Issue 6, 2014

Cycloaddition of CO2 and epoxides catalyzed by imidazolium bromides under mild conditions: influence of the cation on catalyst activity

Abstract

The synthesis and characterization of a library of imidazolium-based compounds of the type [R1R2R3im]Br (R1 = H, CH3, benzyl (Bz), 1-(2,3,4,5,6-pentafluoro)benzyl (BzF5); R2 = H, CH3, C2H5; R3 = n-butyl, n-octyl) are reported. All compounds were characterized by means of 1H and 13C NMR spectroscopy, elemental analysis and single crystal X-ray diffraction in the case of 1-BzF5-3-n-octylimidazolium bromide and examined as catalysts for the cycloaddition of carbon dioxide and propylene oxide (PO) to yield propylene carbonate (PC). The catalyst screening shows the influence of different substituents (steric and ion pairing effects) on the catalytic activity. It is shown that the most active catalyst, 1-BzF5-3-n-octylimidazolium bromide (10), gives very good conversions and carbonate yields at 70 °C and below 5 bar CO2 pressure, which is the lowest temperature for the synthesis of PC from PO and CO2 using metal-free catalysts. Catalyst 10 can be recycled and reused at least 10 times without loss of yield and activity.

Graphical abstract: Cycloaddition of CO2 and epoxides catalyzed by imidazolium bromides under mild conditions: influence of the cation on catalyst activity

Supplementary files

Article information

Article type
Paper
Submitted
07 Dec 2013
Accepted
17 Feb 2014
First published
17 Feb 2014

Catal. Sci. Technol., 2014,4, 1749-1758

Cycloaddition of CO2 and epoxides catalyzed by imidazolium bromides under mild conditions: influence of the cation on catalyst activity

M. H. Anthofer, M. E. Wilhelm, M. Cokoja, I. I. E. Markovits, A. Pöthig, J. Mink, W. A. Herrmann and F. E. Kühn, Catal. Sci. Technol., 2014, 4, 1749 DOI: 10.1039/C3CY01024D

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