Heterocyclic compounds based on 3-(4-bromophenyl) azo-5-phenyl-2(3H)-furanone: anti-avian influenza virus (H5N1) activity.

1 3-[2-(4-Bromphenyl)hydrazono]-5-phenyl-furan-2(3H)-one () was used for preparation of some novel pyrazole, pyridazinone, oxadiazole, triazole, thiazolidine and thioxopyrimidine derivatives. Some of the prepared products were tested for anti-avian influenza virus activity and revealed promising antiviral activity against H5N1 virus [A/Chicken/Egypt/1/20 % (H5N1)] by determination of both EC50 and LD50 and confirmed by plaque reduction assay on Madin-Darby canine kidney cells. Compounds 3-[2-(4-bromophenyl)hydrazono]-5-phenylfuran-2(3H)-one (1), 1-(4-bromophenyl)-N-hydroxy-5-phenyl-1H-pyrazole-3-carboxamide (5) and 1-(4-bromophenyl)-N-{2,3-dihydro-4-hydroxy-3-phenyl-6-oxo-2-thioxopyrimidin-1(6H)-yl}-5-phenyl-1H-pyrazole-3-carboxamide (12a) showed the highest effects. Detailed synthesis, spectroscopic data, and antiviral activity of the synthesized compounds are reported.