Molecules 2013, 18(10), 11964-11977; doi:10.3390/molecules181011964
Article

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

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Received: 15 July 2013; in revised form: 7 September 2013 / Accepted: 11 September 2013 / Published: 26 September 2013
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract: 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.
Keywords: solvent-free; 2-hydroxy-2-(trifluoromethyl)-2H-chromene-3-carboxylates; synthesis; Knoevenagel condensation; silica-immobilized L-proline
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MDPI and ACS Style

Xu, C.; Yang, G.; Wang, C.; Fan, S.; Xie, L.; Gao, Y. An Efficient Solvent-Free Synthesis of 2-Hydroxy-2-(trifluoromethyl)-2H-chromenes Using Silica-Immobilized L-Proline. Molecules 2013, 18, 11964-11977.

AMA Style

Xu C, Yang G, Wang C, Fan S, Xie L, Gao Y. An Efficient Solvent-Free Synthesis of 2-Hydroxy-2-(trifluoromethyl)-2H-chromenes Using Silica-Immobilized L-Proline. Molecules. 2013; 18(10):11964-11977.

Chicago/Turabian Style

Xu, Cuilian; Yang, Guoyu; Wang, Caixia; Fan, Sufang; Xie, Lixia; Gao, Ya. 2013. "An Efficient Solvent-Free Synthesis of 2-Hydroxy-2-(trifluoromethyl)-2H-chromenes Using Silica-Immobilized L-Proline." Molecules 18, no. 10: 11964-11977.

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