An Efficient Solvent-Free Synthesis of 2-Hydroxy-2-(trifluoromethyl)-2H-chromenes Using Silica-Immobilized L-Proline

Molecules

Cuilian Xu¹  Guoyu Yang²  Caixia Wang²  Sufang Fan²  Lixia Xie² 

[1] School of Science, Henan Agricultural University, Zhengzhou 450002, China;

关键词: solvent-free;    2-hydroxy-2-(trifluoromethyl)-2H-chromene-3-carboxylates;    synthesis;    Knoevenagel condensation;    silica-immobilized L-proline;   

DOI  :  10.3390/molecules181011964

来源: mdpi

【 摘 要 】

An efficient synthesis of 2-hydroxy-2-(trifluoromethyl)-2H-chromene-3-carboxylates was carried out under solvent-free conditions in an oven or microwave oven via the Knoevenagel condensation of salicylaldehydes with ethyl trifluoroacetoacetate followed by intramolecular cyclization in the presence of silica-immobilized L-proline. The structures of the title compounds were characterized by IR, ¹H-NMR, ¹³C-NMR, HRMS and X-ray single crystal diffraction. The improved method described herein is economical, easily-operated and environmentally friendly. Furthermore, the catalyst can be recovered conveniently and reused without obvious loss of activity.

【 授权许可】

CC BY   
© 2013 by the authors; licensee MDPI, Basel, Switzerland.