Some hitherto unknown novel bismesoionic compounds, 3-[4/3 (5H/substituted- 2-sulphido-1,3,4-thiadiazolium-4 carbonyl)phenyl]sydnones 5a?d and 6a-d and 4-[4 (5H/substituted-2-sulphido-1,3,4-thiadiazolium)benzoyl] (5H/substituted-1,3,4-thiadiazolium- 2-thiolates 9a?d have been synthesized from 3-[(hydrazinocarbonyl)phenyl] sydnones 1 and 2. A few of these compounds exhibited in vitro antitubercular activity and also antimicrobial activity higher than the employed reference drugs.

Schiff bases derived from 5-substituted salicylidine 3-[p-(5-substituted salicylidinehydrazinocarbonyl)]phenylsydnones and their transition metal complexes with Co(II), Ni(II), Cu(II), and Zn(II) have been synthesized and characterized by elemental analysis, molar conductance, magnetic susceptibilities, electronic, infrared, Proton Magnetic Resonance (PMR) ( 1 H NMR), Fast Atomic Bombardment-(FAB)-mass spectra, Electron Spin Resonance (ESR), and thermal studies. From the above spectral studies, it is concluded that the ligands viz., 3-[p-(salicylidinehydrazinocarbonyl)]phenylsydnone (L 1 ); p-(vanillidine hydrazinocarbonyl)]phenylsydnone (L 2 ); and 3-[p-(5 0 chlorosalicylicdinehydrazinecarbonyl)]-phenylsydnones (L 3 ) act as bidentate molecules coordinating through azomethine nitrogen and phenolic oxygen. The ligands and their metal complexes have been screened in vitro for antibacterial, antifungal, and antitumor activities. The results indicate that the biological activity has increased on complexation. The Cu(II) complexes of the above-said ligands have proven to be antitumor agents toward the P388/s tumor cells at lower concentrations.

The synthetic versatility of 3-[p-(hydrazinocarbonyl)]phenylsydnone is demonstrated in the syntheses of various heterocyclic compounds. For example, pyrazoles, fused pyranopyrazoles, 1,3,4-thiadiazoles, 1,3,4-oxadiazoles and 1,2,4-triazoles can be built on the phenyl ring of this 3-phenyl sydnone. The phenylsydnones prepared herein were characterized spectroscopically and subjected to antibacterial and antifungal screening. The compounds demonstrated high fungicidal activities. 3-[p-(hydrazinocarbonyl)]phenylsydnone has proven to be a versatile precursor for the synthesis of various related derivatives and may be used further in preparing various pharmaceutical and agricultural compounds.