Recyclable polymeric ionic liquids applied as metal-free transfer hydrogenation catalysts

IF 0.8 4区 化学 Q4 CHEMISTRY, MULTIDISCIPLINARY
G. Dhimba, M. Bala
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引用次数: 0

Abstract

A new methodology for immobilizing a triazolium salt onto polyethylene glycols (PEG) was developed. The immobilization is a two-step reaction, involving the tosylation of PEGs followed by a neat reaction between the PEG tosylates and the triazole. It is a high-yielding reaction conducted under mild conditions with a simple workup procedure. Hence, the salt 1-benzyl-4-phenyl-1H-1,2,3-triazolium iodide was immobilised onto PEGs of varying chain lengths (PEG300_8000) to yield various polymeric ionic liquids (PILs). All the PIL compounds were characterised by spectroscopic analysis and utilised as homogeneous metal-free organocatalysts for the transfer hydrogenation of ketones to alcohols in isopropanol as solvent and hydrogen source. The metal-free PIL catalysts showed activity for transforming acetophenone to 1-phenyl alcohol at up to 87% conversion. The representative PEG600 system was recycled three times with minimal loss in activity. The mechanism of a possible catalyst leaching was investigated using computational calculations. The results reveal that the promoter, isopropanol, also promotes the leaching of the triazole from the PEG backbone.
可回收聚合物离子液体用作无金属转移加氢催化剂
提出了一种三唑盐在聚乙二醇(PEG)上固定的新方法。固定化是一个两步反应,包括聚乙二醇的甲酰基化,然后是聚乙二醇甲酰基酸酯和三唑之间的整齐反应。这是一个在温和条件下进行的高收率反应,后处理程序简单。因此,将1-苄基-4-苯基- 1h -1,2,3-碘化三唑盐固定在不同链长的聚乙二醇(PEG300_8000)上,得到各种聚合物离子液体(PILs)。所有的PIL化合物都通过光谱分析进行了表征,并用作均相无金属有机催化剂,用于在异丙醇作为溶剂和氢源的情况下酮类转化为醇的氢化反应。无金属PIL催化剂将苯乙酮转化为1-苯醇的转化率高达87%。具有代表性的PEG600体系回收了三次,活动损失最小。用计算方法研究了一种可能的催化剂浸出机理。结果表明,促进剂异丙醇也能促进三唑从PEG主链中浸出。
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来源期刊
CiteScore
3.10
自引率
0.00%
发文量
6
审稿时长
>12 weeks
期刊介绍: Original work in all branches of chemistry is published in the South African Journal of Chemistry. Contributions in English may take the form of papers, short communications, or critical reviews.
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