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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 calix[4]arenes bearing ?-hydroxy amide units as membrane carriers for amino acid methyl esters(Springer, 2012) Durmaz, MustafaNovel chiral calix[4]arene derivatives functionalized at the lower rim have been prepared from the reaction of p-tert-butylcalix[4]arene diamine or acylhydrazine derivative with mandelic acid or hydroxyisovaleric acid. The structures of these receptors were characterized by FTIR, H-1, C-13 and 2D COSY NMR spectroscopy and elemental analysis. The transport of amino acid derivatives (phenylalanine, phenylglycine and tryptophan methyl ester hydrochlorides) was studied through bulk liquid membrane in the presence of chiral calix[4]arene derivatives. The receptors have been found to act as carriers for transport of aromatic amino acid methylesters from the aqueous source phase to the aqueous receiving phase. The transport rate and L/D selectivity of amino acid esters studied depend strongly upon the structure of the chiral receptors and guests. The best enantioselectivity was obtained in the case of phenylglycine methyl ester for all chiral carriers.Öğe Graphene-based recyclable and bifunctional heterogeneous chiral catalyst for direct asymmetric aldol reaction(Elsevier Science Sa, 2020) Azlouk, Manel; Durmaz, Mustafa; Zor, Erhan; Bingol, HalukApplication of metal-free heterogeneous asymmetric catalysis is of great interest in the field of asymmetric synthesis. Herein, two novel graphene-supported praline-based bifunctional carbocatalysts were prepared by post-grafting c-proline onto graphene oxide sheets via organoamine-functIonalized graphene oxide (GO-NH2) and reduced graphene oxide (GO-NH2). Different methods such as Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron spectroscopy (TEM) were employed to examine the surface functionalization of GO. The catalytic properties of these materials were investigated in the direct asymmetric aldol reaction. r-proline grafted heterogeneous catalyst, GO-Pro, was found to be an efficient and powerful organocatalyst for the enantioselective aldol reaction under mild conditions in hexane and afforded the corresponding aldol adducts with satisfactory isolated yields (up to 88%) and enantiomeric excesses (up to 85%). Furthermore, graphene-based carbocatalyst could be recovered and recycled easily by a simple washing procedure and re-used for several times without substantial reduction in its catalytic activity.Öğe A Novel Calix[4]arene Thiourea Decorated with 2-(2-Aminophenyl)benzothiazole Moiety as Highly Selective Chemical Gas Sensor for Dichloromethane Vapor(Wiley-V C H Verlag Gmbh, 2021) Durmaz, Mustafa; Acikbas, Yaser; Bozkurt, Selahattin; Capan, Rifat; Erdogan, Matem; Ozkaya, CansuA newly synthesized calix[4]arene thiourea derivative decorated with 2-(2-aminophenyl)benzothiazole unit is selected to take part important role in host-guest interactions of the macrocyclic molecules. p-tert-butylcalix[4]arene dithiourea (C[4]-DT) Langmuir-Blodgett (LB) thin films are prepared and characterized to develop a new sensing element for the detection of seven different organic vapors (dichloromethane, chloroform, acetone, benzene, carbon tetrachloride, toluene and m-xylene). The preparation of C[4]-DT-based thin films onto the different substrates was successfully and uniformly achieved with linear regressions of 0.9971 and 0.9954 for coating onto quartz glass and quartz crystal, respectively. The frequency shift (61.01 Hz) and the mass deposited onto quartz crystal (969.80 ng) were calculated for each layer. The swelling dynamics of C[4]-DT QCM chemical sensor was also illuminated by developing the early time Fick's diffusion equation. The sensing measurements can be concluded that owing to its high sensitivity (6.63 Hz/ppm), fast response and low detection limit (0.45 ppm), this proposed C[4]-DT LB coated sensor is expected to be promising alternative chemical sensor for detection of DCM vapor.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 A novel turn-on fluorometric reporter-spacer-receptor chemosensor based on calix[4]arene scaffold for detection of cyanate anion(Wiley, 2021) Bozkurt, Selahattin; Halay, Erkan; Durmaz, Mustafa; Topkafa, Mustafa; Ceylan, OzgurHerein, a novel calix[4]arene compound, which was modified by the 2-(2-aminophenyl)benzothiazole fragment with cyanate recognition function was designed based on the reporter-spacer-receptor sensing system. The construction was done via two-step reaction, and the desired sensor 4 was characterized by FT-IR, H-1-, C-13-NMR, and fluorescence spectroscopy along with HRMS data. The sensor candidate showed distinct fluorometric cyanate detection by means of reporter feature of selected benzothiazole constituent. In the presence of cyanate, the sensor gave a turn-on-type fluorescence at 482 nm with a large stokes' shift. Furthermore, it was observed that our fluoroionophore 4 is highly selective toward cyanate over remaining anions such as sulfate, phosphate, fluoride, chloride, bromide, iodide, chlorate, and nitrate in 10% aqueous solution of DMSO. The 1:2 stoichiometric ratio of the 4-cyanate complex was given the best fit with Job's plot based on the titration data. The association constant (K-a) of sensor 4 with cyanate is determined to be 1.64 x 10(5) M-2. The obtained limit of detection (LOD) value for cyanate anion, 312 nM, clearly revealed the remarkable sensitivity of the chemosensor 4. This supramolecular method provides a highly adaptive technique for the detection of cyanate and so cyanide ions by current international standard methods.Öğe Primary amine-thiourea grafted graphene-based heterogeneous chiral catalysts for highly enantioselective Michael additions(Elsevier, 2022) Badr, Sayed Mustafa; Azlouk, Manel; Zor, Erhan; Bingol, Haluk; Durmaz, MustafaHeterogeneous asymmetric catalysis based on earth-abundant carbon materials put together the advantages for the ease of separation, simple regeneration, and high stability of solid catalysts as well as acts as low-cost, environmentally friendly metal-free alternative to the metal-based catalysts. Two new bifunctional carbocatalysts [(S,S) and (R,R) GO-PATU] were prepared by anchoring enantiomerically pure organosilanes bearing primary amine and thiourea groups to the graphene oxide (GO) skeleton covalently via silane coupling reaction. The surface modification of GO was analyzed by a combination of Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron spectroscopy (TEM) techniques. The catalytic performances of graphene-based materials were investigated in the asymmetric Michael addition reactions of alpha,alpha-disubstituted-aldehydes to nitrostyrenes and N-substituted-maleimides. The effects of solvents and Bronsted basic or acidic additives were evaluated using both catalysts and good yields (up to 85%) and stereoselectivities (up to 95% ee) were obtained in dichloromethane at room temperature in the presence of L- and D-camphorsulfonic acid. Besides, recycling and reusing studies of the catalysts were successfully performed.Öğe A rapid responsive coumarin-naphthalene derivative for the detection of cyanide ions in cell culture(Academic Press Inc Elsevier Science, 2022) Aydin, Ziya; Keskinates, Mukaddes; Yilmaz, Bahar; Durmaz, Mustafa; Bayrakci, MevlutCyanide ion (CN-) is widely used in many industrial processes; however, it causes several diseases in humans. Therefore, rapid and accurate detection of CN- is very important and urgent. In this study, a CN- sensor (MH-2) which was capable of detecting CN- ions in living cell was developed. MH-2 gives a rapid color change, absorbance and fluorescence response to CN- in the presence of the anions tested in the working system. The binding ratio between the sensor and CN- was demonstrated by some spectrophotometric methods and the sensing mechanism was investigated by NMR titration experiments, suggesting that MH-2 gives response to CN- via the nucleophilic addition reaction. The fluorescence detection limit and the absorbance detection limit were calculated as 0.056 mu M and 0.11 mu M, respectively. Both of these detection limits are below the tolerable limit recommended by WHO for CN- in the drinking water (1.9 mu M). MH-2 was also applied to living cells for bio-imaging and the results showed that the sensor penetrates the cells and can detect cyanide ions in living cells.Öğe Recent applications of chiral calixarenes in asymmetric catalysis(Beilstein-Institut, 2018) Durmaz, Mustafa; Halay, Erkan; Bozkurt, SelahattinThe use of calixarenes in asymmetric catalysis is receiving increasing attention due to their tunable three-dimensional molecular platforms along with their easy syntheses and versatile modification at the upper and lower rims. This review summarizes the recent progress of synthesis and use of chiral calixarenes in asymmetric syntheses which emerged later than 2010.
