Synthesis of new 5-substituted pyrazolo[1,5-d][1,2,4]-triazine derivatives and their analgesic, anti-inflammatory and antipyretic properties.

A series of 2-aryl-4-oxo-pyrazolo[1,5-d][1,2,4]triazines substituted in the 5-position by aminoalkyl or benzoyl moieties was synthesized and evaluated for analgesic activity. The structures of new triazine derivatives were confirmed by IR, 1H-NMR spectra and by elementary analysis. In the phenylbenzoquinone induced writhing test, only 3,3a-dihydropyrazolo triazines substituted by an arylpiperazinylmethyl group exhibited potent analgesic effect. In addition, these compounds possessed significant anti-inflammatory and antipyretic properties. A desaturation in 3,3a positions or other groups than arylpiperazinylmethyl moieties notably decreased analgesic effects.