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ABSTRACT:
A novel series of compounds containing coumarinyl moiety derivatives from 2-(2-oxo-4-phenyl-2H-chromen-7-yloxy)-acetohydrazide (2) were synthesized. The formed compounds have been evaluated by correct elemental analysis and spectral data (IR, MS, ^sup 1^H-NMR and ^sup 13^C-NMR). The antioxidant evaluation of some selected compounds indicated that tosyl hydrazide derivative 7 revealed promising antioxidant activity.
KEY WORDS: Coumarin acetohydrazide, Schiffs bases, oxadiazole, thiazolidinone, pyrazole, antioxidant activity.
INTRODUCTION:
Coumarin and its derivatives are a class of the most active heteroaromatic compounds that have drawn much attention due to their biological and pharmaceutical activities [1-9]. Many of these corn-pounds have proved to be active as anticancer [10], antifungal [11], antibacterial [12, 13], antitumor [14], anti-HIV [15], anti-inflammatory [16], anticoagulant [17] and antiviral activities including human immunodeficiency virus activities are well known [18],
On the other hand, a large number of hydrazides have been reported to be of biological interest [19, 20], while oxadiazole derivatives have been reported to possess antibacterial [21, 22], antifungal [23, 24] and other biological activities. Furthermore, a number of substituted pyrazoles were found to exhibit appreciable biological and chemotherapeutic activities [25-32], It was therefore thought worthwhile to incorporate the hydrazide, oxadiazole and pyrazole moieties into the coumarin nucleus.
RESULTS AND DISCUSSION
Chemistry
Applying the hydrazinolysis of ethyl 2-(2-oxo-4-phenyl-2H-chromen-7-yloxy) acetate (1) [33] with hydrazine hydrate in ethanol at refluxing temperature, 2-(2-oxo-4-phenyl-2H-chromen-7-yloxy) acetohydrazide (2) was obtained in good yield (Scheme 1).
On the other hand, refluxing 2 in formic acid for 5 hours affo-rded the N-formyl derivative 3 in high yield. Condensation of 3 with 4-aminobenzoic acid in acetonitrile as a medium containing a few drops of acetic acid gave 4-((2-(2-(2-oxo-4-phenyl-2H-chromen-7-yloxy)acetyl)hydrazinyl) methyleneamino)benzoic acid (4) as the sole product. Acetylation of hydrazide compound 2 by refluxing in acetic acid, afforded N'-acetyl-2-(2-oxo-4-phenyl-2H-chromen-7-yloxy) acetohydrazide (5). Also, condensation of hydrazide 2 with 4-nitrobenzoic acid in the presence of phosphorousoxychloride under reflux yielded 7-((5-(4-nitrophenyl)-l, 3, 4-oxadiazol-2-yl) methoxy)-4-phenyl-2H-chromen-2-one (6) in moderate yield, (Scheme 1).
Scheme 1
Treatment of acetohydrazide 2 with p-toluene sulfonyl chlo-ride in dry dioxane in the presence of a few drops of triethylamine (TEA) as a catalyst afforded 4-methyl-N'-(2-(2-oxo-4-phenyl-2H-chromen-7yloxy)acetyl)benzenesulfonohydrazide (7), while when 2 reacted with proper substituted benzoyl chlorides namely (4-chloro and 3,5-dinitrobenzoyl chloride) in refluxing dioxane in the prese-nce of pyridine yielded 4-chloro- N'-(2-(2-oxo-4-phenyl-2H-chrom-en-7-yloxy)acetyl)benzohydrazide (8a) and 3,5-dinitro-N'-(2-(2-oxo-4-phenyl-2H-chromen-7-yloxy)acetyl)benzohydrazide (8b), respe-ctively....