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Active ruthenium-(N-heterocyclic carbene) complexes for hydrogenation of ketones
(Wiley-Blackwell, 2006) Yigit, Murat; Yigit, Beyhan; Ozdemir, Ismail; Cetinkaya, Engin; Cetinkaya, Bekir
Four ruthenium-N-heterocyclic carbene complexes (3-6) have been prepared and the new compounds characterized by C, H, N analyses, H-1-NMR and C-13-NMR. The reduction of ketones to alcohols via transfer hydrogenation was achieved with catalytic amounts of complexes 3-6 in the presence of t-BuOK. Copyright (c) 2006 John Wiley & Sons, Ltd.
Conversion of carbon dioxide to cyclic carbonates using diimine Ru(II) complexes as catalysts
(John Wiley & Sons Ltd, 2009) Ulusoy, Mahmut; Cetinkaya, Engin; Cetinkaya, Bekir
Cationic diimine Ru(II) complexes were synthesized and tested as catalysts for the formation of cyclic organic carbonates from CO(2) and liquid epoxides (propylene oxide, epichlorohydrine, 1,2-epoxybutane and styrene oxide) which served as both reactant and solvent. The reaction rates not only depended on the type of ligand, but also on reaction conditions such as temperature, pressure, base, the epoxide substrates and the use of an additional solvent. Reaction rates in terms of turnover frequencies up to 4050 molproduct mol(product) mol(cat.)(-1) h(-1) at 99% selectivity were achieved by optimizing the diimine ligand as well as the reaction temperature and CO(2) pressure. Consistent with CV measurements, the electron donating group on the p-position of the aryl ring accelerated the reaction rate. Copyright (c) 2008 John Wiley & Sons, Ltd.
In situ catalytic activities of 1,3-dialkyltetrahydropyrimidinium salts/[RuCl2(p-cymene)](2) system for transfer hydrogenation reactions
(Scientific Technical Research Council Turkey-Tubitak, 2011) Ozcan, Emine Ozge; Mercan, Deniz; Gurbuz, Nevin; Cetinkaya, Engin; Cetinkaya, Bekir; Ozdemir, Ismail
Hydrogen-transfer reduction processes are attracting increasing interest from synthetic chemists in view of their operational simplicity. In the present study novel ruthenium carbene complexes were generated in situ and tested for their transfer hydrogenation reactions. The in situ prepared 3 component 1,3-dialkyltetrahydropyrimidinium salts (LHX)/[RuCl2(p-cymene)](2) and KOH catalyzed quantitatively the transfer hydrogenation of ketones under mild reaction conditions in 2-propanol.
Influence of CH3 substituents on tetrahydropyrimidin-2-ylidene: sigma-donating properties and in situ catalytic activities of precursor salts/Pd(OAc)(2) system for C-C coupling reactions
(Elsevier Science Sa, 2011) Mercan, Deniz; Cetinkaya, Engin; Cetinkaya, Bekir
In this study, symmetrical and non-symmetrical 1,3-dialkyltetrahydropyrimidinium salts (1 center dot HCl and 2 center dot HBr, respectively), bearing two methyl groups at C-5 position of the pyrimidine ring were synthesized and characterized. One of the new salts 1,3-bis(2,4,6-trimethylbenzyl)-5,5-dimethyl-3,4,5,6-tetrahydropyrimidinium tetrafluoroborate (1a center dot HBF4, 1a = 6-Bn*-Me-2) was converted to cis-[RhCl(6-Bn*-Me-2)(CO)(2)] to determine the sigma-donating properties in comparison to those of their 5-membered NHC complexes. Furthermore, the in situ catalytic activities of all salts, in combination with Pd(OAc)(2), were tested for the HeckeMizoraki and SuzukieMiyaura type C-C coupling reactions. In contrast to the expectation, only the substituents on N,N'-atoms were found to play an important role in the catalytic activity. (C) 2011 Elsevier B.V. All rights reserved.
