Resumen de Synthesis of 8-hydroxyquinoline chalcones: Trans configuration, intramolecular hydrogen bonds, bromination, and antifungal activity
Alonso J Marrugo-gonzález, Valerie D Orlov, Roberto Fernández-Maestre
Nine (8-Hydroxyquinolin-5-yl)-arylpropenones were synthesized and their structures demonstrated by IR and NMRspectroscopy. These molecules showed transconfiguration and strong intramolecular hydrogen bonding; in the IR spectra of 5-formyl-8-hydroxyquinoline, 5-acetyl-8-hydroxyquinoline, 1-(8-hydroxyquinolin-5-yl)-3-phenylprop-2-en-1-one and 3-(8-hydroxyquinolin-5-yl)-1-phenylprop-2-en-1-one in CHCl3, besides the known intermolecular hydrogen band (~3180 cm-1), we identified the intramolecular hydrogen band OH-N (3460 cm-1); the hydrogen bond peaks shifted to low frequency in proton-donor solutions such as phenol and acetic acid (with respect to 8-hydroxyquinoline) and the bonds were broken in trifluoroacetic acid solutions, due to OH protonation; the apolar solvent CCl4 and electrophilic substituents in position 5 in the quinoline ring, limited the formation of the intermolecular hydrogen bonds and, therefore, shifted the ~3460 cm-1 intramolecular hydrogen band to lower frequencies and made it stronger and sharper. The bromination of 3-(8-hydroxyquinolin-5-yl)-1-(4-tolyl) prop-2-en-1-one occurred on the activated quinoline fragment, producing monobromo and tetrabromo derivatives, instead of bromination on the aliphatic double bond. Three chalcones tested showed strong antifungal activity in vitro.
