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Phenyl Ring (phenyl + ring)
Selected AbstractsStepwise Delivery of Two Methoxy Groups of Arylaldehyde Acetals Across the Phenyl Ring.CHEMINFORM, Issue 47 2005Vacant Site-Controlled Palladium Catalysis. Abstract For Abstract see ChemInform Abstract in Full Text. [source] Functionalization at Position 3 of the Phenyl Ring of the Potent mGluR5 Noncompetitive Antagonists MPEP.CHEMINFORM, Issue 25 2005David Alagille Abstract For Abstract see ChemInform Abstract in Full Text. [source] Chiral ion-exchange capillary electrochromatography of arylglycine amides with dextran sulfate as a pseudostationary phaseELECTROPHORESIS, Issue 4-5 2005Yi Chen Abstract A low-cost tunable chiral ion-exchange capillary electrochromatographic method has been developed for the separation of arylglycine amide racemic mixtures with dextran sulfate (DS) as an anionic and chiral pseudostationary phase and Tris-tartrate as a buffer system. The concentrations of DS and Tris had opposite influences on retention and resolution and could serve as ideal factors to finely tune the running speed and chiral resolution. Tartrate and pH largely impact the separation but pH should be confined within 3.0,5.5, only suitable for coarse tuning, while tartrate was preserved as the key buffering reagent, normally maintained at 40 mmol/L. With a working system composed of 0.1,1.0% DS, 20,60 mmol/L Tris, and 40 mmol/L tartrate at pH 3.50,4.50, the enantioresolution of arylglycine amides was shown to be dependent on their chemical structure: The chiral resolution increased when the hydrogen at the ,-amino group or at the p -position of phenyl ring was replaced by other larger group(s) but the resolution decreased when the group at the o- or m- site on the phenyl ring was enlarged. Further, the electronegative substitute of -Cl had larger resolution increment than methyl or methoxy at the position p- of phenyl ring but much lower increment at position m- . It is possible to well explain the resolution variation phenomenon by considering the group resistance and the variation of hydrogen-bonds formed inside the amino amides and between the solutes and DS. The amido group was shown irreplaceable to have chiral resolution with DS alone as an ionic and chiral pseudostationary phase. [source] Potential for octylphenol to biodegrade in some english riversENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 10 2000Andrew C. Johnson Abstract To study octylphenol biodegradation, samples of river water and sediments were taken from the Aire and Calderr vers in the United Kingdom, running through urban/industrial areas, as well as the Thames River running through a more rural area. Using laboratory microcosms, half-lives of 7 to 50 d were obtained for the water samples, with most curves fitting a zero-order reaction. The Calder River was sampled at four separate points along a 45-km length, encompassing rural to increasingly urban/industrial reaches. Little degradation was observed in the sample from the upland/rural reach, while half-lives of 8 to 13 d were seen in the more urban/industrial reaches. Mineralization of the phenyl ring, detected by evolution of 14CO2 from ring-labeled octylphenol, was only observed in water from the Calder River sample. Degradation rate was similar for a range of concentrations from 0.3 to 100 ,,g/L when tested with river water from the Thames River. No degradation was observed over 83 d when bed sediments were spiked with octylphenol and incubated under anaerobic conditions. [source] meta -Terphenyl Phosphaalkenes Bearing Electron-Donating and -Accepting GroupsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 6 2010Vittal B. Gudimetla Abstract A set of para -substituted meta -terphenyl phosphaalkenes of the form 4-X-2,6-Mes2C6H2P=C(H)C6H4 -4-X, (X = H, MeO or NMe2; X, = H, CN, or NO2) have been synthesized to allow systematic studies of the impact of remote X and X, substituents on the phosphaalkene unit. The new compounds were characterized by 1H and 31P NMR spectroscopy, UV/Vis absorption spectroscopy, single X-ray crystal structures (for four compounds) and by electrochemical studies. The introduction of remote groups (X,) on the less hindered phenyl ring generated more significant effects on the physical properties of the materials than did substituents (X) on the hindered meta -terphenyl rings. These effects were also explored by computational methods in order to assess the influence of substituents on structures and properties. The polarization of these molecules is less than that produced for analogous alkenes, as the phosphaalkenes bear sterically demanding groups that constrain the systems to adopt conformations that are less than ideal for maximum ,-conjugation of the central , network [source] Two New Iron(II) Spin-Crossover Complexes with N4O2 Coordination Sphere and Spin Transition around Room TemperatureEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 36 2009Birgit Weber Abstract The reaction of iron(II) acetate with the tetradentate Schiff base like ligand H2L1 {[3,3,]-[4,5-dihydroxy-1,2-phenylenebis(iminomethylidyne)bis(2,4-pentanedion)]} leads to the formation of the complex [FeL1(MeOH)]. Reaction of this complex with pyridine (py) or N,N,-dimethylaminopyridine (dmap) leads to the two N4O2 -coordinated complexes [FeL1(py)2]·py (1) and [FeL1(dmap)2]·MeOH·0.5dmap (2). Both complexes are spin-crossover compounds that were characterised by using magnetic measurements, X-ray crystallography and temperature-dependent 1H NMR spectroscopy. Special attention was given to the role of the two hydroxy groups on the phenyl ring in the formation of a hydrogen-bonding network and the influence of this network on the spin-transition properties. Although only a gradual spin crossover was observed for both complexes, the transition temperature was shifted to higher temperatures relative to that of the complexes with no additional hydroxy groups at the Schiff base like ligand. The hydrogen-bonding network was responsible for this effect.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Self-Assembly, Structure and Solution Dynamics of Tetranuclear Zn2+ Hydrazone [2×2] Grid-Type ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2006Mihail Barboiu Abstract We describe the self-assembly processes as well as the structural and physico-chemical properties of [2×2]Zn2+4 grid complexes involving the bis-tridentate ligands 7,12, based on bis(hydrazone)pyrimidine complexation subunits and octahedrally coordinated Zn2+ ions. The NMR spectroscopic data and the X-ray crystal structure results indicate that in solution and in the solid state the complexes 13,18 adopt a very compact arrangement providing stable [2×2] hydrazone-grid arrays. The ,,, stacking between the phenyl ring and the hydrazone units of the perpendicular ligands in the complexes induces a perfect orthogonal arrangement suitable for applications in self-organized metallosupramolecular systems. Zinc complexes provide an opportunity to study the acid,base chemistry without the added effects due to paramagnetism or redox chemistry. The intermediate protonated grids undergo relatively rapid proton exchange on the NMR timescale, the presence of a sharp pyrimidine proton resonance suggesting that there is significant delocalization of the negative charge along the backbone of the ligand. Rotation of the phenyl ring is observed. It involves probably a mechanism in which one of the ligands partially dissociates allowing the initially intercalated phenyl group to rotate, before recoordination of the terminal pyridine. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Orientation- and Temperature-Dependent Rotational Behavior of Imidazole Ligands (L) in ,-[Ru(azpy)2(L)2](PF6)2 ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 4 2003Aldrik H. Velders Abstract The synthesis and characterization of the cis bifunctional coordinated ruthenium(II) complexes ,-[Ru(azpy)2(MeIm)2](PF6)2 (,-MeIm) and ,-[Ru(azpy)2(MeBim)2](PF6)2 (,-MeBim) (azpy = 2-phenylazopyridine, MeIm = 1-methylimidazole and MeBim = 1-methylbenzimidazole) is reported. In ,-MeIm the two MeIm ligands can both freely rotate around the Ru,N axes on the NMR timescale. In ,-MeBim the two MeBim ligands appear restricted in their rotation around the Ru,N axes, which becomes slow on the NMR timescale at low temperatures. In contrast to the analogous complexes ,-[Ru(azpy)2(MeBim)2](PF6)2 and cis -[Ru(bpy)2(MeBim)2](PF6)2, only one atropisomer is observed for the two MeBim ligands in ,-MeBim. The orientation of the MeBim ligands appears to correspond to an HT isomer which is similar to the orientation of the MeBim ligands in the most abundant atropisomer found in the related ,-[Ru(azpy)2(MeBim)2](PF6)2. A stacking interaction between the phenyl ring of one azpy and one MeBim ligand is likely to stabilize the observed atropisomer of ,-MeBim, and is such that the rotation of the phenyl ring of one of the two azpy ligands is restricted. At very low temperatures this rotation, or flipping of the phenyl ring between two identical positions, is in the slow-exchange range on the NMR timescale. (© Wiley-VCH Verlag GmbH & Co KGaA, 69451 Weinheim, Germany, 2003) [source] Regioselectivity in the Addition of Grignard Reagents to Bis(2-benzothiazolyl) Ketone: C - vs.EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 29 2010O -Alkylation Using Aryl Grignard Reagents Abstract The reaction between bis(2-benzothiazolyl) ketone (1) and a series of ring-substituted phenyl Grignard reagents gives, in considerable amount, the unexpected O -alkylation product derived from the attack of the Grignard reagent to thecarbonyl oxygen atom, thus extending the range of rarely reported cases in which O -alkylation can occur. The expected classic 1,2-addition product and that derived from O -alkylation have been obtained in a relative molar ratio dependent on the substituent on the phenyl ring. Bis(2-benzothiazolyl) aryl carbinols, the classic 1,2-addition products to the carbonyl group of 1, were obtained in high yield through an alternative synthetic route that permitted the limit imposed by O - vs. C -alkylation competition to be overcome. [source] Importance of tyrosine residues of Bacillus stearothermophilus serine hydroxymethyltransferase in cofactor binding and l - allo -Thr cleavageFEBS JOURNAL, Issue 18 2008Crystal structure, biochemical studies Serine hydroxymethyltransferase (SHMT) from Bacillus stearothermophilus (bsSHMT) is a pyridoxal 5,-phosphate-dependent enzyme that catalyses the conversion of l -serine and tetrahydrofolate to glycine and 5,10-methylene tetrahydrofolate. In addition, the enzyme catalyses the tetrahydrofolate-independent cleavage of 3-hydroxy amino acids and transamination. In this article, we have examined the mechanism of the tetrahydrofolate-independent cleavage of 3-hydroxy amino acids by SHMT. The three-dimensional structure and biochemical properties of Y51F and Y61A bsSHMTs and their complexes with substrates, especially l - allo -Thr, show that the cleavage of 3-hydroxy amino acids could proceed via C, proton abstraction rather than hydroxyl proton removal. Both mutations result in a complete loss of tetrahydrofolate-dependent and tetrahydrofolate-independent activities. The mutation of Y51 to F strongly affects the binding of pyridoxal 5,-phosphate, possibly as a consequence of a change in the orientation of the phenyl ring in Y51F bsSHMT. The mutant enzyme could be completely reconstituted with pyridoxal 5,-phosphate. However, there was an alteration in the ,max value of the internal aldimine (396 nm), a decrease in the rate of reduction with NaCNBH3 and a loss of the intermediate in the interaction with methoxyamine (MA). The mutation of Y61 to A results in the loss of interaction with C, and C, of the substrates. X-Ray structure and visible CD studies show that the mutant is capable of forming an external aldimine. However, the formation of the quinonoid intermediate is hindered. It is suggested that Y61 is involved in the abstraction of the C, proton from 3-hydroxy amino acids. A new mechanism for the cleavage of 3-hydroxy amino acids via C, proton abstraction by SHMT is proposed. [source] Multifunctional Triphenylamine/Oxadiazole Hybrid as Host and Exciton-Blocking Material: High Efficiency Green Phosphorescent OLEDs Using Easily Available and Common MaterialsADVANCED FUNCTIONAL MATERIALS, Issue 17 2010Youtian Tao Abstract A new triphenylamine/oxadiazole hybrid, namely m -TPA- o -OXD, formed by connecting the meta -position of a phenyl ring in triphenylamine with the ortho -position of 2,5-biphenyl-1,3,4-oxadiazole, is designed and synthesized. The new bipolar compound is applicable in the phosphorescent organic light-emitting diodes (PHOLEDs) as both host and exciton-blocking material. By using the new material and the optimization of the device structures, very high efficiency green and yellow electrophosphorescence are achieved. For example, by introducing 1,3,5-tris(N -phenylbenzimidazol-2-yl)benzene (TPBI) to replace 2, 9-dimethyl-4,7-diphenyl-1, 10-phenanthroline (BCP)/tris(8-hydroxyquinoline)aluminium (Alq3) as hole blocking/electron transporting layer, followed by tuning the thicknesses of hole-transport 1, 4-bis[(1-naphthylphenyl)amino]biphenyl (NPB) layer to manipulate the charge balance, a maximum external quantum efficiency (,EQE,max) of 23.0% and a maximum power efficiency (,p,max) of 94.3 lm W,1 are attained for (ppy)2Ir(acac) based green electrophosphorescence. Subsequently, by inserting a thin layer of m -TPA- o -OXD as self triplet exciton block layer between hole-transport and emissive layer to confine triplet excitons, a ,EQE,max of 23.7% and ,p,max of 105 lm W,1 are achieved. This is the highest efficiency ever reported for (ppy)2Ir(acac) based green PHOLEDs. Furthermore, the new host m -TPA- o -OXD is also applicable for other phosphorescent emitters, such as green-emissive Ir(ppy)3 and yellow-emissive (fbi)2Ir(acac). A yellow electrophosphorescent device with ,EQE,max of 20.6%, ,c,max of 62.1 cd A,1, and ,p,max of 61.7 lm W,1, is fabricated. To the author's knowledge, this is also the highest efficiency ever reported for yellow PHOLEDs. [source] Microbial degradation of isoproturon and related phenylurea herbicides in and below agricultural fieldsFEMS MICROBIOLOGY ECOLOGY, Issue 1 2003Sebastian R Sørensen Abstract The phenylurea herbicides are an important group of pesticides used extensively for pre- or post-emergence weed control in cotton, fruit and cereal crops worldwide. The detection of phenylurea herbicides and their metabolites in surface and ground waters has raised the awareness of the important role played by agricultural soils in determining water quality. The degradation of phenylurea herbicides following application to agricultural fields is predominantly microbial. However, evidence suggests a slow degradation of the phenyl ring, and substantial spatial heterogeneity in the distribution of active degradative populations, which is a key factor determining patterns of leaching losses from agricultural fields. This review summarises current knowledge on the microbial metabolism of isoproturon and related phenylurea herbicides in and below agricultural soils. It addresses topics such as microbial degradation of phenylurea herbicides in soil and subsurface environments, characteristics of known phenylurea-degrading soil micro-organisms, and similarities between metabolic pathways for different phenylurea herbicides. Finally, recent studies in which molecular and microbiological techniques have been used to provide insight into the in situ microbial metabolism of isoproturon within an agricultural field will be discussed. [source] Efficient and Long-Living Light-Emitting Electrochemical CellsADVANCED FUNCTIONAL MATERIALS, Issue 9 2010Rubén D. Costa Abstract Three new heteroleptic iridium complexes that combine two approaches, one leading to a high stability and the other yielding a high luminescence efficiency, are presented. All complexes contain a phenyl group at the 6-position of the neutral bpy ligand, which holds an additional, increasingly bulky substituent on the 4-position. The phenyl group allows for intramolecular ,,, stacking, which renders the complex more stable and yields long-living light-emitting electrochemical cells (LECs). The additional substituent increases the intersite distance between the cations in the film, reducing the quenching of the excitons, and should improve the efficiency of the LECs. Density functional theory calculations indicate that the three complexes have the desired ,,, intramolecular interactions between the pendant phenyl ring of the bpy ligand and the phenyl ring of one of the ppy ligands in the ground and the excited states. The photoluminescence quantum efficiency of concentrated films of the complexes improves with the increasing size of the bulky groups indicating that the adopted strategy for improving the efficiency is successful. Indeed, LEC devices employing these complexes as the primary active component show shorter turn-on times, higher efficiencies and luminances, and, surprisingly, also demonstrate longer device stabilities. [source] Novel Sulfonamide Derivatives as Inhibitors of Histone DeacetylaseHELVETICA CHIMICA ACTA, Issue 7 2005Inhibition of the enzyme histone deacetylase (HDAC) is emerging as a novel approach to the treatment of cancer. A series of novel sulfonamide derivatives were synthesized and evaluated for their ability to inhibit human HDAC. Compounds were identified which are potent enzyme inhibitors, with IC50 values in the low nanomolar range against enzyme obtained from HeLa cell extracts, and with antiproliferative effects in cell culture. Extensive characterization of the structure,activity relationships of this series identified key requirements for activity. These include the direction of the sulfonamide bond and substitution patterns on the central phenyl ring. The alkyl spacer between the aromatic head group and the sulfonamide functionality also influenced the HDAC inhibitory activity. One of these compounds, m11.1, also designated PXD101, has entered clinical trials for solid tumors and haematological malignancies. [source] Crystal Structures and Magnetic Properties of Nitronyl Nitroxide RadicalsHELVETICA CHIMICA ACTA, Issue 4 2003Alexander Zakrassov The crystal structures and magnetic properties of the nitronyl nitroxide radicals 4,5-dihydro-4,4,5,5-tetramethyl-3-oxido(1H -imidazol-1-yloxyl) (1), 4,5-dihydro-2,4,4,5,5-pentamethyl-3-oxido(1H -imidazol-1-yloxyl) (2), 2-(4-chlorophenyl)-4,5-dihydro-4,4,5,5-tetramethyl-3-oxido(1H -imidazol-1-yloxyl) (3), and 4,5-dihydro-2-(2-hydroxy-5-nitrophenyl)-4,4,5,5-tetramethyl-3-oxido(1H -imidazol-1-yloxyl) (4) are reported. Compound 1 has two polymorphic forms: the , phase is monoclinic (P21/n space group), with a single molecule in the asymmetric unit, and the , phase is monoclinic (P21/c space group), with four molecules in the asymmetric unit. In the two polymorphs, the molecules are arranged in dimers formed by hydrogen bonds of the type CH,,,ON. The crystal structure of 3 contains layers of antiparallel ribbons of molecules. Compound 4 crystallizes with solvent molecules, and an intramolecular hydrogen bond is formed between the 2-OH group of the phenyl ring and the nitroxide O-atom. Compound 4 also loses the two O-atoms of the nitroxide moiety upon heating to 90°. Magnetic measurements showed that both , and , polymorphs of 1 exhibit antiferromagnetic coupling. The best fit to the experimental data was obtained using BleanyBower's singlet-triplet model (H=,2JSaSb): J=,11.2,K for the , phase and J=,15.0,K for the , phase. Compounds 3 and 4 show no evidence for spin coupling. [source] Crystal and molecular structures of atropisomeric N -aryl-1,2,3,4-tetrahydro-3,3-dimethyl-2,4-quinolinedionesHETEROATOM CHEMISTRY, Issue 3 2008Mario Cetina The crystal structures of N -aryl-1,2,3,4-tetrahydro-3,3-dimethyl-2,4-quinolinediones bearing methoxy- (1), methyl- (2), and chloro- (3) substituents in 2,-position of the phenyl ring have been determined by X-ray crystal structure analysis. The heterocyclic ring in 1,3 adopts an envelope conformation, with the smallest ring puckering in the ortho-chloro derivative 3. The N -aryl ring is almost perpendicular with respect to the quinoline-2,4-dione ring. The corresponding dihedral angle values are 83.2(1)°, 80.0(9)°, and 83.4(2)° in 1, 2 and 3, respectively. The hydrogen bond of CH,,,O type joins the molecules of the ortho-methoxy derivative 1 into dimers. The supramolecular structure also contains two CH,,,, interactions that link the hydrogen-bonded dimers into sheets. In ortho-methyl derivative 2, one CH,,,, interaction generates infinite chains, whereas two CH,,,O hydrogen bonds and three CH,,,, interactions in the ortho-chloro derivative 3 form three-dimensional framework. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:325,331, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20436 [source] Reaction of 4-benzylidene-2-methyl-5-oxazolone with amines, Part 2: Influence of substituents in para-position in the phenyl ring and a substituent on amine nitrogen atom on the reaction kineticsINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 3 2002B. Bet, akowska An influence of a structure of the amine (benzylamine, N -methyl-benzylamine, N -isopropyl-benzylamine, N -methyl-butylamine, N -ethyl-butylamine, sec -butylamine, and tert -butylamine) on a rate constant of the ring-opening reaction of 4-benzylidene-2-methyl-5-oxazolone (Ox) was studied. The good correlation between logarithm of the rate constants and Charton's steric substituent constant , as well as good correlation with a form of the simple branching equation indicate that there is a steric effect because of substitution at C1 carbon atom of nucleophile which decreases the reaction rate. Additionally, an influence of a structure of the benzylidene moiety of Ox on a rate of the oxazolone ring-opening reaction was studied. The substituents (OH, OCH3, N(CH3)2, Cl, NO2) in para-position of the phenyl ring of Ox substantially modified the rate of the reaction with benzylamine in acetonitrile. The rate of the Ox ring-opening reaction decreased with increase of the electron-donating properties of the substituent. A good correlation between the rate constants of the reaction of 4-(4,-substituted-benzylidene)-2-methyl-5-oxazolones with benzylamine and the electron density at the reaction center (carbon C5 of the oxazolone ring), calculated using ab initio method, and the Hammett substituent constants, and CR equation were established. © 2002 Wiley Periodicals, Inc. Int J Chem Kinet 34: 148,155, 2002; DOI 10.1002/kin.10039 [source] Interaction of FeO+ cation with benzene, aniline, and 3-methylaniline: DFT study of oxygen insertion mechanismINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 11 2008Karolina Kwapien Abstract The reaction pathways and energetics for oxygen insertion into CH bond in benzene, aniline, and 3-methylaniline by FeO+ in the gas phase were investigated by means of the DFT methodology with the B3LYP exchange-correlation functional and 6-311G** basis set. The main aim of this work was to elucidate the influence of substituents in phenyl ring on stationary points along the energy profile on sextet and quartet surfaces for the reaction of FeO+ with substituted benzenes. The studies show that the amino and methyl groups change the energetics of oxygen insertion by lowering the energy profile along the reaction pathway. The substituents studied in this work facilitate the insertion of oxygen into the aromatic CH bond by stabilizing the intermediate sigma complex (,-complex), the amino group being by far more effective. On the other hand, both functional groups increase the activation energy of the rate-determining step in the gas phase, so that they have unfavorable influence on the kinetics. The comparison of the energy diagrams for the sextet and quartet spin states indicates the dominance of the low-spin reactivity in oxygen insertion into aromatic CH bond. Aniline and 3-methylaniline oxidation occurs via electrophilic addition while the conversion of benzene to phenol by FeO+ is mediated by a ,-complex with mixed radical and cationic character. Present results are also discussed in the context of oxyferryl group reactivity. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Stereoselective Chemoenzymatic Preparation of ,-Amino Esters: Molecular Modelling Considerations in Lipase-Mediated Processes and Application to the Synthesis of (S)-DapoxetineADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010María Rodríguez-Mata Abstract A wide range of optically active 3-amino-3-arylpropanoic acid derivatives have been prepared by means of a stereoselective chemoenzymatic route. The key step is the kinetic resolution of the corresponding ,-amino esters. Although the enzymatic acylations of the amino group with ethyl methoxyacetate showed synthetically useful enantioselectivities, the hydrolyses of the ester group catalyzed by lipase from Pseudomonas cepacia have been identified as the optimal processes concerning both activity and enantioselectivity. The enantiopreference of this lipase in these reactions has been explained, at the molecular level, by using a fragment-based approach in which the most favoured binding site for a phenyl ring and the most stable conformation of the 3-aminopropanoate core nicely match the (S)-configuration of the major products. The conversion and enantioselectivity values of the enzymatic reactions have been compared in order to understand the influence of the different substitution patterns present in the phenyl ring. This chemoenzymatic route has been successfully applied to the preparation of a valuable intermediate in the synthesis of (S)-dapoxetine, which has been chemically synthesised