Journal
TETRAHEDRON
Volume 65, Issue 36, Pages 7457-7463Publisher
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.tet.2009.07.012
Keywords
Ionic Bronsted acid catalyst; Substitution; 1,3-Dicarbonyl compounds; Alcohol
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Funding
- New Energy and Industrial Technology Development Organization of Japan (NEDO)
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Recyclable ionic Bronsted 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 Bronsted 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 degrees 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. (C) 2009 Elsevier Ltd. All rights reserved.
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