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Abstract
ABSTRACT
Certain novel N-acetyl-, N-phenyl- and N-thiocarbamoyl pyrazoles as well as 4,5-dihydroisoxazoles have been designed and synthesized, aiming to attain compounds with antiviral activity. In addition, new hybrid compounds such as pyrazol-1-yl thiazol-4(5H)-ones and pyrazol-1-yl thiazole derivatives have been prepared as potential nonnucleoside antiviral agents. Furthermore, one derivative of both thiazolidin-4-one as well as thiazol-3(2H)-amine were designed and synthesized with the aim to explore their antiviral activity. In order to obtain the target compounds, the following routes were adopted:
1. Condensation of acetophenone derivatives with 4-benzyloxy benzaldehyde in aqueous ethanolic solution of sodium hydroxide afforded the key intermediates α,β-Unsaturated ketones Ia-d.
2. Reacting the α,β-Unsaturated ketones Ia-d with hydrazine hydrate in acidic media (acetic acid) for 4 hours yielded the novel N-acetyl pyrazole derivatives IIa-d.
3. Cyclization of the chalcones Ia-d with phenyl hydrazine in ethanol in presence of sodium hydroxide led to the production of the novel N-phenyl pyrazoles IIIa-d.
4. Interaction of hydroxyl amine HCl with the corresponding key chalcones Ia-d afforded the title 4,5-dihydroisoxazole derivatives IVa-d.
5. Treatment of the α,β-Unsaturated ketones Ia-d with equimolar amounts of thiosemicarbazide in ethanolic solution of sodium hydroxide produced the novel N-thiocarbamoyl pyrazoles Va-d which in turn, were cyclized using either ethyl bromoacetate or phenacyl bromides through reflux in ethanol to afford the novel pyrazol-1-yl thiazol-4(5H)-ones VIa-d or pyrazol-1-yl thiazole VIIa-h, respectively.
6. Condensation of thiocarbohydrazide with 4-benzyloxy benzaldehyde in aqueous ethanol yielded the 1,5-Bis(4-(benzyloxy)benzylidene) thiocarbohydrazide VIII which was converted to thiazolidin-4-one IX and thiazol-3(2H)-amine X under the effect of ethyl bromoacetate and 4-bromo phenacyl bromide, respectively.
The purity of the newly synthesized compounds was checked by TLC, and the structures of these novel compounds were confirmed by elemental microanalyses and established by IR, 1HNMR, 13CNMR and mass spectrometry.
The present investigation necessitated the synthesis of the following key intermediates guided by the published literatures:
[1] 3-[4-(Benzyloxy)phenyl]-1-phenylprop-2-en-1-one (Ia).
[2] 3-[4-(Benzyloxy)phenyl]-1-(4-bromophenyl)prop-2-en-1-one (Ib).
[3] 3-[4-(Benzyloxy)phenyl]-1-(4-chlorophenyl)prop-2-en-1-one (Ic).
[4] 3-[4-(Benzyloxy)phenyl]-1-p-tolylprop-2-en-1-one (Id).
[5] 4-Bromo phenacyl bromide.
[6] 4-Chloro phenacyl bromide.
[7] 4-Methyl phenacyl bromide.
[8] Thiocarbohydrazide.
In the present study, the following new target compounds were prepared:
1) 1-Acetyl-5-[4-(benzyloxy)phenyl]-3-phenyl-4,5-dihydro-(1H)-pyrazole (IIa)
2) 1-Acetyl-5-[4-(benzyloxy)phenyl]-3-(4-bromophenyl)-4,5-dihydro-(1H)-pyrazole (IIb)