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https://ptsldigital.ukm.my/jspui/handle/123456789/519493| Title: | Synthesis, Reactions, Characterization And Antibacterial Studies Of Some Acyclic Ketene-N,S- And ��N,N-Acetals |
| Authors: | Wedad Melad Ali Al-Adiwish (P54733) |
| Supervisor: | Mohammad B. Kassim, Associate Prof. Dr. |
| Keywords: | Synthesis Studies Of Some Acyclic Ketene-N S- And ��N N-Acetals Reactions Studies Of Some Acyclic Ketene-N S- And ��N N-Acetals Characterization Studies Of Some Acyclic Ketene-N S- And ��N N-Acetals Antibacterial Studies Of Some Acyclic Ketene-N S- And ��N N-Acetals Organic compounds--Synthesis |
| Issue Date: | 25-Nov-2013 |
| Description: | Synthesis of α,α-dioxoketene-N,S- and -N,N-acetals has been a subject of great interest due to their wide applications. They are important and versatile reagents in organic synthesis especially for the preparation of heterocyclic compounds for the use in biological assays that may lead to the discovery of new drugs. Nucleophilic addition-elimination reaction of some secondary aliphatic N-methylalkyl and N-ethylalkyl amines as well as cyclic amines of pyrrolidine, piperidine and morpholine on known 3-[bis(methylthio)methylene]pentane-2,4-dione, ethyl-2-cyano-3,3-bis(methylthio) acrylate and 3-[bis(methylthio)methylene]malononitrile in toluene and ethanol at room temperature or under reflux in ethanol for some time intervals gave respective 13 new α,α-diacetylketene-N,S- and -N,N-acetals, seven new α-cyanoketene-N,S-acetals with three unexpected β-dialkylamine-α-cyano acrylates and three new α,α-dicyanoketene-N,N-acetals after purification by column chromatography. Some of these keteneacetals were used in the preparation of a series of pyrazoles, 5-aminopyrazoles and thiophenes. α-Cyano- and α,α-dicyanoketene-N,S-acetals were found to be more nucleophilic compared to α,α-diacetylketene-N,S-acetals. Cyclization occurred when α-cyanoketen-N,S-acetals and α,α-dicyanoketen-N,S-acetals were reacted with hydrazine hydrate under reflux in ethanol to afford eight new pyrazoles and three new 5-aminopyrazoles from good to excellent yields. On the other hand, treatment of ethyl 2-cyano-3,3-bis(methylthio)acrylate and 2-[methylthio(piperidin-1-yl)methylene]malononitrile with sodium sulfide under reflux in DMF, then chloroacetonitrile and finally potassium carbonate yielded tetra substituted thiophenes. The above 5-aminopyrazoles were utilized as intermediates for the synthesis of pyrazolo[1,5-a]-pyrimidines and pyrazolo[5,1-c][1,2,4]-triazines. They were reacted with 2-[bis(methylthio)methylene] malononitrile and two known α-cyanoketen-N,S-acetals under reflux in absolute ethanol in the presence of triethylamine to form seven new pyrazolo[1,5-a]-pyrimidines in low yields. They were also reacted with acetylacetone and acetoacetanilide under reflux in DMF in the presence of three drops of acetic acid to afford six new pyrazolo[1,5-a]-pyrimidines in good yields. On the other hand, diazotization of the three 5-aminopyrazoles with sodium nitrite, hydrochloric acid and acetic acid at 0-5 °C, followed by the reaction with active methylenes of acetylacetone and malononitrile in pyridine formed six new pyrazolo[5,1-c][1,2,4]-triazines from good to excellent yields. Furthermore, cyclocondensation of the above three 5-aminopyrazoles with 2,5-hexanedione in boiling glacial acetic acid produced three new 5-pyrrolylpyrazoles. Moreover, they were reacted with acetic anhydride within 15 minutes under mild condition to give three new 1-acetyl-1H-pyrazoles. All of the 64 new synthesized compounds were characterized by using elemental analysis and spectral data. Single crystal structure determination on 13 out of those 64 compounds has also been performed. Almost all of the synthesized compounds were evaluated for their antibacterial activity using the agar diffusion method. The tested organisms were Gram-positive Staphylcoccus aureus and Bacillus subtilis, and Gram-negative Escherichia coli and Klebsiella pneumoniae.. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of some selected compounds were also determined.,PhD |
| Pages: | 308 |
| Call Number: | QD262 .A434 2013 |
| Publisher: | UKM, Bangi |
| Appears in Collections: | Faculty of Science and Technology / Fakulti Sains dan Teknologi |
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