الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 316 |  |  |
| | | from | 316 | | |
Abstract
SUMMARY
This work illustrates the versatile role of tetrahydropyrimidine moiety in the synthesis of different heterocyclic systems from readily obtainable materials.
The work has been divided into three main parts:-
i- First part deals with tetrahydropyrimidine derivative.
ii- Second part deals with β-enaminonitrile.
iii- Third part deals with chemical behaviour of hydrazinopyrimidine moiety towards different electrophiles.
First part: Synthesis and reactions of tetrahydro-pyrimidine derivative.
Tetrahydropyrimidine derivative 1 was prepared via condensation of thiourea with arylidene ethyl cyanoacetate in refluxing ethanol. Some fused heterocyclic systems namely, thiazolo[3,2-a]pyrimidine derivatives 2 and 3 have been isolated via treatment of tetrahydropyrimidine 1 with bromomalononitrile and/or chloroacetamide respectively.
Condensation of compound 3 with substituted aromatic aldehydes namely, 4-chlorobenzaldehyde and / or 4-methoxybenzaldehyde afforded the corresponding benzylidene derivatives 4a,b.
Chlorination of tetrahydropyrimidine 1 with a mixture of phosphorus pentachloride and phosphorus oxychloride as a chlorinating reagent gave the chloropyrimidine derivative 5 which has been allowed to react with glycine, sodium azide and / or anthranilic acid to afford dihydropyrimidine 6, tetrazolopyrimidine 7 and pyrimidoquinazolinone 8 respectively.
Alkylation of tetrahydropyrimidine 1 with ethyl iodide in the presence of sodium ethoxide furnished S-alkylated product 9 which has been chlorinated to afford the chlorinated product 10. Pyrimidine derivative 10 underwent thiation under the effect of thiourea to give thioxodihydropyrimidine 11. Alkaline hydrolysis of tetrahydropyrimidine 1 using 10% alcoholic sodium hydroxide solution gave dioxotetrahydropyrimidine derivative 12 [cf. scheme I].
Second part: Reactions of β-enaminonitrile.
Enaminonitrile 2 is the key starting material for design and synthesis of fused novel heterocyclic systems. Thus, when enaminonitrile 2 was allowed to react with formamide, formic acid and / or sodium nitrite, it afforded pyrimidothiazolopyrimidine derivatives 13 & 14 and pyrimidothiazolotriazine 15 respectively.
On the other hand, treatment of enaminonitrile 2 with ethyl chloroacetate, carbon disulfide, neat triethyl orthoformate and /or diethyl malonate furnished thiazolopyrimidine 16, 17, pyrrolothiazolopyrimidine 19 and/ or thiazolo-pyrimidine derivative 20 respectively [cf. scheme II].
Third part: chemical behaviour of hydrazinopyrimidine moiety towards different electrophiles.
Hydrazinolysis of tetrahydropyrimidine 1 afforded sulfur free compound which was identified as hydrazinopyrimidine 21. Diacetylhydrazinopyrimidinyl acetate 22 and Schiff bases 23a-c have been obtained via reaction with freshly distilled acetic anhydride and / or substituted aromatic aldehydes with hydrazinopyrimidine derivative 21.
Treatment of hydrazinopyrimidine derivative 21 with thioglycolic acid, acetylacetone, formic acid, benzoyl chloride and / or formamide afforded dihydropyrimidine 24, pyrazole 25 and / or triazolopyrimidine derivatives 26-28 respectively.
Pyrazole derivative 29 and dioxopyrazolidine 30 were obtained via reaction of hydrazinopyrimidine derivative 2 with ethyl cyanoacetate and / or diethyl malonate respectively [cf. Scheme III].
Biological Activity
Antioxidant Evaluation
1- Determination of Total Antioxidant Capacity (TAC)
The antioxidant activities of the synthesized compounds were evaluated via phosphomolybdenum antioxidant assay. Moreover, the results showed that hydrazinopyrimidine 21 and Schiff bases 23a-c have the most potent levels of activity. Additionally, compounds 1, 6, 9, 22, 27-30 were found to be moderate active.
2- Reducing Power Antioxidant Assay (RPAA)
The reducing power of the tested compounds can be used as a significant indicator of its potential antioxidant activity. Furthermore, absorbance increasing (OD values) indicated the increasing in reducing power of the samples.
3- Conclusion
On the basis of the results obtained in this study, it is concluded that all synthesized compounds exhibit high reducing power capabilities.
Scheme I
Scheme II
Scheme III