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Öğe Asymmetric transfer hydrogenation of acetophenone derivatives with novel chiral phosphinite based ?6-p-cymene/ruthenium(II) catalysts(Elsevier Science Sa, 2011) Aydemir, Murat; Meric, Nermin; Baysal, Akin; Turgut, Yilmaz; Kayan, Cezmi; Seker, Sevil; Togrul, MahmutEnantioselective reduction of prochiral ketones to optically active secondary alcohols is an important subject in synthetic organic chemistry because the resulting chiral alcohols are extremely useful, biologically active compounds. The new chiral ligands (2R)-2-[benzyl{(2-((diphenylphosphanyl)oxy)ethyl)}amino]butyldiphenylphosphinite, 1 and (2R)-2-[benzyl{(2-((dicyclohexylphosphanyl)oxy)ethyl)}amino]butyldicyclohexylphosphinite, 2 and the corresponding ruthenium(II) complexes 3 and 4 have been prepared. The structures of these complexes have been elucidated by a combination of multinuclear NMR spectroscopy, IR spectroscopy and elemental analysis. P-31-{H-1} NMR, DEPT, H-1-C-13 HETCOR or H-1-H-1 COSY correlation experiments were used to confirm the spectral assignments. These ruthenium(II) ephosphinite complexes have been used as catalysts for the asymmetric transfer hydrogenation of acetophenone derivatives. Under optimized conditions, aromatic ketones were reduced in good conversions and in moderate to good enantioselectivities (up to 85% ee). (C) 2011 Elsevier B. V. All rights reserved.Öğe Bis(phosphinite) with C2-Symmetric Axis; Effects on the Ruthenium(II)-Catalyzed Asymmetric Transfer Hydrogenation of Acetophenone Derivatives(Georg Thieme Verlag Kg, 2012) Aydemir, Murat; Durap, Feyyaz; Kayan, Cezmi; Baysal, Akin; Turgut, YilmazChiral ruthenium catalyst systems generated in situ from [Ru(eta(6)-p-cymene)(mu-Cl)Cl](2) complex and chiral C-2-symmetric bis(phosphinite) ligands based on amino alcohol derivatives were employed in the asymmetric transfer hydrogenation of aromatic ketones to give the corresponding optically active alcohols in high yield. The best results were obtained in the [Ru(eta(6)-p-cymene)(mu-Cl)Cl](2) and (2S)-2-[benzyl(2-{benzyl[(2S)-1-[(diphenylphosphanyl)oxy]-3-phenyl propan-2-yl]amino}ethyl)amino]-3-phenylpropyl diphenylphosphinite or (2R)-2-[benzyl(2-{benzyl[(2R)-1-[(diphenylphosphanyl) oxy]-3-phenylpropan-2-yl]amino}ethyl) amino]-3-phenylpropyl diphenylphosphinite catalytic systems, which gave enantioselectivities of up to 93% ee and 99% conversion.Öğe Chiral separation of amino acids using a chiral crown ether by impregnation on a polymeric support and monoamine modified silica gel(Pergamon-Elsevier Science Ltd, 2006) Seyhan, Serap; Turgut, Yilmaz; Merdivan, Melek; Hosgoren, HalilA chiral monoaza-15-crown-5 ether derivative was prepared from L-Leucinol and used as a chiral stationary phase. The new chiral stationary phases CSP-1 and CSP-2 were employed in separating the enantiomers of the sodium and potassium salts of amino acids. The sodium and potassium salt of the D-enantiomers of all amino acids (PhyAlaNa, PhyAlaK and PhyGlyNa, PhyGlyK, and TrpNa, TrpK) show higher selectivity than the L-enantiomers for both CSP-1 and CSP-2. (c) 2006 Elsevier Ltd. All rights reserved.Öğe Enantiomeric discrimination of chiral organic salts by chiral aza-15-crown-5 ether with C1 symmetry: experimental and theoretical approaches(Springer, 2015) Kocakaya, Safak Ozhan; Turgut, Yilmaz; Pirinccioglu, NecmettinThe work involves an experimental (H-1 NMR) and theoretical (MD, MM-PBSA and DFT) investigation of the molecular recognition and discrimination properties of a chiral aza-15-crown-5 against methyl esters of alanine, phenylalanine and valine hydrochloride salts. The results indicate that the receptor binds enantiomers with moderate binding constants (88-1,389 M-1), with phenylalanine being more discriminated. The difference in experimental