Various Routes to Synthesise 3-Thioxo-1 , 2 , 4-Triazine-5-One Derivatives as Antimicrobial Agents

A simple condensation afforded some new 3-thioxo-1,2,4-triazin-5-one derivatives (4, 6 and 8). Utilizing a facile condensation of (E)-4-(4’-bromo styryl)-2-oxo-3-buteneoic acid with thiosemicarbazide, dithioic formic acid hydrazide, and thiocarbahydrazide in different conditions. Structures of these compounds were confirmed by elemental and spectral analysis. The preliminary biocidal activity of these products were evaluated against some microbial and compared to Mycostatine and piperacillin as antibiotics were most of derivatives exhibited good activity.

Also dithioic formic hydrazide (2) synthesized by addition of CS 2 to hydrazine hydrate in dioxan at room temperature with continuous stirring (m.p 130˚C) [18].Thiocarbohydrazide produced from reflux CS 2 with hydrazine hydrate in aqueous ethanol (m.p 170˚C) [19].6) (Scheme 1).Formation of 6 might be take place via a nucleophilic attack of amino-group of sulfa to SH of compound 5 followed by heterocyclisation (Scheme 2).
A higher stability of compound 8 as Sencore analogues, may be due to a various tautomeric and H-bonding via internal effects (Figure 3).

The Antimicrobial Evaluation
The newly prepared compounds 3 -8 have been evaluated as antimicrobial agents against Gram-negative and Gram-positive bacteria as Escherichia Coli, Klebsiella pneumoniae, Pseudomonas aeruginosa and Staphylococcus Aureus,  were recovered on Nutrient agar and MacConkey agar.Two fungi, Candida albicans and Aspergillus fumigatus were isolated on Sabouraud Dextrose Agar (Oxide).The in vitro tested use agar diffusion disk method [20].DMSO used as solvent and the antimicrobial potentialities of the tested compounds were estimated by placing pastoralized filter paper disks (11 mm diameter) impregnated with 50 mg/disk, and showed inhibition zones (IZ) measured after 24 -28 h incubation at 37˚C for bacteria and after 5 days incubation at 28˚C for fungi.References antibiotic disks (11 mm in diameter) supplied by (BBL), piperacillin (PIP) and fungicide Mycostatine were used for comparison [21].The results obtained outline in Table 1.
From the results obtained in Table 1.We can conclude that: Generally, the

Experimental
The

Conclusion
Various routes to synthetic polyfunctional 1,2,4-triazine derivatives have been used (E)4-aryl-2-oxo-3-buteneoic acid (1), dithioic formic acid hydrazide, thiosemicarbazide and thiocarbohydrazide in different media.Most of these targets exhibit a very good antibacterial and antifungal activity in compared with the reference antibiotics used.

compounds 4 ,
6 and 8 exhibit a growth inhibition activity more than open derivatives.The compound numbered 8 recorded the highest inhibition activity more than other compounds including the standard antibiotic used.The Structure Activity Relationship (SAR) showed that presence of a sulfonamide, mercapto and amino groups led to enhance the activity.Minimum inhibitory concentration (MIC) for the active synthesised compounds as 4, 6 and 8 displayed a very good antimicrobial activity in compared with the standard antibiotic used.
melting point recorded on Stuart scientific SMP3 (Bibby, UK) melting point apparatus and reported as uncorrected.A Perkin Elmer (Lambda EZ-2101) double beam spectrophotometer (190 -1100 nm) used for recording the electronic spectra.A Perkin Elmer model RXI-FT-IR 55,529 cm −1 used for recording the IR spectra.A Brucker advance DPX 400 MHz using TMS as an internal standard for recording the 1 H NMR 13 C nmr spectra in deuterated DMSO (δ in ppm).AGC-MS-QP 1000 Ex model used for recording the mass spectra.Elemental analysis performed on Micro Analytical Center of National Reaches Center-Dokki, Cairo, Egypt.

Table 1 .
The Antimicrobial evaluation of the new compounds 3 -8.