Ionic liquids as solvents/catalysts for selective alkylation of amines with alkyl halides
(Science China Press, 2007) Gok, Yetkin; Ozdemir, Ismail; Cetinkaya, Engin
The selective alkylation of amino groups within amine derivatives with a variety of alkyl halides was carried out using ionic liquids ([bmim] I and [bmim] PF6) in the presence of triethylamine. The reaction was found to proceed under relatively mild conditions with excellent conversions and selectivities. The ionic liquid was recycled and reused.
Microwave-Assisted Synthesis of Novel Perimidinium Salts as N-Heterocyclic Carbene Precursors: Involvement in Palladium-Catalyzed Cross-Coupling Reactions
(Springer, 2015) Onar, Gulnihan; Karatas, Mert Olgun; Alici, Bulent; Cetinkaya, Engin
In the current study, five novel perimidinium chlorides were synthesized in good yields by reaction of 1-(3-methylbenzyl)perimidine with five different alkyl chlorides under microwave irradiation in 30 minutes. Synthesized compounds were characterized by IR, H-1, C-13 NMR spectroscopic methods and elemental analyses. Performance of in situ formed catalytic system which consist of the perimidinium salts and Pd(OAc)(2) was investigated for Heck and Suzuki reactions in aqueous media, and desired products were obtained in good yields.
Microwave-Assisted Synthesis of Novel Perimidinium Salts as N-Heterocyclic Carbene Precursors: Involvement in Palladium-Catalyzed Cross-Coupling Reactions
(Springer, 2015) Onar, Gulnihan; Karatas, Mert Olgun; Alici, Bulent; Cetinkaya, Engin
In the current study, five novel perimidinium chlorides were synthesized in good yields by reaction of 1-(3-methylbenzyl)perimidine with five different alkyl chlorides under microwave irradiation in 30 minutes. Synthesized compounds were characterized by IR, H-1, C-13 NMR spectroscopic methods and elemental analyses. Performance of in situ formed catalytic system which consist of the perimidinium salts and Pd(OAc)(2) was investigated for Heck and Suzuki reactions in aqueous media, and desired products were obtained in good yields.
Microwave-Assisted Synthesis of Novel Perimidinium Salts as N-Heterocyclic Carbene Precursors: Involvement in Palladium-Catalyzed Cross-Coupling Reactions
(Springer, 2015) Onar, Gulnihan; Karatas, Mert Olgun; Alici, Bulent; Cetinkaya, Engin
In the current study, five novel perimidinium chlorides were synthesized in good yields by reaction of 1-(3-methylbenzyl)perimidine with five different alkyl chlorides under microwave irradiation in 30 minutes. Synthesized compounds were characterized by IR, H-1, C-13 NMR spectroscopic methods and elemental analyses. Performance of in situ formed catalytic system which consist of the perimidinium salts and Pd(OAc)(2) was investigated for Heck and Suzuki reactions in aqueous media, and desired products were obtained in good yields.
New coumarin derivatives as carbonic anhydrase inhibitors
(Taylor & Francis Ltd, 2014) Karatas, Mert Olgun; Alici, Bulent; Cakir, Umit; Cetinkaya, Engin; Demir, Dudu; Ergun, Adem; Gencer, Nahit; Arslan, Oktay
In the current study, a series of 4-chloromethyl-7-hydroxy-coumarin derivatives containing imidazolium, benzimidazolium, bisbenzimidazolium and quaternary ammonium salts were synthesized, characterized and the inhibition effects of the derivatives on human carbonic anhydrases (hCA I and hCA II) were investigated as in vitro. Structures of these coumarins were confirmed by FT-IR, (1)H NMR, (13)C NMR and LC-MS analyses. Structure activity relationship study showed that 3d (IC50: 79 mu m M for hCA I and 88 m M for hCA II) performed higher inhibitory activity than others.