binding free energies (Delta G(R) - Delta G(S)) for alanine, phenylalanine and valine enantiomers were calculated as -0.36, -1.58 and 0.80 kcal mol(-1), respectively. The differences in theoretical binding energies were calculated by MM-PBSA (Delta E-PB(R) - Delta E-PB(S)=) as -0.30, -1.45 and 0.88, by B3LYP/6-31+G(d) as -1.17, -0.84 and 0.74 and by M06-2X/6-31+G(d) as -1.40, -3.26 and 1.66 kcal mol(-1). The data obtained give valuable information regarding the molecular recognition mode of the organoammonium complexes of chiral aza-crown ether with C-1 symmetry, which may be relevant to biological systems.Öğe Enantiomeric recognition of amino acid ester salts by ?-cyclodextrin derivatives: an experimental and computational study(Arkat Usa Inc, 2016) Rezanka, Michal; Stibor, Ivan; Azizoglu, Murat; Turgut, Yilmaz; Pirinccioglu, Necmettinbeta-cyclodextrin derivatives bearing benzoyl (beta-CD-1) and naphthoyl beta-CD-2) moieties have been synthesized from salicylic acid and 3-hydroxy-2-naphthoic acid by a convenient method in 60% and 58% yields, respectively, and were tested for enantiomeric recognition of amino acid ester derivatives. Their ability to discriminate between various L-/D-amino acid methyl ester hydrochloride salts was examined using the H-1 NMR titration method in DMSO-d(6) at 25 degrees C. beta-CD- 2 produced a fairly good discrimination of tryptophan ester salts with a binding constant of 4041 M-1 for L-salt compared with 2864 M-1 for D-salt, which corresponds to a difference of 0.21 kcal mol(-1) in binding free energies. The binding free energies obtained from molecular dynamic calculation by MM/PB(GB) SA are consistent with those obtained from the experimental results.Öğe ?-Hydroxyamide derivatives of salicylic acid as organocatalysts for enantioselective reductions of prochiral ketones(Pergamon-Elsevier Science Ltd, 2013) Turgut, Yilmaz; Azizoglu, Murat; Erdogan, Asli; Arslan, Nevin; Hosgoren, HalilIn order to find the most effective catalyst for the enantioselective reduction of a prochiral ketone, a series of novel beta-hydroxyamide derivatives of salicylic acid and chiral amino alcohols were synthesized. Different substituted prochiral ketones have been reduced in high yield (up to 99%) and the corresponding secondary alcohols are formed with good enantiomeric excess (up to 86%). The mechanism of this type of catalyst can be explained by considering the reaction mechanism for the CBS catalyst. (C) 2013 Elsevier Ltd. All rights reserved.Öğe Microwave-assisted synthesis of novel amide based chiral tripodal receptors for recognition of cation and anion sensors(Arkat Usa Inc, 2016) Azizoglu, Sevil S.; Kaplan, Seref; Ozturk, Gulsen; Turgut, Yilmaz; Togrul, MahmutFive novel amide based chiral tripodal receptors were synthesized under microwave irradiation by reacting nitrilotriacetic acid with chiral amino alcohols in a solvent-free medium with high yields (>= 90%). The recognition affinities of these tripodal receptors were investigated towards anions and chiral organic ammonium cations using H-1 NMR titration method. The results show that receptor 1 displays more affinity against anions compared with other receptors and the tripodal receptor 4 demonstrated a significant enantiomeric selectivity towards the (R)-naphthylethylammonium perchlorate (ERF 54%).