syn-1,2-carboboration of alkynes with borenium cations.
syn-1,2-carboboration of alkynes with borenium cations.
复制标题
与硼阳离子的炔烃的Syn-1,2-晶状体。
DOI：
10.1002/chem.201403614
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发表时间：
2014-09-26
影响因子：
4.3
通讯作者：
Ingleson, Michael J.
中科院分区：
文献类型：
--
作者：
Cade, Ian A.;Ingleson, Michael J.
8-（三甲基甲硅烷氧基）喹啉（QOTMS）与BCl 3和（芳基）BCl 2反应形成QOBCl 2和QOBCl（芳基）。随后添加的化学计量的AlCl 3遵循两种路径之一，取决于QO配体的空间需求和所得到的borenium阳离子的亲电性。形成了苯基和5-己基噻吩基硼鎓阳离子QOBPh+和QOBTh+，而QOBCl+则没有。相反，AlCl 3优先与QOBCl 2在氧结合，形成QOBCl 2取代AlCl 3，而不是提取氯化物。通过在喹啉配体的7位安装甲基，适度增加氧周围的空间需求，将与AlCl 3的反应性切换回氯化物提取，从而形成QOBCl+。所有制备的Borenium阳离子都是高度亲氯的，并表现出与AlCl 4 −的显著相互作用，导致刘易斯酸性“AlCl 3”物种的平衡浓度。“AlCl 3”物质的存在限制了与这些borenium系统相容的炔底物，[QOBPh][AlCl 4]与1-戊炔的反应仅产生环三聚产物1，3，5-三丙基苯。相反，QOBPh+和QOBTh+系统影响3-己炔的顺-1，2-硼碳化。在M06-2X/6- 311 G（d，p）/PCM（DCM）水平上的DFT计算证实了Ph相对于Me更高的迁移倾向导致相对于1，1-碳硼化更低的1，2-碳硼化势垒。
The reaction of 8-(trimethylsiloxy)quinoline (QOTMS) with BCl3 and (aryl)BCl2 forms QOBCl2 and QOBCl(aryl). The subsequent addition of stoichiometric AlCl3 follows one of two paths, dependent on the steric demands of the QO ligand and the electrophilicity of the resulting borenium cation. The phenyl- and 5-hexylthienylborenium cations, QOBPh+ and QOBTh+, are formed, whereas QOBCl+ is not. Instead, AlCl3 preferentially binds with QOBCl2 at oxygen, forming QOBCl2⋅AlCl3, rather than abstracting chloride. A modest increase in the steric demands around oxygen, by installing a methyl group at the 7-position of the quinolato ligand, switches the reactivity with AlCl3 back to chloride abstraction, allowing formation of QOBCl+. All the prepared borenium cations are highly chlorophilic and exhibit significant interaction with AlCl4− resulting in an equilibrium concentration of Lewis acidic “AlCl3” species. The presence of “AlCl3” species limits the alkyne substrates compatible with these borenium systems, with reaction of [QOBPh][AlCl4] with 1-pentyne exclusively yielding the cyclotrimerised product, 1,3,5-tripropylbenzene. In contrast, QOBPh+ and QOBTh+ systems effect the syn-1,2-carboboration of 3-hexyne. DFT calculations at the M06-2X/6-311G(d,p)/PCM(DCM) level confirm that the higher migratory aptitude of Ph versus Me leads to a lower barrier to 1,2-carboboration relative to 1,1-carboboration.
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影响因子：
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