Molecules (May 2011)

Knoevenagel Reaction in [MMIm][MSO4]: Synthesis of Coumarins

  • Emilia Tojo,
  • Francisco Santamarta,
  • Pedro Verdía

DOI
https://doi.org/10.3390/molecules16064379
Journal volume & issue
Vol. 16, no. 6
pp. 4379 – 4388

Abstract

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The ionic liquid 1,3-dimethylimidazolium methyl sulfate, [MMIm][MSO4], together with a small amount of water (the amount taken up by the ionic liquid upon exposure to air), acts efficiently as both solvent and catalyst of the Knoevenagel condensation reactions of malononitrile with 4-substituted benzaldehydes, without the need for any other solvent or promoter, affording yields of 92%–99% within 2–7 min at room temperature. When L-proline is used as an additional promoter to obtain coumarins from o-hydroxybenzaldehydes, the reaction also proceeds in high yields. Work-up is very simple and the ionic liquid can be reused several times. Some of the coumarins obtained are described for the first time.

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