Hydrogen-bond-rich ionic liquids as effective organocatalysts for Diels-Alder reactions

Karol Erfurt, Ilona Wandzik, Krzysztof Walczak, Karolina Matuszek, Anna Chrobok

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Abstract

The synthesis and characterisation of new hydrogen-bond-rich ionic liquids and studies of their catalytic performance in Diels-Alder reactions are described. d-Glucose and chloroalcohols were used as the raw materials and as the sources of hydroxyl groups for the synthesis of ionic-liquid cations, whereas weakly coordinating bis(trifluoromethylsulfonyl)imide was used as the anion. The new ionic liquids were analysed by 1H and 13C NMR spectroscopy and by ESI-MS experiments, which confirmed their structures. In addition, the thermal data of the studied ionic liquids measured by differential scanning calorimetry and thermogravimetric analysis showed that these compounds tend to form a glass at temperatures in the range of -29°C to -16°C and are thermally stable from ambient temperature to at least 430°C, most likely because of the presence of bis(trifluoromethylsulfonyl) imide anions. The performance of the ionic liquids in the model reaction of cyclopentadiene with diethyl maleate or methyl acrylate was investigated. The studied ionic liquids showed high activity even when present in catalytic amounts (4 mol% with respect to the dienophile). An increase in the number of hydroxyl groups present in the ionic liquid structure resulted in higher reaction rates. This journal is

Original languageEnglish
Pages (from-to)3508-3514
Number of pages7
JournalGreen Chemistry
Volume16
Issue number7
DOIs
Publication statusPublished - 1 Jan 2014
Externally publishedYes

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