Novel azolinium/rhodium system catalyzed addition of arylboronic acids to aldehydes
(Pergamon-Elsevier Science Ltd, 2006) Ozdemir, Ismail; Yigit, Murat; Cetinkaya, Engin; Cetinkaya, Bekir
There novel 1,3-dialkylperhydrobenzimidazolinium (2a-c) and two 1,3-dialkylimidazolinium salts (4a,b) as NHC precursors were synthesized from N,N'-dialkyl-1,2-cyclohexanediamine dihydrochloride and 1,2-dialkylpropanediamine dihydrochloride. The in situ prepared three component system [RhCl(COD)](2)/imidazolinium salts (2, 4) and KOBut catalyses the addition of phenylboronic acid to sterically hindered aldehydes affording the corresponding arylated secondary alcohols in good yields.
Novel rhodium N-heterocyclic carbene catalysed arylation of aldehydes with phenylboronic acid
(Springer, 2007) Yigit, Murat; Ozdemir, Ismail; Cetinkaya, Engin; Cetinkaya, Bekir
Reaction of 1,3-dialkylperhydrobenzimidazolinylidene, 1,3-dialkyl-4-methylimidazolinylidene and 1,3-dialkylimidazolinylidene with [RhCl(COD)](2) yields {1,3-dialkylperhydrobenzimidazolin- 2-ylidene}-, {1,3-dialkyl-4-methylimidazolin- 2-ylidene}- {1,3-dialkylimidazolin-2-ylidene} chloro(eta(4)- 1,5- cyclooctadiene) rhodium(I) complexes (2a-c) and ( 4a, b). All compounds synthesised were characterised by elemental analysis, n.m.r. spectroscopy. Phenylboronic acid reacts with aldehydes in the presence of a catalytic amount of the new rhodium(I)-carbene complexes (2a-c) and (4a, b), to give the corresponding aryl secondary alcohols in good yield (73-99%).
Perimidin-2-ylidene rhodium(I) complexes; unexpected halogen exchange and catalytic activities in transfer hydrogenation reaction
(Elsevier Science Sa, 2014) Akinci, P. Arzu; Gulcemal, Suleyman; Kazheva, Olga N.; Alexandrov, Grigorii G.; Dyachenko, Oleg A.; Cetinkaya, Engin; Cetinkaya, Bekir
Four new [(NHC)RhCl(COD)] (NHC = perimidin-2-ylidene; COD = 1,5-cyclooctadiene) rhodium complexes (4a-c and 5a) have been prepared by the reaction of [Rh(mu-OMe)(COD)](2) with perimidinium bromides (2a-c and 3a). The halogen exchange, abstracted from 1,2-dichloroethane was observed during the reaction and [(NHC)RhCl(COD)] complexes were obtained instead of [(NHC)RhBr(COD)]. All ligand precursors and complexes have been fully characterized by H-1, C-13 NMR, IR spectroscopy, elemental analysis and mass spectroscopy. X-ray diffraction studies on single crystals of 4a and 5a confirm the square planar geometry. The nu((CO)) values of [(NHC)RhCl(CO)(2)] complexes (6a-c and 7a) revealed that the NHC ligands are not good sigma-donors. Transfer hydrogenation (TH) reaction of aliphatic and aromatic ketones has been comparatively studied by using complexes 4a-c and 5a as catalysts. (C) 2014 Elsevier B.V. All rights reserved.
Ru(II)-arene complexes with N-substituted 3,4-dihydroquinazoline ligands and catalytic activity for transfer hydrogenation reaction
(Elsevier Science Sa, 2013) Mercan, Deniz; Cetinkaya, Engin; Sahin, Ertan
In this study, N-coordinated 3,4-dihydroquinazoline ruthenium(II) complexes were synthesized by the cleavage reaction of [RuCl2(p-cymene)](2) wit h N-substituted 3,4-dihydroquinazolines. In addition, the X-ray crystal structure of 2,4,6-trimethylbenzyl substituted 3,4-dihydroquinazoline Ru(II) complex (1a) is reported. Furthermore, the resulting piano-stool complexes were evaluated as transfer hydrogenation catalysts for reduction of acetophenone in the presence of 2-propanol and KOH at 82 degrees C. All the complexes showed good to excellent performance after 1 h in the conversion of acetophenone to alcohol and the reaction rate was found to be sensitive to changes on the N-substituent. Additionally, the most active catalyst 1a was used in trans fer hydrogenation of different ketones to investigate the effect of substituents on ketones. (C) 2013 Elsevier B.V. All rights reserved.
