One-Pot Wittig and Knoevenagel Reactions in Ionic Liquid as Convenient Methods for the Synthesis of Coumarin Derivatives |
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Authors: | Hassan Valizadeh Sevil Vaghefi |
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Affiliation: | 1. Faculty of Science, Department of Chemistry , Azerbaijan University of Tarbiat-Moallem , Tabriz, Iran h-valizadeh@azaruniv.edu;3. Faculty of Science, Department of Chemistry , Azerbaijan University of Tarbiat-Moallem , Tabriz, Iran |
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Abstract: | Efficient synthesis of a variety of 3-substituted coumarins via NaOMe-catalyzed Knoevenagel condensation and one-pot preparation of 3,4-unsubstituted coumarins in the presence of NaOMe via Wittig reaction in room-temperature ionic liquids are described. Knoevenagel condensation of 2-hydroxybenzaldehyde with dimethyl- and diethylmalonate was performed with excellent yields in room-temperature ionic liquids. Although diethyl- and dimethylchloromalonates were mostly recovered unchanged in Knoevenagel condensation, higher conversions were observed via Wittig reaction of these compounds with 2-hydroxybenzaldehyde derivatives and triphenylphosphine. Other 2-hydroxybenzaldehyde derivatives, methyl- and ethylchloroacetates, were reacted in ionic liquids to afford simple coumarins in good yields. These reactions widen the applicability of ionic liquid in organic synthesis. |
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Keywords: | Coumarins ionic liquid Knoevenagel reaction Wittig reaction |
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