Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 21Citation - Scopus: 21Palladium-Catalyzed Alkoxycarbonylation of Conjugated Enyne Oxiranes: a Diastereoselective Method for the Synthesis of 7-Hydroxy(American Chemical Society, 2015) Kuş, Melih; Artok, Levent; Aygün, MuhittinPalladium-catalyzed alkoxycarbonylative 1,5-substitution of conjugated enyne oxiranes provides a diastereoselective route to (E)-configured 7-hydroxy-2,3,5-trienoates. The reactions proceeded in a highly stereoselective manner, possibly through sequential formation of π-allylpalladium and σ-vinylallenyl palladium complexes. The major diastereomeric form of the product is determined by the configuration of the alkenyl moiety of the substrate.Article Citation - WoS: 21Citation - Scopus: 21Regio- and Stereoselective Synthesis of 2,3,5-Trienoates by Palladium-Catalyzed Alkoxycarbonylation of Conjugated Enyne Carbonates(American Chemical Society, 2014) Karagöz, Ezgi Şule; Kuş, Melih; Akpınar, Gürkan Eray; Artok, LeventPalladium-catalyzed carbonylation of 2,4-enyne carbonates in an alcohol and under balloon pressure of CO proceeds through 1,5-substitution to yield (E)-2,3,5-trienoates. The olefin geometry of the substrate is important to control the overall stereochemistry of this alkoxycarbonylation method. The reaction proceeds through successive formation of π-allylpalladium with an R3 group oriented syn and σ-allenyl palladium complexes.Article Citation - WoS: 7Citation - Scopus: 7Rhodium-Catalysed Alkoxycarbonylative Cyclisation Reactions of 1,6-Enynes(John Wiley and Sons Inc., 2011) Ziyanak, Fırat; Kuş, Melih; Artok, LeventThe rhodium-catalysed carbonylation of 1,6-enynes possessing an electron-deficient alkenyl moiety in an alcohol reagent in the presence of a rhodium complex proceeded stereo- and chemoselectively to afford exocyclic α,β-enoates.Article Citation - WoS: 14Citation - Scopus: 15Rhodium- and Palladium-Catalyzed 1,5-Substitution Reactions of 2-En Acetates and Carbonates With Organoboronic Acids(American Chemical Society, 2011) Üçüncü, Muhammed; Karakuş, Erman; Kuş, Melih; Akpınar, Gürkan Eray; Aksın Artok, Özge; Krause, Norbert; Karaca, Sıla; Elmaci, Nuran; Artok, LeventTwo methods involving the rhodium-catalyzed reaction of 2-en-4-yne acetates and the palladium-catalyzed reaction of 2-en-4-yne carbonates with organoboronic acids were investigated; both afforded exclusively the (E)-configured vinylallenes. The coordinative interaction of the rhodium with the acetate group promoted the δ-elimination of Rh(I)-OAc from the alkenylrhodium intermediate II in both syn and anti modes, with the syn-elimination being the major path. DFT calculations revealed that a conformer of this intermediate (II), which can lead to the (E)-configured vinylallene product via the syn-elimination mode, is energetically the most favorable conformer. The rhodium-catalyzed procedure is not applicable to reactions involving (E)-configured enyne acetates, because the geometry of the alkenylrhodium intermediate that is derived from the corresponding (E)-enyne acetate would not allow such coordinative interaction to occur. The palladium-catalyzed method, which proceeds through formation of the σ-vinylallenylpalladium intermediate, B, is suitable for both the (E)- and (Z)-configured enyne carbonates and appears to have a wider scope for both organoboronic acids and enyne substrates. The palladium-catalyzed reaction of an enantiomerically enriched enyne carbonate proceeded with racemization.Article Citation - WoS: 37Citation - Scopus: 38Palladium-Catalyzed Alkoxycarbonylation of (z)-2 Carbonates Leading To 2,3,5-Trienoates(American Chemical Society, 2011) Akpınar, G. Eray; Kuş, Melih; Üçüncü, Muhammed; Karakuş, Erman; Artok, LeventPd(0)-catalyzed carbonylation of (Z)-2-en-4-yn carbonates in the presence of a balloon pressure of CO in an alcohol donates vinylallenyl esters with an exclusively E-configuration and in high yields. The fact that no such reactivity could be observed with E-configured enyne carbonates may indicate that the reaction is promoted via the cooperative coordination of palladium with both alkynyl and carbonate moieties.Article Citation - WoS: 4Citation - Scopus: 6The Effect of Additives on Hydrodesulfurization of Dibenzothiophene Over Bulk Molybdenum Sulfide: Increased Catalytic Activity in the Presence of Phenol(Elsevier Ltd., 2008) Gül, Ömer; Atanur, Osman M.; Artok, Levent; Erbatur, OktayThe effect of various additive organic reagents on the activation of MoS3 as molybdenum sulfide catalyst precursor during hydrodesulfurization reaction of dibenzothiophene was studied. It was found that the presence of phenol or 1-naphthol greatly promoted the activity of the catalyst, while tetralin, 9,10-dihydrophenanthrene, ethylbenzene, and pyridine reagents were found to be detrimental for the activity of the catalyst.Article Citation - WoS: 167Citation - Scopus: 197Preparation and Characterization of Activated Carbons by One-Step Steam Pyrolysis/Activation From Apricot Stones(Elsevier Ltd., 2006) Şentorun-Shalaby, Çiğdem; Uçak Astarlıoğlu, Mine G.; Artok, Levent; Sarıcı, ÇiğdemThe activated carbons were prepared from