Synthesis, Analgesic and Anti-inflammatory Activities of Some Pyrazolo[3,4-c]pyrazole Derivatives

Historically, heterocyclic compounds containing Nitrogen, and their derivatives have been invaluable as a source of therapeutic agents. Pyrazole, with two nitrogen atoms and aromatic character, provides diverse functionality and stereochemical complexity in a five-membered ring structure. In Knorr pyrazole synthesis, diimine compound gets deprotonated to regenerate the acid catalyst and provide the final pyrazole product. Formation of pyrazole derivatives from hydrazines, hydrazides, semicarbazides, thiosemicarbazide and aminoguanidines by condensation with 1,3-dicarbonyl compounds is possible. As fused pyrazoles are reported to be well known pharmacophores, this has motivated to synthesize some of the pyrazolopyrazole derivatives by using hydrazine hydrate, thiosemicarbazide and semicarbazide. A series of 3-(aryl)-4-methyl-3a,6-dihydropyrazolo[3,4-c]pyrazole-2(3H)-carboxamides (IVa3-e3), 3-(aryl)-4-methyl-3a,6-dihydropyrazolo[3,4-c]pyrazole-2(3H)-carbothioamide (IVa2-e2) and 4-(aryl)-3-methyl-1,3a,4,5-tetrahydropyrazolo[3,4-c]pyrazoles (IVa1-e1) were synthesized by conventional method where fused pyrazopyrazoles were prepared.  All the compounds were synthesized with good yield (56-81 %) and characterized by IR, 1H NMR spectral data and C, H, N elemental analysis. All the synthesized compounds exhibited analgesic and anti-inflammatory activities