Selenourea and thiourea derivatives of chiral and achiral enetetramines: Synthesis, characterization and enzyme inhibitory properties
(Academic Press Inc Elsevier Science, 2022) Yigit, Murat; Celepci, Duygu Barut; Taslimi, Parham; Yigit, Beyhan; Cetinkaya, Engin; Ozdemir, Ismail; Aygun, Muhittin
A series of chiral and achiral cyclic seleno-and thiourea compounds bearing benzyl groups on N-atoms were prepared from enetetramines and appropriate Group VI elements in good yields. All the synthesized compounds were characterized by elemental analysis, FT-IR, H-1 NMR and C-13 NMR spectroscopy, and the molecular and crystal structures of (R,R)-4b and (R,R)-5b were confirmed by the single-crystal X-ray diffraction method. These assayed for their activities against metabolic enzymes acetylcholinesterase, butyrylcholinesterase, and alpha-glycosidase. These selenourea and thiourea derivatives of chiral and achiral enetetramines effectively inhibit AChE and BChE with IC50 values in the range of 3.32-11.36 and 1.47-9.73 mu M, respectively. Also, these compounds inhibited alpha-glycosidase enzyme with IC50 values varying between 1.37 and 8.53 mu M. The results indicated that all the synthesized compounds exhibited excellent inhibitory activities against mentioned enzymes as compared with standard inhibitors. Representatively, the most potent compound against alpha-glycosidase enzyme, (S,S)-5b, was 12-times more potent than standard inhibitor acarbose; 7b and 8a as most potent compounds against cholinesterase enzymes, were around 5 and 13-times more potent than standard inhibitor tacrine against achethylcholinesterase (AChE) and butyrylcholinesterase (BChE), respectively.
Synthesis and antimicrobial properties of cycloheptyl substituted benzimidazolium salts and their silver(I) carbene complexes
(Walter De Gruyter Gmbh, 2016) Karatas, Mert Olgun; Gunal, Selami; Mansur, Ahmet; Alici, Bulent; Cetinkaya, Engin
Due to increasing infections caused by microbes, there is an urgent need for the development of new effective antimicrobial agents. Silver-N-heterocyclic carbene (silver-NHC) complexes are a new class of antimicrobial agents. In this study, we aimed to synthesize highly lipophilic silver-NHC complexes. Four new complexes were synthesized by the reaction of the corresponding benzimidazolium salts and Ag2O in dichloromethane at room temperature. The synthesized compounds were characterized by H-1 NMR, C-13 NMR, IR and elemental analysis. The antimicrobial performances of benzimidazolium salts and silver complexes were tested against the standard bacterial strains Enterococcus faecalis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and the fungi Candida albicans and Candida tropicalis. Minimum inhibitory concentrations (MICs) of all compounds were determined. The obtained data demonstrate that all benzimidazolium salts and silver complexes inhibit the growth of bacteria and fungi. Silver complexes are more active than the corresponding benzimidazolium salts (MIC: 6.25 mu g/mL for Gram-positive bacteria and fungi).
Synthesis and carbonic anhydrase inhibitory properties of novel coumarin derivatives
(Informa Healthcare, 2013) Karatas, Mert Olgun; Alici, Bulent; Cakir, Umit; Cetinkaya, Engin; Demir, Dudu; Ergun, Adem; Gencer, Nahit; Arslan, Oktay
A newly series of water-soluble 1-alkyl-3-(4-methyl-7, 8-dihydroxy-2H-chromen-2-one) benzimidazolium chloride salts (3a-j) were synthesized and their inhibitory effects on the activity of purified human carbonic anhydrase (hCA) I and II were evaluated. hCA I and II from human erythrocytes were purified by a simple one step procedure by using Sepharose 4B-L-tyrosine-sulphanilamide affinity column. The result showed that all the synthesized compounds were inhibited the CA isoenzymes activity. Among them, 3g and 3j were found to be most active (IC50 = 22.09 mu M and 20.33 mu M) for hCA I and hCA II, respectively.
