Hakan Bektas

Synthesis and antimicrobial activities of some new 1,2,3-triazole derivatives.

Some novel 4,5-disubstituted-2,4-dihydro-3H-1,2,4-triazol-3-one (3, 6, 8, 9) derivatives and or 3-(4-methylphenyl)[1,2,4]triazolo[3,4-b][1,3]benzoxazole (5) were synthesized from the reaction of various ester ethoxycarbonylhydrazones (1a-e) with several primary amines. The synthesis of 4-amino-5-(4-chlorophenyl)-2-[(5-mercapto-1,3,4-oxadiazol-2-yl)methyl]-2,4-dihydro-3H-1,2,4-triazol-3-one (13) was performed starting from 4-Amino-5-(4-chlorophenyl)-2,4-dihydro-3H-1,2,4-triazol-3-one (2) by four steps; then 13 was converted to the corresponding Schiff base (14) by using 4-methoxybenzaldehyde. Finally, two Mannich base derivatives of 14 were obtained by using morpholine or methyl piperazine as amine component. All newly synthesized compounds were screened for their antimicrobial activities and some of which were found to possess good or moderate activities against the test microorganisms.

Synthesis of new bis-1,2,4-triazole derivatives.

A series of new 1,2/1,3-bis[o-(N-methylidenamino-3-aryl-5-phenyl-4H-1,2,4-triazole-4-yl)phenoxy]ethane/propane derivatives 4 were prepared in good yields by treatment of 4-amino-3-aryl-5-phenyl-4H-1,2,4-triazoles 2 with certain bis-aldehydes 1.Compounds 4 were reduced with NaBH(4) to afford the corresponding 1,2/1,3-bis[o-(N-methylamino-3-aryl-5-phenyl-4H-1,2,4-triazole-4-yl)phenoxy]ethane/propane derivatives 5. All new compounds were characterized by IR, (1)H-NMR, (13)C-NMR and mass spectral data.

Synthesis of Schiff and Mannich Bases of Isatin Derivatives with 4-Amino-4,5-Dihydro-1H-1,2,4-Triazole-5-Ones

Ethyl imidate hydrochlorides 1 were prepared by passing HCl gas through solutions of substituted benzyl cyanides and absolute ethanol. Ethoxycarbonylhydrazones 2 were synthesized from the reaction of compounds 1 with ethyl carbazate. Treatment of 2 with hydrazine hydrate leads to the formation of substituted 4-amino-4,5-dihydro-1H-1,2,4-triazole-5-ones 3. Isatin and 5-chloroisatin were added to 3 to form Schiff bases 4 and N-Mannich bases 5 of these compounds were synthesized by reacting with formaldehyde and piperidine. Their chemical structures were confirmed by means of IR, 1H- and 13C-NMR data and by elemental analysis.

Microwave-assisted synthesis of new benzimidazole derivatives with lipase inhibition activity

Abstract A practical protocol has been used for the synthesis of benzimidazoles. The reaction of iminoester hydrochlorides of phenylacetic with 4,5-dichloro-1,2-phenylenediamine under microwave irradiation leads to the benzimidazole derivatives with good yields and in short reaction times. After the synthesis of benzimidazoles, we synthesized ester and hydrazide derivatives under microwave irradiation with good yields. All compounds were evaluated with regard to pancreatic lipase activity and 3b, 3c, 5a and 6a showed lipase inhibition at various concentrations.

Synthesis of eperezolid-like molecules and evaluation of their antimicrobial activities

Abstract3-Fluoro-4-(4-phenylpiperazin-l-yl)aniline (II) prepared from 3,4-difluoro nitrobenzene was converted to the corresponding Schiff bases (III) and (IV) by treatment with 4-methoxybenzaldehyde and indol-3-carbaldehyde, respectively. Treatment of amine (II) with 4-fluorophenyl isothiocyanate afforded the corresponding thiourea derivative (V). Compound (V) was converted to thiazolidinone and thiazoline derivatives (VI) and (VII) by cyclocondensation with ethylbromoacetate or 4-chlorophenacylbromide, respectively. The synthesis of carbothioamide derivative (X) was performed starting from compound (II) by three steps. Treatment of compound (X) with sodium hydroxide, sulfuric acid, or chlorophenacyl bromide generated the corresponding 1,2,4-triazole (XI), 1,3,4-thiadiazole (XII), and 1,3-thiazolidinone (XIII) derivatives, respectively. The structural assignments of new compounds were based on their elemental analysis and spectral (IR, 1H-NMR, 13C-NMR, and LC-MS) data. In the antimicrobial activity study all the compounds revealed high anti-Mycobacterium smegmatis activity.

Cadmium and nickel determinations in some food and water samples by the combination of carrier element-free coprecipitation and flame atomic absorption spectrometry

A procedure for separation and enrichment of Cd(II) and Ni(II) ions based upon carrier element-free coprecipitation by using an organic coprecipitant, 2-{4-[2-(1H-Indol-3-yl)ethyl]-3-(4-methylbenzyl)-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl}-N′-(3-fluoro-phenylmethyliden) acetohydrazide, prior to their flame atomic absorption spectrometric detections has been developed. The effects of varied experimental conditions on the performance of the developed method such as pH, sample volume, amount of coprecipitating agent, etc. were evaluated in detail on the recovery of analyte ions, and the influences of some anions and cations were investigated. The limits of detection for Cd(II) and Ni(II) ions based on three times the standard deviation of the blanks (N: 10) were obtained as 0.70 μg L−1 and 1.21 μg L−1, respectively. The accuracy of the method was tested by analyzing a certified reference material and by spike tests. The method was applied to determine the levels of cadmium and nickel in stream and sea water, rice, red lentil, and wheat samples.

