Synthesis of New Fluorinated 1 , 2 , 4-Triazino [ 3 , 4-b ] [ 1 , 3 , 4 ] thiadiazolones as Antiviral Probes-Part II-Reactivities of Fluorinated 3-Aminophenyl-1 , 2 , 4-triazinothiadiazolone

Some new fluorinated 3-N-acyl/3-N-alkylaminophenyl-1,2,4-triazino[3,4-b][1,3,4]thiadiazolones (2-12) have been obtained from treatment of 2-(4'-fluorophenyl)-6-(2'-amino-5'-fluorophenyl)1,2,4-triazino[3,4-b][1,3,4]thiadiazol-4-one(1) with active functional oxygen, sulfur and halogen compounds in different conditions. Former structures of the products have been characterized from elemental and spectral data (UV, IR, NMR and Mass). The new products were evaluated as potential anthelmintic drugs.


Introduction
The treatment of infectious diseases still remains an important and challenging problem because of a combination of many factors including emerging infectious diseases and the increasing number of multi-drug resistant microbial pathogens [1]- [4].There is real perceived need for the discovery of new compounds endowed with biocidal activity.Through the various molecules designed and synthesized for this aim, it was demonstrated that fluorinated 1,2,4-triazine fused with 1,3,4-thiadiazole systems.The introduction of fluorine atom to the heterocyclic systems improves or enhances the medicinal properties [5]- [9].On the other hand, most of heterocyclic nitrogen systems bearing an amino-groups exhibit a wide spectrum of biological activities [10].And their use is as starting material.
Abdel-Rahman et al. [16], reported that 1,2,4-triazino [3,4-b][1,3,4]thiadiazolones (Figure 1) used as anti HIV and anticancer drugs.In contamination of our work in these researches for new biocidal agents [17], the present investigation reports the preparation of fluorinated 3-substitutedamino-1,2,4-triazino [3,4-b] [1,3,4]thiadiazolones starting from the corresponding 3-amino analogus, as potential anthelmintic drugs.Bonded phosphorus atoms with S, O, N and C-atoms of heterocyclic system enhance their biocidal properties as herbicides, pesticides, insecticides and molluscicidal agents [20]- [22].With this observations, the present work aims to synthesize of new fused heterobicyclicbearing fluorine and phosphorus atoms through phosphorylation of compound 1 with diphenyl phosphoryl chloride in warm DMF to give 3-(2'-diphenylphosphatoamino- Due to a higher nucleophilicity of amino-group and the better displacement of labile chlorine atom of halo acids the interested point in this investigation is a simple nucleophilic attack of amino-group of compound 1 to a higher electrophilic carbons of α-haloacids as monochloroacetic acid and/or 1,1-dichloroacetic acid in warm DMF, yielded [23]  The adducts formed by reactions of nitrogen containing aromatic heterocycles with various electrophilic carbon, may be stable systems, or they can undergo further transformation, such as aromatization.

