Functionalisation of the nido-dicarbaborate anion nido-7,8 by hydride abstraction

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• 作者：Ren茅 Frank ; Henry Auer ; Evamarie Hey-Hawkins
• 关键词：nido-7 ; 8-C2B9H12&minus ; Water-free hydride abstraction ; Symmetric EINS-type reaction ; Asymmetric electrophilic substitution ; Charge compensation
• 刊名：Journal of Organometallic Chemistry
• 出版年：1 December, 2013
• 年：2013
• 卷：747
• 期：Complete
• 页码：217-224
• 全文大小：1568 K

文摘

Substitution at the dicarbaborate anion nido-7,8聽(1) with precise hydride abstraction leads to symmetric products 10-R-nido-7,8-C₂B₉H₁₁, e.g., 10-[cyclo-(CH₂)₄O]-nido-7,8-C₂B₉H₁₁ (2) and 10-[cyclo-(CH₂)₄S]-nido-7,8-C₂B₉H₁₁ (3). However, this approach has been limited to acetaldehyde as hydride acceptor in an acidified, aqueous two-phase system. In expanding the concept of hydride abstraction, we have found that acetone, activated by AlCl₃, is capable of accepting hydride with substitution of the symmetric B10 position in the presence of suitable donor molecules (Lewis bases). Thus, by employing a one-phase water-free system, 2 and 3 as well as moisture-sensitive 10-CH₃CN-nido-7,8-C₂B₉H₁₁ (4) were obtained in good to high yield. Reactions with 1 in neat acetone gave 10-HO-nido-7,8聽(7). An alternative reagent for hydride abstraction in 1 is tritylium tetrafluoroborate (Ph₃CBF₄), which gave 10-Ph₂S-nido-7,8-C₂B₉H₁₁ (11) in the presence of Ph₂S. The Ph₂S moiety in 11 could easily be replaced by pyridine and triethylamine, giving 10-C₅H₅N-nido-7,8-C₂B₉H₁₁ (12) and 10-Et₃N-nido-7,8-C₂B₉H₁₁ (13). Additionally, reactions of 1 with CF₃SO₃H in the presence of CH₃CN or CH₃SCN gave 9-CH₃C(NH₂)-nido-7,8-C₂B₉H₁₁ (5) and 9-CH₃SC(NH₂)-nido-7,8-C₂B₉H₁₁ (6) by electrophilic substitution.