Synthesis and Biological Activity of Some Novel 4-( 5-Mercapto-1 , 3 , 4-thiadiazol-2-yl )-2-phenyl-5-[ 2-phenylvinyl ]-2 , 4-dihydro-3 H-1 , 2 , 4-triazol-3-one

A novel and efficient route have been designed for the synthesis of 4-(5-mercapto-1,3,4-thiadiazol-2-yl)-2-phenyl-5-[2-phenylvinyl]-2,4-dihydro3H-1,2,4-triazol-3-one. All the synthesized compound were characterized by elemental analysis, IR, H NMR, C NMR and mass spectra. All the synthesized products were evaluated for their antibacterial activity against B. Subtilis and E.Coli and antifungal activity against A. niger and C.Albican respectively. The results indicate that the present compounds may serve as better fungicides when compared to bactericides. The synthesized compounds have turned to be wonder by possessing antimicrobial properties.


Experimental
Melting points were determined in one end open capillary tubes on a Buchi 530 melting point apparatus and are uncorrected.Infrared (IR) spectra were recorded for the compounds on Perkin Elmer Spectrum RXI Spectrophotometer in KBr. 13 C nuclear magnetic resonance ( 13 C NMR) and 1 H nuclear magnetic resonance ( 1 H NMR) spectra were recorded for the compounds on Advance bruker (300 MHz) instrument.Chemical shifts are reported in parts per million (ppm) using tetramethylsilane (TMS) as an internal standard.All the new compounds have given CHN analysis within ±0.4% of the theoretical values.The purity of the compounds was confirmed by thin layer chromatography using silica gel glass plates and a solvent system of benzene:ethanol (8:2).The spots were developed in iodine chamber and visualized under ultra violet lamp.
All the chemicals purchased were of analytical reagent grade, and were used without further purification stated is confirmed by measuring M.P. Synthesis of 3-aryl sydnones, oxadiazolines and triazoles derivatives by slight modification in our reported literature methods 23 .

General procedure for compounds 2a-2h (Scheme 1)
To the 5-methyl-3-phenyl-1,3,4-oxadiazol-2(3H)-one (0.01 M) (1), 5-amino-1,3,4thiadiazole-2-thiol (0.01 M) in glacial acetic acid (GAA) was added and refluxed for 4 h.Obtained reaction mixture was poured into crushed ice and left overnight.The solid which separated out was filtered, washed thoroughly with cold distilled water, dried and recrystallised from hot ethanol.The other derivatives are also synthesized by same method.The yield, melting point and other physical properties of synthesized compound are recorded in Table 1.

General procedure for compounds 3a-3h (Scheme 1)
The title compounds were synthesized by following the procedure: Solution of 2 (0.01 M) and opportune benzaldehyde (0.01 M) were reacted with glacial acetic acid (10 mL) and refluxed for 12 h.The solid 4 which separated out was filtered with suction and recrystallised from dimethylformamide to give pure compound.The physical data of the compound 3 are given in Table 2.The IR spectra, 13 C NMR spectra and 1 H NMR spectra of the title compounds are as follows:

Biological activity
All the newly synthesized compounds were screened for their antimicrobial activity by cup plate method at 100 µg/mL concentration in DMF against the Bacterial strains viz., E. coli & B. subtilis and also against fungal strains viz., A niger and A. sereus.Norfloxacin for bacteria and griseofulvin as the reference drugs respectively.Some these compounds were less active against the bacterial strains, but some of them showed selective fungal inhibitory activity.The antimicrobial data of synthesized compounds are given in Table 3.

Table 2 .
Elemental Analysis of the compounds.

Table 3 .
Anti-microbial activities of compounds.