Behavior of 3-hydrazino-6-aryl-1,2,4-triazin-5-one as a strong nucleophile towards active electrophilic compounds and their antibacterial evaluation

The behavior of 3-hydrazino-6-aryl-1,2,4-triazin-5-one towards the active electrophilic compounds in polar and/ or non-polar solvents and various times and temperatures, has been studied. N-[2-(3-(3/5-(4Nitrophenyl)-5/3-thioxo-1H-1,2,4-triazol-1-yl)-5-oxo-1,2,4-triazin-6-yl)phenyl]pivalamides were obtained from the reaction of N-(2-(3-hydrazineyl-5-oxo-1,2,4-triazin-6-yl)phenyl)pivalamide with 4-nitrobenzoyl isothiocyanate in THF and/ or EtOH-piperidine respectively. Also, N-(2-(3-hydrazineyl-5-oxo-1,2,4-triazin-6yl)phenyl)pivalamide was shown a strong nucleophilic behavior by reaction with N-phenylthiourea to produce N-[2-(5-oxo-3-(2-(phenylcarbamothioyl)hydrazineyl)-1,2,4-triazin-6-yl)phenyl]pivalamide, which upon cyclization with diethyl carbonate produced N-(2-(5-oxo-3-(5-oxo-4-phenyl-3-thioxo-1,2,4-triazolidin-1-yl)1,2,4-triazin-6-yl)phenyl)pivalamide. Moreover, N-(2-(3-hydrazineyl-5-oxo-1,2,4-triazin-6-yl)phenyl)pivalamide studied its behavior by reaction with cyanoacetic acid, chloroacetonitrile, and/ or benzoyl carbonitrile to produce N-(2-(3-amino-4,8-dioxo-4H-[1,2,4]triazino[4,3-b][1,2,4]triazin-7-yl)phenyl)pivalamide,N-(2-(4-amino-8-oxo2H-[1,2,4]triazino[4,3-b][1,2,4]triazin-7-yl)phenyl)pivalamide and N-(2-(4-imino-8-oxo-3-phenyl-4H-[1,2,4] triazino [4,3-b][1,2,4]triazin-7-yl)phenyl)pivalamide. Structure of the products was established upon their elemental analysis and FT-IR, H/ C NMR, and MS. The new compounds were evaluated as antibacterial agents some Gram-positive and negative bacteria. Some compounds were showed the highest inhibition activity towards Pseudomonas aeruginosa, Bacillus subtilis, Bacillus cereus, and Sarcina lutea bacteria and lowest inhibitory activity against Escherichia coli bacteria.


Introduction
Polyfunctionalized 1,2,4-triazine has significant vital probes properties, as biological, pharmacological, and agriculture applications, as anti-HIV 1 , anticancer 2 , antimicrobial 3,4 , photochemical probes for the inhibition of vitiligo, 5 antibiotic resistances 6 . and anti-inflammatory 6 . On the other hand, phosphorusbearing 1,2,4-triazine mostly enhanced their physical, chemical, and biological properties. 7,8 Also, 3-hydrazino-6-aryl-1,2,4-triazin-5-one used to produce heterobicyclic as anti-HIV and/or molluscicidal activity against some snails. 7 As well as 3-thixio-1,2,4-traizin-5-one derivatives used as starting materials to obtain heteropolycyclic nitrogen systems as antioxidant and anti-inflammatory 9 . o-Diamines as hydrazino moiety are very active substrates for the building of various heterobicyclic nitrogen systems 9,10 . Abdel-Rahman et al. 11 , have been investigated the behavior of hydrazino-groups towards various bi-electrophilic compounds. Based on these observations, and as a part of our continuing work in these areas 12,13 , the present work describes other attempts for the behavior of 3-hydrazino-1,2,4triazinone towards some activated electrophilic compounds in different medium and conditions in view of their bactericidal effects.
The former structures of compounds 6 and 7 have been confirmed from that FT-IR spectra were showed ῡ at 1200-1180 cm -1 for C=S functional group, while that of compounds 8 and 9 recorded ῡ at 3200-3100 and 1640-1630 cm -1 for NH2 group. All compounds 8-10 showed a lacks CN group, which confirms the addition reactions have happened. 1 H NMR spectra of compounds 8 and 9 recorded at 3.5 ppm for NH2 protons while that of compound 10 showed at 5.5 ppm for =NH proton.
Finally, the synthesized compounds were exhibited antibacterial activity, thus, from the obtained results in Table 1 Table 2.
In comparison between the activity of compounds, we can be concluded that 3-thioxo-1,2,4-triazole moiety gave a high activity than 5-thioxo-1,2,4-triazole moiety, which may be the presence of cyclic NCSN part within the bio-conjugated systems.

Experimental
All chemicals were purchased from Merck and BDH and used without any further purifications. The melting points were recorded on Stuart scientific SMP30 (Bibby, UK) melting point apparatus and reported as uncorrected. A Perkin Elmer model RXI-FT-IR 55,529 cm -1 was used for recording the FT-IR spectra. A Brucker advance DPX 400 MHz using TMS as an internal standard was used for recording the 1 H and 13 C NMR spectra in deuterated DMSO (δ in ppm) as a solvent. AGC-MS-QP 1000 ex-model was used for recording the mass spectra. Elemental microanalysis was performed on a Perkin-Elmer CHN-2400 analyzer. All reactions were monitored by TLC, using silica gel coated Al plates with fluorescent indicator F254. 4-Nitrobenzoyl isothiocyanate was obtained from refluxing 4-nitrobenzoyl chloride with ammonium thiocyanate in dry acetone 11 , and 6-(2-aminophenyl)-3-thioxo-1,2,4-triazin-5(4H)one (1) also obtained from refluxing isatin with thiosemicarbazide in aq. NaOH 14 , according to the reported methods. Compound.   -3-thioxo-2,3,4,5-tetrahydro-1,2,4
The new compounds were dissolved in 5% DMSO to obtain a 0.5% stock solution. Grown cultures were used sterile nutrient agar medium in each Petri plate. The applied concentration in each 10, 30, and 50 mL of stock solution added. All the plates were incubated at 28°C for 24 h and the size of the resulted zone of inhibition determined.

Conflict of interest
The authors declare no conflicts of interest.