Sequential Camouflage of the arachno-6,9-C2B8H14 Cage by Substituents

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• 作者：Mario Bakardjiev ; Bohumil Štíbr ; Josef Holub ; Oleg L. Tok ; Petr Švec ; Zdeňka Růžičková ; Aleš Růžička
• 刊名：Inorganic Chemistry
• 出版年：2016
• 出版时间：July 18, 2016
• 年：2016
• 卷：55
• 期：14
• 页码：7068-7074
• 全文大小：444K
• 年卷期：0
• ISSN：1520-510X

文摘

Sequential methylation of arachno-6,9-C₂B₈H₁₄ (1) led to a series of methyl derivatives and finally to the camouflaging of all boron positions by mixed persubstitution. Thus, deprotonation of 1 produced the [arachno-6,9-C₂B₈H₁₃] anion (1^–), the methylation of which with MeI in tetrahydrofuran proceeded on the open-face boron vertexes with the formation of 5-Me-arachno-6,9-C₂B₈H₁₃ (2; yield 28%) and 5,8-Me₂-arachno-6,9-C₂B₈H₁₂ (3; yield 36%). Observed in this reaction was also a side formation of 2-Me-closo-1,6-C₂B₈H₉ (4; yield 6%).The electrophilic AlCl₃-catalyzed CH₃⁺ attack of the neutral 1 in neat MeI at ambient temperature afforded 1,3-Me₂-arachno-6,9-C₂B₈H₁₂ (5), while a 76-h heating at 120 °C generated a mixture of the di- and triiodo derivatives 1,2,3,4,8,10-Me₆-5,7-I₂-arachno-6,9-C₂B₈H₆ (6) and 1,2,3,4,7-Me₅-5,7,10-I₃-arachno-6,9-C₂B₈H₆ (7). On the other hand, a HOTf-catalyzed reaction between 1 and MeOTf at reflux resulted in the isolation of 2-TfO-1,3.4,5,7,8,10-Me₇-arachno-6,9-C₂B₈H₆ (8; Tf = CF₃SO₂; yield 65%). The compounds were characterized by multinuclear (¹¹B, ¹H, ¹³C, and ¹⁹F) NMR spectroscopy, mass spectrometry, and elemental analysis, and the structures of compounds 1, 1^–, 5, and 6 were established by X-ray diffraction analysis.