Öğe A modular design of ruthenium(II) catalysts with chiral C2-symmetric phosphinite ligands for effective asymmetric transfer hydrogenation of aromatic ketones(Pergamon-Elsevier Science Ltd, 2010) Aydemir, Murat; Meric, Nermin; Baysal, Akin; Gumgum, Bahattin; Togrul, Mahmut; Turgut, YilmazHydrogen-transfer reduction processes are attracting increasing interest from synthetic chemists in view of their operational simplicity. The new chiral C-2-symmetric ligands N,N'-bis-[(1S)-1-sec-butyl-2-O-(diphenylphosphinite)ethyl]ethanediamide, 1 and N,N'-bis-[(1S)-1-phenyl-2-O-(diphenylphosphinite)ethyl]ethanediamide, 2 and the corresponding ruthenium complexes 3 and 4 have been prepared and their structures have been elucidated by a combination of multi-nuclear NMR spectroscopy, IR spectroscopy, and elemental analysis. H-1-P-31 NMR, DEPT, H-1-C-13 HETCOR, or H-1-H-1 COSY correlation experiments were used to confirm the spectral assignments. The catalytic activity of complexes 3 and 4 in transfer hydrogenation of acetophenone derivatives by iso-PrOH has also been studied. Under optimized conditions, these chiral ruthenium complexes serve as catalyst precursors for the asymmetric transfer hydrogenation of acetophenone derivatives in iso-PrOH and act as excellent catalysts, giving the corresponding chiral alcohols in 99% yield and up to 75% ee. This transfer hydrogenation is characterized by low reversibility under these conditions. (C) 2010 Elsevier Ltd. All rights reserved.Öğe New C2-symmetric chiral phosphinite ligands based on amino alcohol scaffolds and their use in the ruthenium-catalysed asymmetric transfer hydrogenation of aromatic ketones(Elsevier France-Editions Scientifiques Medicales Elsevier, 2013) Durap, Feyyaz; Aydemir, Murat; Elma, Duygu; Baysal, Akin; Turgut, YilmazAsymmetric transfer hydrogenation processes of ketones with chiral molecular catalysts are attracting increasing interest from synthetic chemists due to their operational simplicity. C-2-symmetric catalysts have also received much attention and been used in many reactions. A series of new chiral C-2-symmetric bis(phosphinite) ligands has been prepared from corresponding amino acid derivated amino alcohols or (R)-2-amino-1-butanol through a three- or four-step procedure. Their structures have been elucidated by a combination of multinuclear NMR spectroscopy, IR spectroscopy and elemental analysis. H-1-P-31 NMR, DEPT, H-1-C-13 HETCOR or H-1-H-1 COSY correlation experiments were used to confirm the spectral assignments. In situ prepared ruthenium catalytic systems were successfully applied to ruthenium-catalyzed asymmetric transfer hydrogenation of acetophenone derivatives by iso-PrOH. Under optimized conditions, these chiral ruthenium catalyst systems serve as catalyst precursors for the asymmetric transfer hydrogenation of acetophenone derivatives in iso-PrOH and act as good catalysts, giving the corresponding optical secondary alcohols in 99% yield and up to 79% ee. (C) 2012 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.Öğe A new efficient bis(phosphinite)-ruthenium(II) catalyst system for the asymmetric transfer hydrogenation of aromatic ketones(Elsevier Science Sa, 2014) Durap, Feyyaz; Aydemir, Murat; Baysal, Akin; Elma, Duygu; Ak, Bunyamin; Turgut, YilmazMany chiral ligands bearing phosphorus donor atoms were developed and applied in the area of metal catalyzed asymmetric catalysis. A new chiral bis(phoshinite) ligand was successfully synthesized from optically active (1S,8S)-3,6-[N-(S)-alpha-phenylethyl] diaza-1,8-diphenoxymethyl-1,8-octanediol in high yield. A ruthenium(II) complex generated in situ from [Ru(eta(6)-p-cymene)(mu-Cl)Cl](2), bis(phosphinite) ligand and KOH acts as an active catalyst for asymmetric transfer hydrogenation (ATH) of acetophenone derivatives in isopropyl alcohol (IPA) as both solvent and hydrogen source. The catalytic reaction proceeds cleanly to give enantiomerically enriched secondary alcohols up to 90% or 89% ee's at 50 or 82 degrees C, respectively. (C) 2013 Elsevier B. V. All rights reserved.Öğe Pyridine containing chiral macrocycles: synthesis and their enantiomeric recognition for amino acid derivatives(Pergamon-Elsevier Science Ltd, 2011) Deniz, Pinar; Turgut, Yilmaz; Togrul, Mahmut; Hosgoren, HalilFour novel C(2)-symmetric enantiomerically pure, chiral pyridine-18-crown-6 type macrocycles containing lipophilic chains at the stereogenic centers were prepared. The enantioselectivity of the new ligands toward the enantiomers of D-,L-amino acid methyl ester derivatives were also determined by (1)H NMR titration method. These novel macrocycles have been showed to be strong complexing agents for D- and L-amino acid methyl ester hydrochloride salts (with K(ass) up to 13590 M(-1) and Delta G(0) up to 23.3 kJ mol(-1) and selectivity ratio: 80:20) by (1)H NMR titration methods. These macrocyclic hosts exhibited enantioselective binding towards the D-enantiomer of valine methyl ester hydrochloride with K(D)/K(L), up to 5.08 in CDCl(3) with 0.25% CD(3)OD. (C) 2011 Elsevier Ltd. All rights reserved.Öğe Pyridine-containing chiral macrocycles for the enantioselective recognition of amino acid derivatives and their molecular dynamics simulations(Pergamon-Elsevier Science Ltd, 2010) Turgut, Yilmaz; Kocakaya, Safak OzhanTwo novel C-2-symmetric optically active pyridine-15-crown-5 type ligands containing lipophilic chains at the stereogenic centres, macrocycles 5 and 6, were prepared from (S)-1,2-propanediol and (S)-3-aryloxy-1,2-propanediol for the enantiomeric recognition of amino acid ester derivatives. These novel macrocycles have been shown to be strong complexing agents for primary organic ammonium salts (with K values of up to 1363.5 M-1, Delta G degrees of up to 17.86 kJ mol(-1) and a selectivity ratio of 80:20) by H-1 NMR titration method. These macrocyclic host exhibited enantioselective binding towards the L-enantiomer of phenylalanine methyl ester hydrochloride with K-L/K-D up to 8.57 in CDCl3 containing 0.25% CD3OD. Experimental results have been detailed with molecular dynamic calculations at atomic level concerning the molecular recognition and discrimination properties of a chiral pyridino-15-crown-5. The binding free energies were calculated as similar to-25 kJ mol(-1). The results indicated that the host binds and discriminates valine salts better than phenylalanine salts. The molecular dynamics, MM/PBSA calculations are consistent with the H-1 NMR results. (C) 2010 Elsevier Ltd. All rights reserved.Öğe Screening of C2-symmetric chiral phosphinites as ligands for ruthenium(II)-catalyzed asymmetric transfer hydrogenation of prochiral aromatic ketones(Elsevier Science Sa, 2013) Elma, Duygu; Durap, Feyyaz; Aydemir, Murat; Baysal, Akin; Meric, Nermin; Ak, Bunyamin; Turgut, YilmazMetal-catalyzed transfer hydrogenation processes provide a widely-used alternative to direct hydrogenation processes of ketones. As part of an ongoing program, we report enantioselective C-2-symmetric bis(phosphinite)-ruthenium(II) catalytic systems for the transfer hydrogenation of prochiral aromatic ketones. The new catalytic systems can readily be formed under in situ conditions from C-2-symmetric chiral bis(phosphinite) ligands and [Ru(eta(6)-p-cymene)(mu-Cl)Cl](2) in transfer hydrogenation reaction media. These chiral ruthenium catalytic systems serve as catalyst precursors for the asymmetric transfer hydrogenation of acetophenone derivatives in iso-PrOH and giving the corresponding optical active secondary alcohols up to 94% ee. (C) 2013 Elsevier B.V. All rights reserved.Öğe A series of novel ?