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    Carbon-carbon bond formation catalyzed by PEPPSI Pd-NHC
    (Elsevier Science Sa, 2017) Akkoc, Senem; Ilhan, Ilhan Ozer; Gok, Yetkin; Kayser, Veysel
    Five new palladium complexes were efficiently synthesized from the reaction of benzimidazolium salts, potassium carbonate (K2CO3) and palladium chloride (PdCl2) in pyridine (for 3-5) or 3-chloropyridine (for 6 and 7). The synthesized complexes were characterized and tested in Suzuki-Miyaura cross-coupling reaction as catalysts. In the presence of catalysts 3-7, biaryl products were obtained in moderate yields when phenylboronic acid was used as boronic acid derivative. However, the coupling of thianaphthene-2-boronic acid with 1-chloro-4-nitrobenzene generated low yields although a longer period of time was used in comparison to the coupling of phenylboronic acid with aryl chlorides. (C) 2017 Elsevier B.V. All rights reserved.
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    In situ Generation of Efficient Palladium N-heterocyclic Carbene Catalysts Using Benzimidazolium Salts for the Suzuki-Miyaura Cross-coupling Reaction
    (Bentham Science Publ Ltd, 2016) Akkoc, Senem; Gok, Yetkin; Ilhan, Ilhan Ozer; Kayser, Veysel
    Five new unsymmetrically substituted salts containing a benzimidazole backbone were synthesized in high yields and their structures were verified via spectroscopic and analytical methods such as HRMS, 1D and 2D NMR spectroscopy, FT-IR and elemental analysis. The catalytic properties of all the synthesized salts were tested in a homogeneous Suzuki-Miyaura cross-coupling reaction to get coupling products in high efficiencies with low amounts of in situ formed catalysts. In this reaction, the couplings of boronic acid derivatives with different aryl chlorides were made in the presence of palladium acetate, 2-6 and base at various times and temperatures. According to the obtained results, the benzimidazolium salts which are N-heterocyclic carbene (NHC) ligand precursors were found to have high catalytic activity. In particular, the coupling of 4-chlorotoluene with phenylboronic acid was obtained in very high yield and conversion in the catalyzed Pd-NHC complexes which were in situ formed from compounds 3 and 6 and Pd(OAc)(2).
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    In vitro cytotoxic activities of new silver and PEPPSI palladium N-heterocyclic carbene complexes derived from benzimidazolium salts
    (Elsevier Science Sa, 2016) Akkoc, Senem; Ilhan, Ilhan Ozer; Gok, Yetkin; Upadhyay, Parth J.; Kayser, Veysel
    New benzimidazolium salts (2, 3) and their silver (4, 5) and palladium (6, 7) N-heterocyclic carbene (Ag-and Pd-NHC) complexes were designed, synthesized and structurally characterized by NMR (H-1 and C-13), IR, HRMS and UV-Vis spectroscopic methods. All the synthesized compounds were tested in human colon cancer (DLD-1), breast cancer (MDA-MB-231) and embryonic kidney (HEK 293T) (non-cancerous) cell lines for in vitro cytotoxicity. Compound 4 specifically showed low IC50 values for these cell lines (IC50 values 12.41 +/- 2.89, 11.98 +/- 2.52 and 4.21 +/- 1.74 mu mol/L in DLD-1, MDA-MB-231 and HEK 293T cell lines, respectively). The Pd-NHC complexes (6, 7) did not exhibit cytotoxic activity (IC50 values > 200 in DLD-1, MDA-MB-231, HEK 293T cell lines). Therefore, Ag-NHC complexes can be further investigated as potential anticancer agents. (C) 2016 Elsevier B. V. All rights reserved.
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    N-Methylphthalimide-substituted benzimidazolium salts and PEPPSI Pd-NHC complexes: synthesis, characterization and catalytic activity in carbon-carbon bond-forming reactions
    (Beilstein-Institut, 2016) Akkoc, Senem; Gok, Yetkin; Ilhan, Ilhan Ozer; Kayser, Veysel
    A series of novel benzimidazolium salts (1-4) and their pyridine enhanced precatalyst preparation stabilization and initiation (PEPPSI) themed palladium N-heterocyclic carbene complexes [ PdCl2(NHC)(Py)] (5-8), where NHC = 1-(N-methylphthalimide)3- alkylbenzimidazolin-2-ylidene and Py = 3-chloropyridine, were synthesized and characterized by means of H-1 and C-13{H-1} NMR, UV-vis (for 5-8), ESI-FTICR-MS (for 2, 4, 6-8) and FTIR spectroscopic methods and elemental analysis. The synthesized compounds were tested in Suzuki-Miyaura cross-coupling (for 1-8) and arylation (for 5-8) reactions. As catalysts, they demonstrated a highly efficient route for the formation of asymmetric biaryl compounds even though they were used in very low loading. For example, all compounds displayed good catalytic activity for the C-C bond formation of 4-tert-butylphenylboronic acid with 4-chlorotoluene.
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    New compounds based on a benzimidazole nucleus: synthesis, characterization and cytotoxic activity against breast and colon cancer cell lines
    (Elsevier Science Sa, 2017) Akkoc, Senem; Kayser, Veysel; Ilhan, Ilhan Ozer; Hibbs, David E.; Gok, Yetkin; Williams, Peter A.; Hawkins, Bryson
    Benzimidazolium salts and their Pyridine Enhanced Precatalyst Preparation Stabilization and Initiation (PEPPSI) palladium N-heterocyclic carbene (Pd-NHC) based complexes have been synthesized and their structures characterized with a number of different instrumental techniques including NMR (H-1 and C-13), IR, EI-MS (for 2), X-ray (for 1, 2 and 4) and elemental analysis. The cytotoxicity of all the compounds was tested using the human embryonic kidney (HEK-293T), human breast epithelial adenocarcinoma (MDA-MB-231), and human colon epithelial colorectal adenocarcinoma (DLD-1) cell lines. The benzimidazolium salts (2-5) had more cytotoxic activity against cancerous cells compared with the metal complexes (6-9), which curiously exhibited no activity against any of the cell lines. Based on the IC50 values, compound 5 displayed the highest in vitro anticancer activity among compounds 2-9. Crown Copyright (C) 2017 Published by Elsevier B.V. All rights reserved.