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Öğe Anion Extraction Properties of a New "Proton-Switchable" Terpyridin-Conjugated Calix[4]arene(AMER CHEMICAL SOC, 2014) Sayın, Serkan; Eymur, Serkan; Yılmaz, MustafaA new terpyridin-conjugated calix[4]arene derivative has been synthesized via selectively substitution of p-tert-butylcalix[4]arene. The synthesized ligand was characterized by FTIR, H-1 NMR, C-13 NMR, C-13-DEPT-135 and elemental analysis. Moreover, the dichromate extraction capability of the compound regarding the removal of toxic oxyanion from aqueous solutions was discussed in a liquid-liquid extraction system. The results indicated that the pH of the solution is a key parameter for the efficient extraction of Cr(VI) and that compound 6 is partially protonated in acidic conditions. Hence, facilitating binding of dichromate results from both electrostatic interactions and hydrogen bonding. To understand the selectivity of 6, the retention of dichromate anions in the presence of NO3-, Cl-, and SO42- anions at pH 1.5 was also discussed.Öğe Calixarene-proline functionalized iron oxide magnetite nanoparticles (Calix-Pro-MN): An efficient recyclable organocatalyst for asymmetric aldol reaction in water(ELSEVIER SCIENCE BV, 2015) Akceylan, Ezgi; Uyanık, Arzu; Eymur, Serkan; Şahin, Özlem; Yılmaz, MustafaCalix[4]arene-based chiral organocatalyst derived from L-proline supported onto well-defined (15 +/- 3 nm) magnetic Fe3O4 nanoparticles was used as a highly active, recoverable, and reusable catalyst for the asymmetric aldol reaction in water without need for organic solvents. The chiral organocatalyst showed high catalytic activity (up to 94%), enantioselectivity (up to 93%) and diastereoselectivity (up to 97:3) for the reaction between cyclohexanone and aromatic aldehydes. The catalyst could easily separated using an external magnetic field and reused for several times without any significant loss of activity. (C) 2015 Elsevier B.V. All rights reserved.Öğe Chiral Calix[4]arenes-Bearing Prolinamide Functionality as Organocatalyst for Asymmetric Direct Aldol Reactions in Water(TAYLOR & FRANCIS LTD, 2018) Şahin, Özlem; Eymur, Serkan; Uyanık, Arzu; Akceylan, Ezgi; Yılmaz, MustafaThe chiral calix[4]arene derivative (6) bearing an L-prolinamido group has been designed and proved to be a water compatible efficient organocatalysts for a direct enantioselective aldol reaction. Compound 6 catalyzes the aldol reaction of cyclohexanone and a variety of aromatic aldehydes yielding anti-aldol products in high yield with enantioselectivities of up to 93% and diastereoselectivity of up to 95:5.Öğe Direct enantioselective aldol reactions catalyzed by calix[4]arene-based L-proline derivatives in the water(PERGAMON-ELSEVIER SCIENCE LTD, 2014) Eymur, Serkan; Akceylan, Ezgi; Şahin, Özlem; Uyanık, Arzu; Yılmaz, MustafaTwo novel p-tert-butylcalix[4]arene-based chiral organocatalysts derived from L-proline have been developed to catalyze direct aldol reactions between cyclohexanone and aromatic aldehydes in water. Under the optimal conditions, high yields (up to 95%), enantioselectivities (up to 90%), and moderate diastereoselectivities (up to 65:35) were obtained. Considering the catalytic inefficiency of sole proline for the aldol reaction in water, these results clearly display the enormous effect of the hydrophobic part of calix[4]arene of compound A. (C) 2014 Elsevier Ltd. All rights reserved.Öğe L-proline derivatives based on a calix[4]arene scaffold as chiral organocatalysts for the direct asymmetric aldol reaction in water(TAYLOR & FRANCIS LTD, 2016) Aktaş, Mehmet; Uyanık, Arzu; Eymur, Serkan; Yılmaz, MustafaA new series of water-compatible proline catalysts (4-6) derived from calixarene bearing a hydrophobic nature have been synthesised. It was found that the compound 4 was a highly efficient organocatalyst for aldol reactions occurred in the water. Under optimised reaction conditions, high yields (up to 82%), good enantioselectivities (ee up to 81%) and high diastereoselectivities (dr up to 91:9) were obtained.Öğe Proline-calixarene thiourea host-guest complex catalyzed enantioselective aldol reactions: from nonpolar solvents to the presence of water(PERGAMON-ELSEVIER SCIENCE LTD, 2014) Demircan, Ezgi; Eymur, Serkan; Demir, Ayhan SitkiA proline-calix[4]arene thiourea host-guest complex catalyzed intermolecular aldol reaction of aromatic aldehydes with cyclohexanone has been developed. The anti-configured products were obtained in good yields and with high enantioselectivities. The reaction is proposed to work via a modified Houk-List model, where the carboxylate part of the praline constitutes as a supramolecular system with the thiourea. The outcome of the study indicates the influence of the calix[4]arene thiourea on both the reactivity and selectivity in a non-polar reaction medium, even in the presence of water at moderate temperatures. (C) 2014 Elsevier Ltd. All rights reserved.Öğe Self-condensation reactions of acyl phosphonates: synthesis of tertiary O -protected ?-hydroxyphosphonates(2014) Eymur, Serkan; Göllü, Mehmet; Demir, Ayhan SıtkıThe self-condensation reaction of benzoyl dialkyl phosphonates was developed using cyanide ion as catalyst, affording versatile tertiary O -protected α -hydroxy phosphonates in moderate yield.Öğe Self-condensation reactions of acyl phosphonates: synthesis of tertiary O-protected alpha-hydroxyphosphonates(SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY-TUBITAK, 2014) Eymur, Serkan; Gollu, Mehmet; Demir, Ayhan SitkiThe self-condensation reaction of benzoyl dialkyl phosphonates was developed using cyanide ion as catalyst, affording versatile tertiary O-protected alpha-hydroxy phosphonates in moderate yield.Öğe Umpolung strategy: Advances in catalytic C-C bond formations(SCIENTIFIC TECHNICAL RESEARCH COUNCIL TURKEY-TUBITAK, 2013) Eymur, Serkan; Gollu, Mehmet; Tanyeli, CihangirThis mini-review examines the recent advances in umpolung strategy, devised originally by Corey and Seebach. Although numerous stoichiometric variants have been published to date, this article covers just the catalytic C-C bond forming reactions due to their major benefits such as atom economy, less pollution, and workable simplicity. In the context of umpolung, the studies are evaluated under 3 main titles: enzyme, N -heterocyclic carbene, and cyanide ion catalyzed reactions. In particular, enzyme and NHC catalyzed reactions mainly involve asymmetric applications.Öğe Upper rim-functionalized calix[4]arene-based L-proline as organocatalyst for direct asymmetric aldol reactions in water and organic media(PERGAMON-ELSEVIER SCIENCE LTD, 2014) Uyanık, Arzu; Bayrakçı, Mevlüt; Eymur, Serkan; Yılmaz, MustafaThe synthesis of upper rim-functionalized calix[4]arene-based L-proline was described, and its catalytic efficiency as organocatalyst for the enantioselective aldol reaction in water was investigated. The results showed that the nature of the hydrophobic cavity of calixarene is critical for catalytic activity in water. The products of the reaction between various ketones and aldehydes with anti-configuration were obtained in high yields (up to 94%) with high diastereo- (up to 95:5 dr) and enantioselectivities (up to 80% ee). (C) 2014 Elsevier Ltd. All rights reserved.