Malatya (a city located in the south-east of Turkey) apricot stones by one-step steam pyrolysis/activation process and characterized for their pore structures. Three kinds of apricot stones that differ in their sulfur content, because of the different drying processes, were chosen for this study to investigate the effect of sulfur in the activated carbon production. The effect of process variables, such as activation temperature, soak time, and particle size range was studied on these samples. The activation temperature and time tested were in the ranges of 650-850 °C for 1-4 h. The activated carbons were evaluated for their chemical (elemental composition), surface (BET surface area, mercury porosimetry), and adsorption (iodine number) properties. Carbonization behavior of the apricot stones was investigated by thermogravimetric analysis. Scanning electron microscopy (SEM) was used to follow the changes in the carbon texture upon activation. The experimental results revealed that carbons obtained by the same conditions of activation show differences in their pore structures and adsorption characteristics due to their sulfur contents. The highest BET surface area carbon (1092 m2/g) was obtained from the low sulfur content (0.04%) apricot stone with a particle size range of 1-3.35 mm at the activation conditions of 800 °C for 4 h. The experimental results showed that commercial production of porous activated carbons from Malatya apricot stones is feasible in Turkey.Article Citation - WoS: 23Citation - Scopus: 28Direct Liquefaction of High-Sulfur Coals: Effect of the Catalyst, the Solvent, and the Mineral Matter(American Chemical Society, 2002) Gözmen, Belgin; Artok, Levent; Erbatur, Gaye; Erbatur, OktayTwo low-rank coals with high sulfur contents (Gediz subbituminous coal: 7.6 wt % S:dry basis. Çayirhan lignite: 5.7 wt% S:dry basis.) were subjected to hydroliquefaction. Liquefaction conditions included dry or solvent mediated runs under pressurized hydrogen without added catalyst or with the impregnated catalyst precursor ammonium heptamolybdate (AHM). Gediz coal having higher sulfur content gave 90% conversion in the absence of catalyst and solvent. Maximum conversion (98%) and maximum oil + gas yield (70%) from this coal were obtained by impregnating AHM onto coal and carrying out liquefaction in H 2/tetralin system at 450 °C for 30 min. Under the same conditions, Çayirhan lignite gave 85% conversion and 70.5% oil + gas yield. The superior hydrodesulfurization effect of impregnated AHM on the oil fraction when used in the absence of solvent (less than 0.1% S in lignite's oil and less than 1% S in subbituminous coal's oil following one-stage hydrogenation) is a promising finding of this work. AHM was found to be much more effective in liquefaction of Çayirhan lignite and this has been ascribed to the well-dispersion of AHM throughout this lignite's structure via a cation-exchange mechanism through oxygen functionalities. Strong evidence for the catalytic effect of clay minerals in coal structure on char-forming reactions during liquefaction was observed by making use of liquefaction reactions of demineralized coal samples. It was also observed that tetralin had a retarding effect on the condensation and subsequent cross-linking reactions.Article Citation - WoS: 78Citation - Scopus: 83Synthesis, Characterization and Application of a Novel Sorbent, Glucamine-Modified Mcm-41, for the Removal/Preconcentration of Boron From Waters(Elsevier Ltd., 2005) Kaftan, Öznur; Açıkel, Müge; Eroğlu, Ahmet Emin; Shahwan, Talal; Artok, Levent; Ni, ChaoyingA novel sorbent was prepared by the functionalization of an inorganic support material, MCM-41, with N-methylglucamine for the uptake of boron from aqueous solutions prior to its determination by inductively coupled plasma optical emission spectrometry (ICP–OES). Characterization of the newly synthesized material was performed using BET, XRD, TEM, SEM and DRIFTS techniques, in addition to its C and N elemental content. Sorption behavior of the novel sorbent for boron was also investigated and found to obey Freundlich and Dubinin–Radushkevich (D–R) isotherm models. The maximum amount of B (as H3BO3) that can be sorbed by the sorbent was calculated from the D–R isotherm and was found to be 0.8 mmol B g−1 of sorbent. The applicability of the new sorbent for the removal/preconcentration of boron from aqueous samples was examined by batch method. It was found that the sorbent can take up 85% of boron in 5 min whereas quantitative sorption is obtained in 30 min. Any pH greater than 6 can be used for sorption. Desorption from the sorbent was carried out using 1.0 M HNO3. The sorption efficiency of the new sorbent was also compared to that of Amberlite IRA 743, a commercial resin with N-methylglucamine functional groups. Within the experimental conditions employed, the new sorbent was found to have higher sorption efficiency than the commercial resin. For method validation, spike recovery tests were performed at various concentration levels in different water types and were found to be between 83–95 and 75–92% for ultra pure water and geothermal water, respectively.