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.
离子液体1,3-二甲基
咪唑鎓甲基
硫酸盐[MMIm][MSO4]以及少量
水(与空气接触时被
离子液体吸收的
水量)有效地作为溶剂和催化剂,实现了
丙二腈与4-取代
苯甲醛的Knoevenagel缩合反应,无需任何其他溶剂或
促进剂,在室温下实现了92%–99%的高产率,反应时间为2–7分钟。当使用
L-脯氨酸作为额外
促进剂从邻羟基
苯甲醛合成
香豆素时,反应同样获得了高产率。后处理非常简单,
离子液体可以重复使用多次。一些所获得的
香豆素首次被描述。