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

作者：Xu, Cuilian^*; Yang, Guoyu; Wang, Caixia; Fan, Sufang; Xie, Lixia; Gao, Ya

来源：Molecules, 2013, 18(10): 11964-11977.

DOI：10.3390/molecules181011964

• solvent-free
• 2-hydroxy-2-(trifluoromethyl)-2H-chromene-3-carboxylates
• synthesis
• Knoevenagel condensation
• silica-immobilized L-proline

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, H-1-NMR, C-13-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.

• 出版日期2013-10
• 单位河南农业大学