Ionic Liquids as Green Solvents for the Oxidation of Alcohols

Shirini, Farhad; Abedini, Masoumeh; Atghia, Seyyed Vahid

doi:10.1007/978-94-007-2891-2_14

Cited by 2 publications

(2 citation statements)

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“…Ionic liquids represent a valuable solvent class that can overcome solvent safety issues related to flammability and low vapor pressure, making them very attractive for oxidation reactions. − Moreover, we observe that the sublimation properties of DFF are retained in the ionic liquid and that the molecule can be easily separated under vacuum at relatively low temperature (80 °C) to provide a high purity product . The selective oxidation of alcohols in ionic liquids has been studied widely, and various systems based mostly on homogeneous catalysts have been proposed. , It is usually considered that aerobic oxidation is the most environmentally friendly oxidation technique for these transformations, since oxygen (at low pressures) is relatively cheap and safe. Stoichiometric oxidants can produce toxic waste or introduce a large amount of water into the system, which can compromise the selectivity and yield of the reaction.…”

Section: Introductionmentioning

confidence: 94%

“…25 The selective oxidation of alcohols in ionic liquids has been studied widely, and various systems based mostly on homogeneous catalysts have been proposed. 41,42 It is usually considered that aerobic oxidation is the most environmentally friendly oxidation technique for these transformations, since oxygen (at low pressures) is relatively cheap and safe. Stoichiometric oxidants can produce toxic waste or introduce a large amount of water into the system, which can compromise the selectivity and yield of the reaction.…”

Section: ■ Introductionmentioning

confidence: 99%

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Efficient Formation of 2,5-Diformylfuran in Ionic Liquids at High Substrate Loadings and Low Oxygen Pressure with Separation through Sublimation

Ghatta

Wilton‐Ely

Hallett

2020

ACS Sustainable Chem. Eng.

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The oxidation of 5-hydroxymethylfurfural (HMF) to 2,5-diformylfuran (DFF) using oxygen (1 atm) with a TEMPO and CuCl catalyst system is investigated using a range of imidazolium-based ionic liquids (ILs) and various bases at different HMF substrate loadings (10-50%). This represents the first example of HMF to DFF conversion in ionic liquid media under homogeneous catalysis conditions, revealing dramatic differences in performance between the ILs. In the non-coordinating, hydrophobic ionic liquid, [bmim][NTf2], 90% DFF yield is obtained at 5 mol% catalyst loading after 6 hours at 80 °C at a very high 40% HMF loading. Increasing the temperature to 100 °C leads to a lower yield, attributed to loss of volatile TEMPO from the reaction medium. A system using TEMPO and pyridine immobilized within the ionic liquid [bmim][NTf2] results in selective conversion of HMF to high purity DFF. It also allows the DFF formed to be isolated by sublimation in 81% yield before a further cycle is performed. Subsequent catalyst deactivation is probed by X-ray photoelectron spectroscopy (XPS). Synthesis from fructose in a two-step process achieves a 55% isolated DFF yield. This approach overcomes significant drawbacks previously reported for this transformation, such as solvent toxicity, separation and purification problems as well as the need for high oxygen pressures. Further oxidation of HMF with this system leads to a 62% yield of 5-formyl-2furancarboxylic acid (FFCA). The separation of this compound can be achieved by sublimation of DFF followed by solvent extraction.

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