合成了低聚乙二醇取代的咪唑鎓盐作为一系列S N 2反应的促进剂,并检查了它们的效率。这些量身定制的有机促进剂通过两个促进剂(低聚乙二醇和咪唑鎓盐)在单个分子中的联合作用,显着增强了碱金属盐的亲核性。系统研究了低聚乙二醇侧链长度,离子液体阴离子,亲核试剂和底物的影响。[hexaEGmim] [OMs]和[dihexaEGim] [OMs]显示了使用碱金属盐进行S N 2反应的最高效率。通过检查相对S N来评估低聚乙二醇部分的末端羟基基团的作用2氯化和溴化收率。结果表明,羟基与亲核试剂的氢键强度非常重要。通过量子化学计算研究了oligoEGILs促进S N 2反应的优异机理。结果表明,低聚乙二醇部分中的氧原子和离子液体阴离子作为路易斯碱作用于抗衡阳离子K +或Na +上,从而显着提高了金属盐的反应性。
An efficient and chemoselective deprotection of tert-butyldimethylsilyl (TBDMS) ethers using tailor-made ionic liquid
摘要:
Phenolic tert-butyldimethylsilyl (TBDMS) ethers can be deprotected to yield phenols in excellent yield using tailor-made ionic liquid [dihexaEGim][OMs] (dihexaEGim = dihexaethylene glycolic imidazolium salt) as an organic catalyst with alkali-metal fluoride in tert-amyl alcohol. On the contrary, all TBDMS protecting groups can be cleaved cleanly from the bis-TBDMS ether using the same reaction in CH3CN solvent instead of tert-alcohol at 100 degrees C. This [dihexaEGim][OMs]/tert-amyl alcohol media system allows the highly selective phenolic deprotection reaction of various bis-TBDMS ethers containing both phenolic and aliphatic TBDMS ethers to provide the corresponding phenols in high yield. (C) 2012 Elsevier Ltd. All rights reserved.
Tailor-Made Hexaethylene Glycolic Ionic Liquids as Organic Catalysts for Specific Chemical Reactions
作者:Vinod H. Jadhav、Hwan-Jeong Jeong、Seok Tae Lim、Myung-Hee Sohn、Dong Wook Kim
DOI:10.1021/ol200751e
日期:2011.5.6
Hexaethylene glycol substituted imidazolium based ionicliquids (hexaEGILs) were designed and prepared well-tailored to a specific organic reaction using alkali-metal fluorides (MFs) as multifunctional organic catalysts. These hexaEGIL catalysts could significantly enhance the reactivity of MF, even KF. Furthermore, the hexaEGIL systems showed tremendous efficiency in the nucleophilicfluorination of base-sensitive