Imidazolium Sulfonates as Environmental-Friendly Catalytic Systems for the Synthesis of Biologically Active 2-Amino-4H-chromenes: Mechanistic Insights
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- 作者：Jacinto Velasco ; Elena P茅rez-Mayoral ; Vanesa Calvino-Casilda ; Antonio J. L贸pez-Peinado ; Miguel A. Ba帽ares ; Elena Soriano
- 刊名：Journal of Physical Chemistry B
- 出版年：2015
- 出版时间：September 10, 2015
- 年：2015
- 卷：119
- 期：36
- 页码：12042-12049
- 全文大小：429K
- ISSN：1520-5207
文摘
Ionic Liquids (ILs) are valuable reaction media extremely useful in industrial sustainable organic synthesis. We describe here the study on the multicomponent reaction (MCR) between salicylaldehyde (2) and ethyl cyanoacetate (3), catalyzed by imidazolium sulfonates, to form chromenes 1, a class of heterocyclic scaffolds exhibiting relevant biological activity. We have clarified the reaction mechanism by combining the experimental results with computational studies. The results reported herein suggest that both the imidazolium core and the sulfonate anions in the selected ILs are involved in the reaction course acting as hydrogen bond donors and acceptors, respectively. Contrarily to the most widely accepted mechanism through initial Knoevenagel condensation, the most favorable reaction pathway consists of an aldolic reaction between reagents followed by heterocyclization, subsequent dehydration, and, finally, the Michael addition of the second molecule of ethyl cyanoacetate (3) to yield the chromenes 1.