In scheme (), the starting ester (1)  was synthesized by heating a mixture of acetoacetamide, ethyl cyanoacetate and sulfur in the presence of morpholine. Heating the ester 1 with hydrazine hydrate in ethanol gave rise to the hydrazide 2. Condensation of the hydrazide 2 with acetyl acetone or benzoylacetone in ethanol containing glacial acetic acid afforded the corresponding 3,5-dimethylpyrazole 3a and 3-methyl-5-phenylpyrazole 3b. The pyrazole derivative 4 was prepared by heating the acid hydrazide 2 with ethyl pyruvate in ethanol containing glacial acetic acid. The 3,5-dioxopyrazolidine derivative 5 was successfully achieved by heating 2 with diethylmalonate. On the other hand, refluxing of 2 with ethyl acetoacetate in ethanol containing glacial acetic acid gave the required 5-oxo-4,5-dihydro-1-pyrazole derivative 6. The chemical structure of compounds 3a, b, 4, 5 and 6 were verified by analytical and spectral data.
Three series of pyrazole, thiazole and 1,3,4-oxadiazole, derivatives were synthesized starting from 5-amino-4-(hydrazinocarbonyl)-3-methylthiophene-2-carboxamide (2).
In the present study, twenty new 5-amino-4-substituted-3-methylthiophene-2-carboxamide derivatives were prepared and their chemical structures were confirmed by spectral analyses in addition to elemental analyses. All compounds were investigated for their preliminary effect on the replication of hepatitis-C virus (HCV) in HepG2 hepatocellular carcinoma cell line infected with the virus using the reverse transcription polymerase chain reaction technique. All compounds were found to inhibit the replication of HCV RNA (–) strands at the EC99, meanwhile, eight compounds (3a, 6, 7a, 7b, 9a, 9b, 10a and 11b) were proved to inhibit replication of both (+) and (–) strands at very low concentration range (EC99 = 0.08- 0.36 µg/mL).
The synthesis of the pyrimidine, pyrazole, triazolopyrimidine and imidazopyrimidine derivatives 4–7 were carried out by reacting commercially available benzoylacetone 1, dimethylformamide dimethylacetal (DMF-DMA), 4-amino-1,2,4-triazole and 2-aminobenzimidazole. Previously 1,1′-(3-methyl-4-phenylthieno[2,3-b]thiophene-2,5-diyl)diethanone 2 was synthesized starting from benzoylacetone 1. The method consists of sequential directed nucleophilic addition, side chain deprotonation, nucleophilic addition, and cyclization using a nitrogen or sulfur moiety as internal nucleophile. Condensation of 2 with dimethylformamide dimethyl acetal (DMF-DMA) under reflux for ten hours in the presence of xylene furnished enaminone 3. Reaction of enaminone 3 with N-nucleophiles, such as urea derivatives in dioxane or EtOH/DMF mixture under reflux for four to six hours in the presence of a catalytic amount of ZnCl2 as a Lewis acid afforded 4a–c. The formation of compounds 4a–c would involve an initial addition of the amino group in urea to the activated double bond in enaminone derivative 3, followed by deamination to an intermediate, which then undergoes cyclization and aromatization via loss of water, affording the final isolable product. Similarly, enaminone derivative 3 cyclized with hydrazine compounds by refluxing with absolute ethanol for six hours. The novel bispyrazole 5a was assumed to be formed via addition of the amino group in the hydrazine to the activated double bond of the enamine derivative, followed by deamination, dehydration, and subsequently nucleophilic cyclization to afford the final product. The utility of enaminone 3 in the synthesis of annelated heterocycles was further explored via its reaction with 4-amino-1,2,4-triazole in absolute ethanol under reflux for seven hours in the presence of a catalytic amount of ZnCl2 affording compound 6. The study was extended to investigate the behavior of enaminone derivatives 3 with different nucleophiles such as 2-aminobenzimidazole in order to synthesize various heterocyclic ring systems. Thus, the reaction of 3 with 2-iminobenzimidazole in refluxing ethanol in the presence of catalytic amount of ZnCl2 furnished the corresponding product 7. The structures of these compounds were determined by 1H-NMR, EI, IR and UV spectroscopic, and micro analyses for carbon, hydrogen and nitrogen .
RESULT AND DISCUSSION: In present study new 3-(2'-hydroxy-3'-nitro-5'-methylphenyl)-5-(aryl/heteryl) pyrazoles have been synthesized by the reaction of 1-(2'-hydroxy-3'-nitro-5'-methylphenyl)-3-aryl/heteryl-2-propen-ones i.e. chalcone by reaction with hydrazine hydrate in ethanol. Structures of all these synthesized compounds were established on the basis of spectral data (IR, NMR) and elemental analysis. All the compounds (IIa-IIj) were tested for their antimicrobial activity against the bacteria Escherichia coli, Staphylococcus aureus,
Antibacterial activity of synthesized compounds (IIa-IIj): For antibacterial test sample solution of all synthesized 3-(2' – hydroxyl - 3' - nitro-5'-methylphenyl)-5-(aryl/heteryl) pyrazoles was prepared by dissolving 100mg of sample in 1ml of DMF. All the synthesized compounds (IIa-IIj) were tested by disc diffusion method 9 against the bacteria as Escherichia coli, Staphylococcus aureus, Salmonella typhi, Pseudomonas aeruginosa, and Proteus vulgaris.
ABSTRACT: Heterocyclic compounds are well known for their different biological activities like anti-inflammatory, antibacterial, antifungal, anticancer, insecticidal, pecticidal, antibiotic, etc. the versatile applications of oxygen, nitrogen and sulphur containing heterocyclic compounds have made this area of extensive research. The present study deals with the synthesis of some new 3-(2'-hydroxy-3'-nitro-5'-methylphenyl)-5-(aryl/heteryl) pyrazoles synthesis from 1-(2'-hydroxy-3'-nitro-5'-methylphenyl) – 3 - aryl/heteryl - 2-propen-ones i.e. chalcone by reaction with hydrazine hydrate in ethanol and synthesized compounds screening for antimicrobial activity
INTRODUCTION: Heterocyclic compounds are well known for their different biological activities. The versatile applications of oxygen, nitrogen and sulphur containing heterocyclic compounds have made this area of extensive research. Pyrazoles have been studied because of their wide range biological and pharmacological activities. These compounds have been found to be effective as antimicrobial, antiinflamatoryl 1, herebicidals 2, antibacterial 3 etc. The diverse properties of pyrazoles have promoted to synthesis some new pyrazoles. The synthesized3-(2'-hydroxy-3'-nitro-5'-methylphenyl)-5-(aryl/heteryl) pyrazoles were screened for their antimicrobial activity against bacteria like Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa,