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Öğe Application of L-prolinamides as highly efficient organocatalysts for the asymmetric Michael addition of unmodified aldehydes to nitroalkenes(Pergamon-Elsevier Science Ltd, 2012) Naziroglu, Hayriye Nevin; Durmaz, Mustafa; Bozkurt, Selahattin; Demir, Ayhan Sitki; Sirit, AbdulkadirThe asymmetric Michael addition of aldehydes to nitroolefins was investigated using a combination of L-prolinamide derivatives and various acidic additives. (S)-1,1'-Bi-2-naphthol was found to be the most effective co-catalyst and afforded the nitroaldehyde products with excellent yields (up to 95%), enantiomeric excesses (up to 99%) and diastereoselectivity ratios (up to 99:1). (C) 2012 Elsevier Ltd. All rights reserved.Öğe Calixarene-based chiral primary amine thiourea promoted highly enantioselective asymmetric Michael reactions of ?,?-disubstituted aldehydes with maleimides(Pergamon-Elsevier Science Ltd, 2013) Durmaz, Mustafa; Sirit, AbdulkadirCalix[4]arene based chiral bifunctional thiourea-primary amines have been shown to act as effective catalysts for the Michael addition of aldehydes to maleimides for the first time. The corresponding adducts were generally obtained preferentially in (R)- or (S)-forms with high yields (up to 99%) and with high to excellent enantioselectivities (up to 98% ee). (C) 2013 Elsevier Ltd. All rights reserved.Öğe Calixarene-based highly efficient primary amine-thiourea organocatalysts for asymmetric Michael addition of aldehydes to nitrostyrenes(Taylor & Francis Ltd, 2013) Durmaz, Mustafa; Sirit, AbdulkadirThe synthesis of calix[4]arene-based chiral bifunctional primary aminethiourea catalysts has been described from p-tert-butylcalix[4]arene for the first time. The calix[4]arene-based catalysts were successfully applied to promote Michael addition of aldehydes with nitroalkenes affording preferentially the (R)- or (S)-adducts in high yields (up to 95%) and excellent enantioselectivities (up to 99% ees).Öğe Calixarene-derived chiral tertiary amine-thiourea organocatalyzed asymmetric Michael additions of acetyl acetone and dimethyl malonate to nitroolefins(Pergamon-Elsevier Science Ltd, 2016) Durmaz, Mustafa; Tataroglu, Aysun; Yilmaz, Horu; Sirit, AbdulkadirNovel bifunctional chiral thiourea-tertiary amines bearing a calix[4]arene scaffold were synthesized and applied in catalytic asymmetric Michael addition of acetyl acetone and dimethyl malonate to nitroolefins. The corresponding adducts were obtained in excellent yields (up to 99%) and with high enantioselectivities (up to 94% ee). (C) 2016 Elsevier Ltd. All rights reserved.Öğe Chiral tetraoxacalix[2]arene[2]triazine-based organocatalysts for Enantioselective Aldol reactions(Pergamon-Elsevier Science Ltd, 2019) Genc, Hayriye Nevin; Ozgun, Ummu; Sirit, AbdulkadirNovel efficient chiral tetraoxacalix[2]arene[2]triazine-based organocatalysts have been designed and synthesized from the reaction of tetraoxacalix[2]arene[2]triazine with R/S-phenylethylamine or R/S-1-naphthylethylamine for the Aldol reaction of acetone with aromatic aldehydes to furnish the Aldol adducts in 71-92% yields with excellent enantioselectivities (78-99%). (C) 2019 Elsevier Ltd. All rights reserved.Öğe Design, synthesis and application of chiral tetraoxacalix[2]arene[2]triazine-based organocatalysts in asymmetric Michael addition reactions(Wiley, 2019) Genc, Hayriye Nevin; Ozgun, Ummu; Sirit, AbdulkadirA novel type of oxacalix[2]arene[2]triazine-based organocatalysts for asymmetric Michael reactions are reported for the first time. Chiral subunits were attached to the heteroatom-bridged calixaromatic platform by a reaction of (R)- and (S)-1-aminotetraline with tetraoxacalix[2]arene[2]triazine in both enantiomeric forms. To evaluate the catalytic efficiency of the novel organocatalysts, isobutyraldehyde reacted with various substituted and unsubstituted aromatic trans-beta-nitrostyrenes in tetrahydrofuran (THF), leading to Michael adducts in excellent yields and enantioselectivites (up to 97% yield and 99% ee).Öğe Fabrication and characterization of calix[4]arene Langmuir-Blodgett thin film for gas sensing applications(Springer, 2017) Acikbas, Yaser; Bozkurt, Selahattin; Halay, Erkan; Capan, Rifat; Guloglu, Mehmet Levent; Sirit, Abdulkadir; Erdogan, MatemIn this work, the Langmuir-Blodgett (LB) technique was applied onto the different substrates such as quartz, quartz crystals and gold coated glass for fabricating LB thin films with 25,27-(Dipropylmorpholinoacetamido)-26,28-dihydroxycalix[4]arene. The characteristics of the calix[4]arene LB films were evaluated by UV-Vis, atomic force microscopy (AFM), quartz crystal microbalance (QCM) and surface plasmon resonance (SPR) measurements. The mass deposited on the quartz crystal per bilayer was predicted as 2028.80 ng (7.65 ng mm(-2)) for the calix[4]arene LB film. The sensing abilities of this LB film towards the development of room temperature organic vapor sensing devices were also examined. QCM and SPR systems were fixed to investigate vapor sensing performance of macrocyclic LB films during exposure to volatile organic compounds (VOCs). The macrocyclic LB thin films were more sensitive to dichloromethane than other vapors. The sensitivity and detection limit values of the calix[4]arene QCM sensor to dichloromethane vapor were calculated as 2.023 Hz ppm(-1) and 1.482 ppm, respectively. The sensitivities of the calix[4]arene LB films against organic vapors can be explained with the host-guest interaction between the cavity of molecule and the organic vapor molecules. It is determined that the calix[4]arene LB film is more sensitive to dichloromethane than other vapors at room temperature and the calix[4]arene is a promising material serving as a vapor sensing device.Öğe Naked-eye colorimetric and switch-on fluorescence chemosensor based on a rhodamine derivative for Hg2+: Smartphone device, test-kit and food sample applications(Elsevier Science Sa, 2023) Genc, Hayriye Nevin; Yasar, Ozlem Guctekin; Elmas, Sukriye Nihan Karuk; Arslan, Fatma Nur; Yilmaz, Ibrahim; Sirit, AbdulkadirA new rhodamine-based switch-on fluorescent and colorimetric chemosensor (RHEN) was fabricated for the determination of Hg2+. The RHEN showed a noticeable colorimetric response for Hg2+ from colorless to pink under daylight. When exposed to Hg2+, the fluorescence at 582 nm from the probe RHEN was remarkably enhanced, attend by a color change from colorless to dusty rose color under 365 nm UV lamp. The RHEN had a notable specificity and selectivity for Hg2+ and depicted an excellent sensing performance for detecting lowly concentrated Hg2+ (LOD; 0.11 mu M). The binding phenomenon between RHEN and Hg2+ was identified by Job's method, MALDI TOF-MS and FT-IR spectroscopy. Moreover, the fabricated chemoprobe RHEN was not only utilized to identify Hg2+ in fish samples with satisfactory results (95.28-111.66 %) but also was successfully used for test-paper and cotton swab applications. Smartphone application also showed that RHEN could be used as a potent tool for on-site sensing of Hg2+ without the need for complicated device.Öğe Novel and highly efficient bifunctional calixarene thiourea derivatives as organocatalysts for enantioselective Michael reaction of nitroolefins with diketones(Springer, 2018) Genc, Hayriye Nevin; Sirit, AbdulkadirNew bifunctional calixarene thiourea organocatalysts were synthesized and applied in catalytic asymmetric Michael addition of acetylacetone to various nitroolefins at room temperature. The corresponding adducts were obtained in good to excellent yields with excellent enantioselectivities (up to 92% ee). The present research demonstrates the advantages of incorporating two stereocontrolling structures into a single catalyst. Notably, it offers a simple and convenient doubly stereocontrolled approach for the catalytic asymmetric synthesis of a chiral organic molecule.Öğe A novel calix[4]arene-based bifunctional squaramide organocatalyst for enantioselective Michael addition of acetylacetone to nitroolefins(Royal Soc Chemistry, 2016) Vural, Ummu; Durmaz, Mustafa; Sirit, AbdulkadirA new chiral calix[4]arene-based organocatalyst 3 bearing bis-squaramide moieties was designed and synthesized from p-tert-butylcalix[4] arene. This bifunctional squaramide organocatalyst was used in the enantioselective conjugate addition of acetylacetone to beta-nitrostyrenes. The corresponding adducts were obtained in good to excellent yields with high enantioselectivities (up to 94% ee).Öğe Novel efficient bifunctional calixarene thiourea organocatalysts: synthesis and application in the direct enantioselective aldol reactions(Pergamon-Elsevier Science Ltd, 2016) Genc, Hayriye Nevin; Sirit, AbdulkadirNovel efficient bifunctional calixarene thiourea organocatalysts have been designed as efficient organocatalysts for direct asymmetric aldol reactions between acetone and aromatic aldehydes. The reactions generated the corresponding products in satisfactory isolated yields (up to 96%) and with excellent enantiomeric excesses (up to 99%) in the presence of catalyst (10 mol %). (C) 2016 Elsevier Ltd. All rights reserved.Öğe Optical and Vapor Sensing Properties of Calix[4]arene Langmuir-Blodgett Thin Films with Host-Guest Principles(Taylor & Francis Inc, 2018) Acikbas, Yaser; Bozkurt, Selahattin; Erdogan, Matem; Halay, Erkan; Sirit, Abdulkadir; Capan, Rifat25,27-(Dipropylmorpholinoacetamido)-26,28-dihydroxycalix[4]arene was used as a chemical sensor material in this work. The calix[4]arene LB thin films were prepared onto a gold-coated glass and quartz glass substrates to fabricate a thin film chemical sensor element. Atomic Force Microscopy (AFM) and Surface Plasmon Resonance (SPR) techniques were used to characterize all the calix[4]arene LB thin films. The film thickness and the refractive index of thin films can be evaluated with the fitted experimental SPR datas. The refractive index and the thickness per monolayer of LB films were determined as a 1.58 +/- 0.04 and 1.27 +/- 0.09nm, respectively. The calix[4]arene LB thin film chemical sensor element was exposed to dichloromethane, chloroform, benzene and toluene vapors. The SPR kinetic measurements displayed that, the photodetector response change, I-rf for saturated dichloromethane vapor is much larger than the other vapors with the I-rf value of 48 au and the diffusion coefficient value of 5.1 x 10(-16) cm(2)s(-1). Swelling process was analyzed by well known Fick's Equations. In this approach diffusion coefficients for swelling were conformed to the square root of time and were correlated with the volatile organic compounds. Our results showed that calix[4]arene thin film has a highly selective with a large response to dichloromethane vapor.Öğe Synthesis and application of L-proline and R-phenylglycine derived organocatalysts for direct asymmetric Michael addition of cyclohexanone to nitroalkenes(Tubitak Scientific & Technological Research Council Turkey, 2012) Naziroglu, Hayriye Nevin; Sirit, AbdulkadirNovel R-phenylglycine derived organocatalysts were prepared from the reaction of Cbz-R-phenylglycine with indoline, pyrrolidine, or (S)-(-)-2-(diphenylmethyl) pyrrolidine in 3 steps. The asymmetric Michael addition of cyclohexanone to nitroolefins was investigated using R-phenylglycine derivatives along with L-prolinamides as chiral catalysts. The desired products were obtained in excellent yields with enantioselectivities up to 90% ee and diastereomeric ratio up to 98:2 of the syn addition product.Öğe A tetraoxacalix[2]arene[2]triazine based fluorogenic probe for the sensing of Fe3+: Computational and living-cell imaging applications(Elsevier Science Sa, 2020) Karuk Elmas, Sukriye Nihan; Gunay, Ibrahim Berk; Genc, Hayriye Nevin; Aydin, Duygu; Arslan, Fatma Nur; Sadi, Gokhan; Sirit, AbdulkadirHerein, we have reported a feasibility study of highly selective and sensitive fluorogenic chemosensor (probe TOCT) derived from tetraoxacalix [2] arene [2] triazine for Fe3+ sensing in aqueous media. The probe TOCT has been fabricated and verified by H-1-NMR, HR-LCMS,FT-IRand C-13-NMR. The sensing properties of probe TOCT toward various metal ions were confirmed by fluorescence titration study as well as competitive study. The intensity of probe TOCT reduced with the amount of Fe3+ when it was excited at 300 nm in CH3CN:H2O (95/5, v/v, pH = 7) media. The probe demonstrated a 'turn-off' response toward Fe3+, in the presence of possible competing ions. The detection limit value of probe TOCT for Fe3+ sensing was computed to be 12.5 nM. The possible molecular structure of complex between probe TOCT and Fe3+ was also proposed on the basis of HR-LCMS and FT-IR. The stoichiometry of TOCT-Fe3+ complex was identified to be 1:1 to the methodology of Job's plot. The binding ability was studied through the equation of Benesi-Hildebrand which was computed to be 8.90 x 10(4) M-1 for Fe3+. To support the intensity enhancement and quenching studies, we reported computational experiments based on the density functional theory (DFT). Moreover, a great potential has been detected for probe TOCT as a fluorescent chemosensor in biological applications to monitor Fe3+ in living cells.