-hydroxyamide based catalysts for borane-mediated enantioselective reductions of prochiral ketones(Pergamon-Elsevier Science Ltd, 2016) Azizoglu, Murat; Erdogan, Asli; Arslan, Nevin; Turgut, Yilmaz; Hosgoren, Halil; Pirinccioglu, NecmettinThe enantioselective reduction of prochiral ketones with borane in the presence of a chiral ligand has received considerable attention. Hydroxylamine-based chiral ligands with amide and hydroxyl functions in the presence of other co-ordinating groups are highly effective in these asymmetric reductions. The current work presents a simple one step synthesis of a series of beta-hydroxyamide-based ligands from the reaction between 3-hydroxy-2-naphthoic acid and chiral amino alcohols and their applications as catalysts in asymmetric borane-mediated reductions of aromatic prochiral ketones in THE The reductions provided the corresponding secondary alcohols with up to 96% ee and in good to excellent yields (89-99%). OFF calculations at B3LYP/6-31+g(d) level offered theoretical models to account for the enantioselectivity imposed by the chiral ligands in the reductions of the ketones. (C) 2016 Elsevier Ltd. All rights reserved.Öğe The synthesis and formation of complexes between derivatives of chiral Aza-18-crown-6 ethers and chiral primary organic ammonium salts(Springer, 2006) Karakaplan, Mehmet; Turgut, Yilmaz; Aral, Tarik; Hosgoren, HalilChiral mono aza-18-crown-6 derivatives have been prepared in optically active form and high yield from amino alcohols via a cyclization reaction with tetraethylene glycol ditosylate. The enantiomeric recognition by these chiral aza-crown ethers between chiral primary ammonium perchlorate salts has been characterized by UV-Vis at 25 degrees C in chloroform.Öğe Synthesis of C2-Symmetric Chiral Amino Alcohols: Their Usage as Organocatalysts for Enantioselective Opening of Epoxide Ring(Taylor & Francis Inc, 2010) Turgut, Yilmaz; Aral, Tarik; Karakaplan, Mehmet; Deniz, Pinar; Hosgoren, HalilA series of -amino alcohols derivatives were synthesized from (R)-2-amino-1-butanol and (S)-1,2-propanediol, and they have been used as organocatalaysts in the racemic ring opening of epoxide in good yields with high enantiomeric excess (up to 97%).Öğe Synthesis of novel C2-symmetric chiral crown ethers and investigation of their enantiomeric recognition properties(Pergamon-Elsevier Science Ltd, 2009) Turgut, Yilmaz; Aral, Tarik; Hosgoren, HalilA series of new C-2-symmetric chiral aza crown ether macrocycles 1-4 have been synthesized from (S)-3-aryloxy-1,2-propanediol and (S)-1,2-propanediol for the enantiomeric recognition of amino acid ester derivatives. These new macrocycles have been shown to be strong complexing agents for primary organic ammonium salts (with K up to 176.93 M-1 and Delta G degrees up to 12.81 kJ mol(-1)) by H-1 NMR titration. These macrocyclic host exhibited enantioselective bonding toward the D-enantiomer of phenylalanine methyl ester hydrochloride with K-D/K-L up to 6.87 in CDCl3 with 0.25% CD3OD. (C) 2009 Elsevier Ltd. All rights reserved.Öğe Synthesis of rigid and C2-symmetric pyridino-15-crown-5 type macrocycles bearing diamide-diester functions: enantiomeric recognition for chiral primary organoammonium perchlorate salts(Pergamon-Elsevier Science Ltd, 2014) Seker, Sevil; Baris, Deniz; Arslan, Nevin; Turgut, Yilmaz; Pirinccioglu, Necmettin; Togrul, MahmutFour novel C-2-symmetric macrocyclic compounds with a pyridine function and possessing amide and ester lingeages were prepared. The enantiomeric discrimination abilities of these macrocycles against alpha-phenylethylammonium and alpha-(1-naphthyl)ethylammonium perchlorate salts were measured by standard H-1 NMR titration techniques in DMSO-d(6). A binding constant ratio of 31 (Kbind(S)/Kbind(R)) for two enantiomers of alpha-(1-naphthyl)ethylammonium salt with the macrocyclic host (S,S)-4 bearing phenyl arms was observed, which corresponds to an enantiomeric discrimination of approximately 94%. Molecular dynamic calculations were performed for some of the supramolecular complexes to in order to gain insight into the mode of molecular recognition between the macrocyclic compounds and ammonium salts; these results were consistent with experimental observations, which may be relevant to those in biochemical processes occurring in organisms. (C) 2014 Elsevier Ltd. All rights reserved.
