The CNS stimulation study has been performed on the two semisynthetic adducts of caffeine with Schiff?s base of pyrazolone and pyrazolone-pyrimidine nucleus. All the reference drugs and test compounds showed positive effect on CNS stimulation. The conclusion has been drawn from the fact that CNS stimulation effect for pentylene tetrazole is higher than caffeine, compound-I (pyrazolone ring) is less active than compound-II as the compound-II (pyrazolo-pyrimidine ring) is fused ring heterocyclic compound and the synergistic action with caffeine with compound-I having less activity than the compound-II but in case of leptazol (pentylene tetrazole), the synergistic activity of the two test compounds are equal but less than leptazol itself. The azole group is present in both caffeine and in leptazol but in fused ring heterocyclic chromophore and the same ring has been implemented in the two test compounds which have been semisynthesized by formation of Schiff?s base of caffeine to keep the similar bioisosteric nature. So, the components that have been semisynthesized showed the specific CNS stimulation activity.