3-(1,3-diphenylpyrazol-4-yl-methylene)-5-aryl-2(3H)-furanones 2 were prepared and converted into a variety of heterocyclic systems of synthetic and biological importance. Benzylamine reacted with the furanones 2; the product was found to depend on the reaction conditions. Thus, at room temperature the open-chain N-benzylamides 3 were obtained, whereas under refluxing conditions the 2(3H)-pyrrolones were obtained. Hydrazine hydrate affected ring opening of the furanones to give the corresponding acid hydrazides 5. The latter products were used as key starting materials for the synthesis of pyridazinones 7 and 8, 1,3,4-oxadiazoles 11 and 13 and 1,2,4-triazoles 12 and 14 all bearing pyrazolyl moiety as a side-chain. Evaluation of antiviral activity of selected examples of the compounds obtained was performed using two viruses: HAV and HSV-1. Some of the tested compounds showed promising activities.