Abstract
A series of 3,5-disubstituted pyrazole-1-carboxamides were obtained by treatment of chalcones with semicarbazide hydrochloride in dioxane containing sodium acetate/acetic acid as a buffer solution. N-acetyl derivatives of pyrazole-1-carboxamides were isolated in good yields either by treatment of the carboxamide derivatives with acetic anhydride or refluxing chalcones with semicarbazide in ethanol containing few drops of acetic acid to give the corresponding hydrazones. Subsequent treatment of hydrazones with acetic anhydride gave the desired N-acetyl pyrazole-1-carboxamides derivatives. When chalcones were refluxed with dioxane containing few drops of acetic acid, 4,5-dihydropyrazole-1-carboxamides were isolated, which were subsequently oxidized using 5% sodium hypochlorite in dioxane to afford pyrazole-1-carboxamides. The structures of isolated compounds were confirmed by elemental analyses and spectral methods. The isolated compounds were tested for their antimicrobial activities.
Highlights
In view of this and our continued interest in the synthesis of pyrazoles [1,2,18,19], it was thought of interest to synthesize some new pyrazole derivatives starting from chalcone and semicarbazide [16,20]
In this paper we show that reaction of chalcones 1a-f with semicarbazide under different reaction conditions can affect the type of the product obtained and reaction pathways
The in vitro antimicrobial activities of the newly synthesized compounds 3-5 were assayed against four test organisms (Staphylococcus aureus ATCC6538P, Escherichia coli ATCC8739, Pseudomonas aeruginosa ATCC9027 and Candida albicans ATCC2091) following the agar well-diffusion method [29] and using rifampicin (5 μg/disc) and ampicillin (10 μg/disc) as standard drugs
Summary
Pyrazoles are an important class of five-membered heterocyclic compounds and were found to have potential antimicrobial [1,2,3], anti-inflammatory [4], antipyretic [5], antidepressant [6,7], tranquillizing [8], anticancer [9,10], antiviral [11], antihypertensive [12], antiarrhythmic [13], Molecules 2011, 16 antitubercular [14], psychoanaleptic [15], anticonvulsant [16] and antidiabetic [17] activities. In view of this and our continued interest in the synthesis of pyrazoles [1,2,18,19], it was thought of interest to synthesize some new pyrazole derivatives starting from chalcone and semicarbazide [16,20]
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