A series of -4-phthalimido-4,5-dihydro-1H-1,2,4-triazol-5-ones (3) wer
e obtained from the reactions of (aryl)-4-amino-4,5-dihydro-1H-1,2,4-t
riazol-5-ones (1) with phthalic anhydride via intermediate benzoic aci
d derivatives 2. IR, H-1-NMR, C-13-NMR and UV spectral data of new com
pounds have been presented and discussed.