الفهرس 
Part oneOnly 14 pages are availabe for public view
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Abstract
Regarding the four research projects covered, they are: 1- A Novel One-Pot Synthesis of [l,2,4]Triazino[4,3-b][l,2,4,5] Tetrazines. 2- A New One-Pot Synthesis of pyrimido[l,2-b][l,2,4,5]Tetrazines. 3- Regioselectivity in Cyclization of Thiohydrazonate Esters and l5N-NMR Study of Azo-Hydrazone Tautomerism of 2-Arylhydrazono-3-oxo-1,4-benzothiazines. 4- Regioselectivity in the Reactions of Bis-hydrazonoyl halides with Pyrimidine-2-thiones. The first project: reactions of hydrazonoyl halides 6 with either 4-amino-2,3-dihydro-6-substituted-3-thioxo[l,2,4]triazin-5(4H)ones 1(2) or 4-amino-3-methylthio-6-substituted[l,2,4]triazin-5(4H)ones 3(4) in ethanol in the presence of triethylamine at reflux afforded the respective derivatives 9(10). The mechanism of formation of the latter was discussed and it was concluded that the products 9(10) are formed via the pathway A outlined in Scheme 1. The second project: reactions of hydrazonoyl halides 4a-i with either 3-amino-2,3-dihydro-6-methyl-2-thioxo-4(lH)-pyrimidinone 5 or 3-amino-6-methyl-2-methylthio-4(3H)-pyrimidinone 6 in ethanol in the presence of triethylamine or in pyridine at reflux were studied. They lead to the respective pyrimido[l,2-b][l,2,4,5]tetrazine derivatives 9 Scheme 2. Although the formation of the latter products from 7 and 10 can proceed via either pathway A and B outlined in Scheme 2, the latter route B was excluded on the following basis. First attempts to isolate either thiohydrozonates 10 or the thiohydrazide 11 failed under the reaction conditions employed. In addition, the formation of 9 from 7 or 8 seems to be in support of route A. The mechanism of the studied reactions was discussed and the structures of all new compounds were elucidated on the basis of their spectral (IR, MS, NMR) and elemental analyses. In the third project: reactions of thiophenol with series of ethyl arylhydrazonochloroacetate 1 and methyl phenylhydrazonochloroacetate 6 in ethanol in presence of triethylamine at room temperature were studied. The reaction products isolated prove to be the respective thiohydrazonate esters 3,7, respectively. When the latter were stirred in absolute ethanol saturated with hydrogen chloride gas they undergo to cyclization to give 2-arylhydrazone-3-oxo-l,4-benzothiazine 4, via elimination of ethanol and methanol, respectively. Also, it was found that the product 4 can be obtained directly by refluxing of 2-aminothiophenol with 1 or 6 in ethanol containing sodium ethoxide the structure of the product 4 was also confirmed by their alternative synthesis based on coupling of ethyl 2-oxo-benzo-l,4-thiazino-2-carboxylate 8 with diazotized anilines as in Scheme 3. In addition the tautomeric structure of product 4 were elucidated by the study there electronic spectra in solvents and 1H, 13C NMR and l5N NMR spectra. The resulted obtained indicate that the compound 4 in question exist predominately in the keto hydrazone 4A as shown in Scheme 3. In the fourth project :of this thesis research deals with elucidation of regioslectivity in the reaction of bis-hydrazoneyl halides with pyrimidine-2-thiones. Thus, the bis-hydrazonyl chloride 1 was found to react regioselectively with the pyimidine-2-thione 2, which have masked thiourea residue, to give the hitherto unknown annelated 2,3-bis(arylhydrazono)thiozoles 4 and 3,3’-bis (1,2,4-triazoles) 6 (Scheme 4). The substitution reaction products isolated from reaction of 1 with the thiones 2 can be assigned either one of the two alternative structures namely 7H-thiazolo[3,2-a]pyrimidin-5-one 4 or 5H-thiazolo[3,2-a]pyrimidin-7-one 5. Distinction between these two regioisomeric structures 4 and 5 was based on comparison of the spectral (IR and 13CNMR). Due to the poor solubility of the products 6a-c in most NMR occurred solvents, their 13C NMR spectra could not be recorded and their assigned structures were substantiated by their alternative synthesis. Thus, reaction of 1 with 2-methylthio derivatives 3 gave only 6 (Scheme 5). The assigned structures were also substantiated by the resulted of bonding energies calculations carried out by AMI program.