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Knoevenagel Reaction in [MMIm][MSO4]: Synthesis of Coumarins
Department of Organic Chemistry, Faculty of Chemistry, University of Vigo, 36310 Vigo, Spain
* Author to whom correspondence should be addressed.
Received: 26 April 2011; in revised form: 18 May 2011 / Accepted: 19 May 2011 / Published: 27 May 2011
Abstract: 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.
Keywords: ionic liquid; Knoevenagel reaction; synthesis; coumarins
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Verdía, P.; Santamarta, F.; Tojo, E. Knoevenagel Reaction in [MMIm][MSO4]: Synthesis of Coumarins. Molecules 2011, 16, 4379-4388.
Verdía P, Santamarta F, Tojo E. Knoevenagel Reaction in [MMIm][MSO4]: Synthesis of Coumarins. Molecules. 2011; 16(6):4379-4388.
Verdía, Pedro; Santamarta, Francisco; Tojo, Emilia. 2011. "Knoevenagel Reaction in [MMIm][MSO4]: Synthesis of Coumarins." Molecules 16, no. 6: 4379-4388.