Forming B-B Bonds by the Controlled Reduction of a Tetraaryldiborane(6)
Forming B-B Bonds by the Controlled Reduction of a Tetraaryldiborane(6)
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DOI：
10.1021/jacs.6b02303
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发表时间：
2016-05-18
影响因子：
15
通讯作者：
Wagner, Matthias
中科院分区：
文献类型：
--
作者：
Kaese, Thomas;Huebner, Alexander;Wagner, Matthias
二聚芳基（氢）硼烷可以为通过还原性B-B偶联合成含硼石墨烯薄片提供合适的平台。1，2：1，2-双（4，4 '-二叔丁基-2，2'-亚联苯基）二硼烷（6）（4）与LiNaph/THF的双电子还原建立了B-B σ键，但可能伴随着取代基重新分布。在单一重排产物Li-2[6]中，仅发生一次1，2-苯基位移。双环收缩产物Li-2[7]由两个通过其硼原子连接的9 H-9-硼杂芴基部分组成。当LiNaph/THF的量增加到4当量时，随后观察到Li 2 [6]作为主要物质。加入11当量的LiNaph/THF导致氢化物消除的过度还原，得到双硼掺杂的二苯并[g，p]喹啉Li-2[1]。相比之下，过量的KC 8将4还原为相应的二氢二苯并[g，p]喹啉，K-2[5]，具有trans-HB-BH核心。用1当量的4从K-2[5]中夺取氢得到K[8]，其中中心B-B键由单个氢原子桥接。K[8]也在用1当量的KC 8处理4后获得。所有产物均通过多核NMR光谱和X射线晶体学进行了表征。
Dimeric aryl(hydro)boranes can provide suitable platforms for the synthesis of boron-containing graphene flakes through reductive B-B coupling. Two-electron reduction of 1,2:1,2-bis(4,4'-di-tert-butyl-2,2'-biphenylylene)diborane(6) (4) with LiNaph/THF establishes a B-B sigma bond but can be accompanied by substituent redistribution. In the singly rearranged product, Li-2[6], only one 1,2-phenyl shift has occurred. The doubly ring-contracted product, Li-2[7], consists of two 9H-9-borafluorenyl moieties that are linked via their boron atoms. When the amount of LiNaph/THF is increased to 4 equiv, Li2[6] is subsequently observed as the dominant species. Addition of 11 equiv of LiNaph/THF results in over-reduction with hydride elimination to afford the doubly boron-doped dibenzo[g,p]chrysene Li-2[1]. In contrast, excess KC8 reduces 4 to the corresponding dihydrodibenzo[g,p]chrysene, K-2[5], with a trans-HB-BH core. Hydride abstraction from K-2[5] with 1 equiv of 4 leads to K[8], in which the central B-B bond is bridged by a single hydrogen atom. K[8] is also obtained upon treatment of 4 with 1 equiv of KC8. All products have been characterized by multinuclear NMR spectroscopy and X-ray crystallography.