General Papers ARKIVOC 2008 (xi) 112-122 ISSN 1551-7012 Page 112 © ARKAT USA, Inc. Synthetic and pharmacological studies on some 1-isonicotinoyl-3- methyl-4-(4-substituted phenyl)-3a,4-dihydro pyrazolo [3,4-c]pyrazoles and their ethoxyphthalimide derivatives Swati Ojha, Archita Bapna, and Ganpat L.Talesara * Synthetic Organic Chemistry Laboratory, Department of Chemistry, M. L. Sukhadia University, Udaipur (Raj.)- 313 001, India E-mail: gtalesara@yahoo.com Abstract Isoniazid reacted with ethylacetoacetate in absolute ethanol to give 2-isonicotinoyl-5-methyl-2,4- dihydro-3H-pyrazol-3-one (1), which upon condensation with various aldehydes (2a-d) afforded the related arylidene derivatives (3a-d). 1-Isonicotinoyl-3-methyl-4-(4-substitutedphenyl)-3a,4- dihydropyrazolo[3,4-c]pyrazoles (4a-d) were obtained as the result of cyclocondensation reaction between 3a-d and hydrazine hydrate. Subsequently compounds 4a-d were converted to corresponding 2-N-ethoxyphthalimido-6-isonicotinoyl-4-methyl-3-(4-substituted phenyl)-3,3a- dihydro pyrazolo[3,4-c]pyrazoles 6a-d by the treatment with phthalimidoxyethyl bromide (5). Structures of synthesized compounds were elucidated by means of IR, 1 H NMR and mass spectral data. Final compounds were screened for four biological activities namely “antibacterial, antifungal, antiviral and anticancer”. Keywords: Isoniazid, pyrazolo[3,4-c]pyrazoles, phthalimidoxyethyl bromide, antifungal, spectral data Introduction Isoniazid is reported as a well known and well acknowledged drug. 1-3 Isoniazid is one of the primary drugs used in combination with ethanbutol, rifampin, streptomycin and pyrazinamide to treat tuberculosis. 4 Despite the large number of compounds containing the isoniazid moiety which have already been synthesized and tested, there is still a need for new compounds of this kind, 5 due to the increasing resistance of bacterial strains of certain type of antibiotics. 6 The efficiency of pyrazole as chemotherapeutic agent is well established and their chemistry has been extensively studied. Pyrazole and its synthetic analogues have been found to exhibit industrial, agricultural and biological applications. 7-11 Pyrazoles are an interesting group of compounds many of which possess broad spectrum pharmacological properties, such as analgesic,