An efficient solvent-free synthesis of 2-hydroxy-2-(trifluoromethyl)-2H-chromenes using 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, 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.
School of Science, Henan Agricultural University, Zhengzhou 450002, China.. xucuilian666@126.com.
Cuilian
C
Xu
Guoyu
G
Yang
Caixia
C
Wang
Sufang
S
Fan
Lixia
L
Xie
Ya
Y
Gao
D000447:Aldehydes / Q000737:chemistry; D001578:Benzopyrans / Q000138:chemical synthesis*; D002384:Catalysis; D018360:Crystallography, X-Ray; D005463:Fluoroacetates / Q000737:chemistry; D055772:Green Chemistry Technology; D008958:Models, Molecular; D008968:Molecular Conformation; D011392:Proline / Q000737:chemistry*; D012822:Silicon Dioxide / Q000737:chemistry*; D060327:Solid-Phase Synthesis Techniques; D012997:Solvents / Q000737:chemistry
D000447:Aldehydes; D001578:Benzopyrans; D005463:Fluoroacetates; D012997:Solvents; C013243:salicylaldehyde; D012822:Silicon Dioxide; D011392:Proline