Syntheses and biological activities of new hybrid molecules containing different heterocyclic moieties.

4‐Aryl‐5‐(pyridin‐3‐yl)‐4H‐1,2,4‐triazole‐3‐(thi)oles 5–7, obtained starting from nicotinic acid hydrazide were converted to the corresponding Mannich bases 12–24 by the reaction with several heterocyclic amines in the presence of formaldehyde. The synthesis of S‐alkylated compounds 8–11 was performed from the reaction of the corresponding triazol‐5‐thioles with various alkyl halides. The condensation of carbo(thio)amides 2–4 with 4‐chlorophenacyl bromide afforded the corresponding 1,3‐thia(oxa)zol‐2(3H)‐ylidene]pyridine‐3‐carbohydrazides 25–27. 1,3‐Thia(oxa)zolidine derivatives 28–30 were obtained from the cyclization reaction between compounds 2–4 and ethyl bromoacetate. All newly synthesized compounds were screened for their antimicrobial, antiurease, and antilipase activities. The biological activity studies revealed that all the compounds screened showed good or moderate antimicrobial, antiurease, and/or antilipase activity.

Synthesis and Antioxidant Properties of Some New 3-(4-Chlorophenyl)-5- (pyridin-4-yl)-4H-1,2,4-triazole Derivatives

A series of new 3-(4-chlorophenyl)-5-(pyridin-4-yl)-4-(arylmethyleneamino)-4H-1,2,4-triazole derivatives 3 were prepared in good yields by treatment of 4-amino-3-(4-chlorophenyl)-5-(pyridine- 4-yl)-4H-1,2,4-triazole (2) with selected aldehydes. Compounds 3 were reduced with NaBH4 to afford the corresponding 3-(4-chlorophenyl)-5-(pyridin-4-yl)-4-(arylmethylamino)-4H-1,2,4-triazole derivatives 4. Eighteen new compounds were synthesized and characterized by elemental analyses, IR, 1H NMR and 13C NMR spectral data. The compounds were screened for their antioxidant and antiradical activities.

Synthesis and biological activity studies of new hybrid molecules containing tryptamine moiety

The synthesis of N′-(4-substitutedphenylsulfonyl)-2-{4-[2-(1H-indol-yl)ethyl]-3-(4-chlorobenzyl)-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl}acetohydrazides (3a–c), 2-{4-[2-(1H-indol-3-yl)ethyl]-3-(4-chlorobenzyl)-5-oxo-4,5-dihydro-1H-1,2,4-triazol-1-yl}-N′-aryl methylidene acetohydrazides (4a–f) and 4-[2-(1H-indol-3-yl)ethyl]-5-(4-substitutedbenzyl)-2-[(5-sulfanyl-1,3,4-oxadiazol-2-yl)methyl]-2,4-dihydro-3H-1,2,4-triazol-3-ones (5a, b) was performed starting from the corresponding acid hydrazides (2a, b) which was reported earlier. The treatment of 1,3,4-oxadiazole derivatives (5a, b) with hydrazine hydrate produced 4-amino-5-sulfanyl-4H-1,2,4-triazol-3-yl derivatives (6a, b). Then, compound 6b was converted to the corresponding Schiff base (7) by the treatment with anisaldehyde. The synthesis of 5-(4-chlorobenzyl)-4-[2-(1H-indol-3-yl)ethyl]-2-[(4-benzyl-5-oxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)methyl]-2,4-dihydro-3H-1,2,4-triazol-3-one (8) and 5-(4-methylbenzyl)-4-[2-(1H-indol-3-yl)ethyl]-2-[(4-benzyl-5-oxo-4,5-dihydro-1H-1,2,4-triazol-3-yl)methyl]-2,4-dihydro-3H-1,2,4-triazol-3-one (10) was carried out by the reaction of acid hydrazides (2a, b) with aryl iso(thio)cyanates either via the formation of the intermediates (9a, b) (for 10) or direct cyclization (for 8). 1,3-Oxa(thia)zol-2(3H)-ylidene]acetohydrazide derivatives (11a, b) were obtained by the reaction of 9a, b with 4-chlorophenacyl bromide. All newly synthesized compounds were screened for their antimicrobial activities and some of which was found to be active against the test microorganisms.

Acetohydrazide Derivative for Selective Separation and Preconcentration of Cu(II) Ions by Coprecipitation Method Without Using a Carrier Element

ABSTRACT A simple and rapid procedure based on the combination of carrier element free coprecipitation (CEFC) and flame atomic absorption spectrometric (FAAS) determinations has been developed for selective separation and preconcentration of Cu(II) ions in some environmental solid (Turkish and import coffee) and liquid (sea and stream waters) samples. In this method, acetohydrazide derivative was used as an organic coprecipitant without adding any carrier element for coprecipitation of Cu(II) ions. The preconcentration factor was found to be 50, the limit of detection (LOD) was 0.31 µg L−1, while the relative standard deviation (RSD) was found to be 1.6% for Cu(II) ions.