Several 6- and 7-alkoxy-2-oxo-2H-chromene-4-carbaldehydes were prepared
from corresponding alkyl ethers of 6- and 7-hydroxy-4-methyl-2-oxo-2H-chromen-2-ones
by oxidation using selenium dioxide. 6- and 7-Alkoxy-4-methyl-2H-chromenes were obtained
with yields of 57-85%. Corresponding 4-carbaldehyde derivatives were prepared
with yields of 41-67%. Thiosemicarbazones of these aldehydes with D-galactose moiety
were synthesized by reaction of these aldehydes with N-(2,3,4,6-tetra-O-acetyl-β-Dgalactopyranosyl)
thiosemicarbazide with yields of 62-74%. These thiosemicarbazones
were screened for their antibacterial and antifungal activities in vitro against bacteria, such
as Staphylococcus aureus, Escherichia coli, and fungi, such as Aspergillus niger, Candida
albicans. Several compounds exhibited strong inhibitory activity with MIC values of 0.78-
1.56 μM, including 8a (against S. aureus, E. coli, and C. albicans), 8d (against E. coli and A. niger), 9a
(against S. aureus), and 9c (against S. aureus and C. albicans).
Selenium Dioxide-Mediated Bromination of α,β-Unsaturated Ketones Using N-Bromosuccinimide in the Presence of p-Toluenesulfonic Acid: A Versatile Route for the Synthesis of α′-Bromo-4-arylbut-3-en-2-one and α′,α′-Dibromo-4-arylbut-3-en-2-one
