One-pot synthesis of carbazole based 3-hydroxy-4H-chromen-4-ones by a modified Algar-Flynn-Oyamada reaction and their antimicrobial activity

A new series of 2-(9-ethyl-9H-carbazol-3-yl)-3-hydroxy-4H-chromen-4-ones were synthesized from substituted 2-hydroxyacetophenones and 9-ethyl-9H-carbazole-3-carbaldehyde using NaOH and H2O2 by a modified Algar-Flynn-Oyamada reaction. In this method, the flavonols were synthesized in good yields (70-82 %) without isolating chalcones. The structures of the compounds were established based on H-1-NMR, C-13-NMR, FT-IR and mass spectral and analytical data. All the compounds were evaluated for their antimicrobial activity against bacteria, such as Staphylococus aureus, Bacillus subtilis, Escherichia coli and Klebsiella pneumoniae, as well as fungi, such as Aspergillus flavus and Fusarium oxysporum.