Synthesis and catalytic properties of N-functionalised carbene complexes of rhodium(I)
(Taylor & Francis Ltd, 2007) Oezdemir, Ismail; Yigit, Murat; Yigit, Beyhan; Cetinkaya, Bekir; Cetinkaya, Engin
Reaction of [RhCl(COD)] 2, with 1,3-dialkylimidazolinylidene (1) or 1,3-dialkylbenzimidazolinylidene (2) resulted in the formation of rhodium(I) 1,3-dialkylimidazolin-2-ylidene (3a-c) and 1,3-dialkylbenzimidazolin-2-ylidene (4a, b) complexes. Triethylsilane reacts with acetophenone derivatives in the presence of catalytic amounts of RhCl(COD)(1,3-dialkylimidazolin-2-ylidene) or RhCl(COD)(1,3-dialkylbenzimidazolin-2-ylidene) to give the corresponding silylethers in good yield (57-98%).
Synthesis and characterization of polyimides prepared from optically active (R,R) and (S,S)-1,3-bis(p-N,N '-dimethylaminobenzyl)-perhydrobenzimidazol-2-thion
(Scientific Technical Research Council Turkey-Tubitak, 2007) Yigit, Murat; Seckin, Turgay; Koytepe, Suleyman; Cetinkaya, Engin
This paper presents the synthesis and characterization of polyimides containing a chiral (R, R) or (S,S) 1,3-bis(p - N,N'-dimetylaminobenzyl)-perhydrobenzimidazol-2-thion unit in the backbone. The reactions occur betweem equimolar amounts of a dianhydride and all aromatic dimethylamine. in the presence of the solvent N-methyl-2-pyrollidone (NMP). In this work, the chiral monomer RR and SS -1,3-bis(p - N,N'-dimethylaminobenzyl)-perhydrobenzimidazol-2-thion were used as diamines. The polyimides obtained were characterized bu thermogravimetry (TGA), differential thermal analysis (DTA), differential scanning calorimeter (DSC), infrared spectroscopy (FT-IR) and gel permeation chromatography (GPC). It was found that the composition of the polymer had a significant effect upon the thermal behavior of the material.
Synthesis and use of mono- or bisxylyl linked bis(benzimidazolium) bromides as carbene precursors for C-C bond formation reactions
(Elsevier Science Sa, 2008) Tuerkmen, Hayati; Denizalti, Serpil; Oezdemir, Ismail; Cetinkaya, Engin; Centinkaya, Bekir
Two benzimidazolium moieties linked by one or two xylyls (m- and p-) have been synthesized, characterized and then they were used for Heck coupling reactions as in situ formed catalysts. Mono bridged salts are more efficient as compared to bisbridged salts. In addition, mono bridged salts were converted to Rh-NHC complexes which were tested as catalysts for the arylation of aldehydes. (C) 2007 Elsevier B.V. All rights reserved.
THE SYNTHESIS OF NOVEL PALLADIUM(II) CARBENE COMPLEXES, AZOLIUM SALTS AND THEIR CATALYTIC PROPERTIES
(Pergamon-Elsevier Science Ltd, 2011) Yigit, Beyhan; Yigit, Murat; Ozdemir, Ismail; Cetinkaya, Engin
Novel three 1,3-bis[2-(N,N'-diisopropylamino)ethyl]imidazolinium, 1,3-bis[2-(N,N'-diisopropylamino)ethyl]benzimidazolium and 1-(2-diisopropylaminoethyl)-3-(2-methoxyethyl)benzimidazolium chloride salts (1, 3a-b) and two palladium complex (2, 4) have been prepared and characterized by C, H, N analysis, H-1 NMR and C-13 NMR and they have been investigated their catalytic activity in the Heck and Suzuki coupling reactions.

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