Results and Discussion
Abdel-Rahmanetal reported [1] [25], fluorine substituted thiobarbituric acid derivatives use as anti HIV-1 and cyclin dependent kinase 2 (CDK2) for cell tumor division, thus ring closure reaction of compound 3 with malonic acid in boiling with glacial acetic acid afforded the fluorine substituted N,N'-disubstitutedthiobarbituric acid 13 (Scheme 7).Formation of compound 13 was deduced from ring closure reaction of substituted thiourea 3 with malonic acid (Figure 2).13 Former structures of the fluorinated 1,2,4-triazino [3,4-b][1,3,4]thiadiazolonederivatives have been established by help of their correct elemental analysis and spectral measurements: 1) UV absorption spectra of most N-acyl/phosphoryl derivatives for example 4, 6 and 7 recorded λ max 304 nm as parent amino-derivatives 1, which is may be that electronic inhibition over NH 2 by high electronic acceptor acyl, and/or phosphoryl.On the other hand, UV absorption spectra of compound 5 and 8 showed λ max at 311, and 375 nm respectively, which is may be the introduction of COCF 3 and/or COC 6 H 4 F-p to an amino group of 1. Thus NH proton of these compounds is highly acidic character.In addition, UV absorption spectrum of 13 showed an additive λ max at 410 nm, which attribute to formation of fluorinated thiobarbituric acid bearing of 1,2,4-triazino-1,3,4-thiadiazinone moiety.2) IR-spectra of all the obtained compounds (expected 6, 10, and13) recorded the absorption bands at 3200 -3100 cm for NH functional group, while, that of compounds showed an two C=O of NH acyl and 1,2,4-triazinone at 1690 -1650 cm −1 .All the synthesized showed a charactic bands of stretching and bending of C-F at γ 1250 and 720 cm −1 .Only the compounds 7, exhibited the presence of P=O and C-O-Ar at 1097 and 1016 cm −1 , while the compounds 4, 9, 11, and 12 showed the absorption bands of aliphatic groups at 2880 and 1440 cm −1 .Some compounds as 5, 7, 8, and 11recorded a lack's of NH functional group, which is may be formation a type of H-bonding (Figure 3). 3) NMR spectra of the new synthesized compounds was confired that structures.a) 1    .Also present M +2 is attributed to S and F isotopic (Figure 4).On the other hand, mass fragmentation study of compound 7 recorded a molecular ion peak at m/e 590 with a base peak at m/e 248 as C 12 H 11 NPO 3 iminophosphato ion radical with 4-fluorophenyl cation at 95%.Stability of a base peak is may be due to a higher stability of N = P group, which supported by donation and back-donation between N and P atoms (Figure 5).

Experimental
Melting points of the products were determined on Stuart SMP 3 (UK) and uncorrected.UV absorption spectra (λ max nm) were recorded in DMF on Shimadzu UV and visable 310 IPC-spectro-photometer.A Perkins Elmer Model RXI-FT IR system 55529 used for recording IR spectra of the prepared compounds γ cm −1 .A Brucker advanced D P X 400 MHz model using TMS as internal standard used for recording the 1 H and 13 C NMR spectra of the compounds on deuterated (CDCl 3 , d 6 , δ ppm).Mass spectrum was measured on GCMS Q 1000 Ex at 70 eV.Elemental microanalysis were performed by the microanalytical at Cairo-University, Egypt.A mixture of compound

Pharmacological Evaluation
1,2,4-Triazine derivatives showed a wide biocidal spectrum [13]- [15].Also, 1,3,4-thiadiazoles exhibited a large biocidal agents [11] [12].In addition, introduction of both fluorine atoms and/or amino groups to heterocyclic systems often improve their medicinal properties [5]- [9].Thus, in search for new drugs as potential anthelmintic to control on the smoke diseases, the present work, aim to obtain new drugs.All the new synthesized compounds were screened for their anthelmintic activity against H. nana infection in mice, by using the standard method of steward.The oral dose was 200 mg/Kg given for 2 days.Only the compounds 1, 3, 5, 6, 7, 9 and 13 recorded a weak activity (10 <%).On the other hand, evaluation of these compounds against N-brasiliensis infection in rats ta the same oral dose, by using other standard method [26] [27].The obtained results showed that the activity in range of 25% -60% (Table 1).
From the obtained results (Table 1) we can be conclude that compounds containing COCF 3 are highly effect than aromatic C-F.also, presence of phosphate group bonded to NH enhance that activity.Full fluorinated N,N'-diarylthiourea showed a rise activity towards N-brasifiensis.As well as N-alkyl systems exhibited a moderate activity.Thus, atype of both compounds 5 and 7 would present a fruitful matrix for the future development of a new class of potential anthelmintic agents, that deserves further investigation and derivation.A simple of nucleophilic attack of amino group of fluorinated 1,2,4-triazino[2,3-c]thiadiazolone to various electrophilic agents was deduced to give N-substituted analogues.The anthelmintic activity of these systems was evaluated.Among these tested analogs, compounds 5 and 7 showed 50% -60% activity, while all the tested compounds exhibited below 10% activity towards H. nana.

Table 1 .
Anthelmintic activity of the new synthesized compounds.