成硼代茚衍生物。观察到的1的反应活性与相应势能面的计算分析结果一致。
