Brönsted acid ionic liquid-catalyzed direct benzylation, allylation and propargylation of 1,3-dicarbonyl compounds with alcohols as well as one-pot synthesis of 4H-chromenes |
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Authors: | Kazumasa Funabiki Takuya Komeda Yasuhiro Kubota Masaki Matsui |
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Institution: | Department of Materials Science and Technology, Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan |
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Abstract: | Recyclable ionic Brönsted acid was prepared in nearly quantitative yield by reacting 1-butylimidazole with an equimolar amount of 1,3-propanesultone, followed by treatment with an equimolar amount of trifluoromethanesulfonic acid. The ionic Brönsted acid-catalyzed direct benzylation, allylation and propargylation of 1,3-dicarbonyl compounds with various alcohols in ionic liquid N-ethyl-N-methyl imidazolium trifluoromethanesulfonate (EMIOTf)], at 100 °C for 3 h proceeded smoothly to give the corresponding products in good to excellent yields without the use of any hazardous or volatile solvents and without any by-product such as salts. Furthermore, tandem benzylation-cyclization-dehydration of 1,3-dicarbonyl compounds to give functionalized 4H-chromenes was also achieved in this catalytic reaction. |
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Keywords: | Ionic Brö nsted acid catalyst Substitution 1 3-Dicarbonyl compounds Alcohol |
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