{"title":"Recyclable polymeric ionic liquids applied as metal-free transfer hydrogenation catalysts","authors":"G. Dhimba, M. Bala","doi":"10.17159/0379-4350/2022/v76a17","DOIUrl":null,"url":null,"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.","PeriodicalId":49495,"journal":{"name":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","volume":null,"pages":null},"PeriodicalIF":0.8000,"publicationDate":"2022-12-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"South African Journal of Chemistry-Suid-Afrikaanse Tydskrif Vir Chemie","FirstCategoryId":"92","ListUrlMain":"https://doi.org/10.17159/0379-4350/2022/v76a17","RegionNum":4,"RegionCategory":"化学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q4","JCRName":"CHEMISTRY, MULTIDISCIPLINARY","Score":null,"Total":0}
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.
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.