in excellent optical purity. [source] Synthesis of imidazole and imidazolium porphyrinsJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2006Virginia Seng A new porphyrin compound, where an imidazole group was attached through the 1-position nitrogen to a phenyl ring located on the porphyrin periphery has been synthesized and characterized. The second nitrogen on the imidazole is available for further chemistry as demonstrated by the attachment of bromopentane forming the imidazolium porphyrin complex. This is the first example of an imidazolium group covalently attached to the porphyrin periphery in which the porphyrin is attached through the nitrogen on the imidazole ring rather than a carbon atom. [source] Synthesis and nuclear magnetic resonance spectroscopic studies of 1-arylpyrrolesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2000Chang Kiu Lee A series of m - and p -substituted 1-phenyl, 1-benzyl, 1-benzoyl, and 1-(2-phenylethyl)pyrroles was prepared and their 1H and 13C nmr spectroscopic characteristics were examined. In general, good correlations were observed between the chemical shift values of the ,H and the ,C of pyrroles [except 1-(2-phenylethyl)pyrroles] and the Hammettt ,. The observation may be explained in terms of the electronic effects of the substituents which are transmitted through bonds and through space by interaction of the p orbitals between ,Cs of the pyrrole ring and m - and pCs of the phenyl ring. Substituent constants of 1-pyrrolyl, 1-pyrrolylmethyl, and 1-pyrroloyl groups for the 1H and 13C chemical shifts of phenyl ring are also presented. [source] Ortho -[18F]Fluoronitrobenzenes by no-carrier-added nucleophilic aromatic substitution with K[18F]F,K222,A comparative studyJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 13 2002M. Karramkam Abstract The scope of the nucleophilic aromatic ortho -fluorinations from the corresponding ortho -halonitrobenzene precursors (halo-to-fluoro substitutions) with no-carrier-added [18F]fluoride ion as its activated K[18F]F,K222 complex has been evaluated via the radiosynthesis of ortho -[18F]fluoronitrobenzene, chosen as a model reaction. The parameters studied include the influence of the leaving group in the ortho position of the phenyl ring (,Cl, ,Br, ,l), the quantity of precursor used, the type of activation (conventional heating or microwave irradiations), the solvent, the temperature and the reaction time. The iodo-precursor was completely unreactive and the bromo-precursor gave only low incorporation (<10%) in the optimal conditions used (conventional heating at 145°C or microwave activation, 100 W for 120 s). Only the chloro-precursor was found reactive in the conditions described above and up to 70% yield was observed for the formation of ortho -[18F]fluoronitrobenzene ([18F]- 1). In all the experiments, the unwanted ortho -[18F]fluoro-halobenzenes, potentially resulting from the nitro-to-fluoro substitution, could not be detected. These results will be applied for the radiosynthesis of 5-[18F]fluoro-6-nitroquipazine, a potent radioligand for the imaging of the serotonin transporter with PET. Copyright © 2002 John Wiley & Sons, Ltd. [source] Substituent effect and multisite protonation in the fragmentation of alkyl benzoatesJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 3 2002Chagit Denekamp Abstract The dissociation of protonated alkyl benzoates (para H, CN, OMe and NO2) into protonated benzoic acids and alkyl cations was studied in the gas phase. It was found that the product ratio depends on the substituent at the para position of the phenyl ring. The substituent effect is probably the result of the formation of an ion,neutral complex intermediate that decomposes to an ion and a neutral, according to the relative proton affinities of the two moieties. The experimental results and theoretical calculations indicate that the favored protonation site in these compounds is the ester's carbonyl and that proton transfer from the phenyl ring to the ester group is very likely to occur under chemical ionization conditions. It is most probable that the carbonyl protonated form is a common intermediate in the fragmentation process, regardless of the protonation site. Copyright © 2002 John Wiley & Sons, Ltd. [source] Structural basis for preferential binding of non- ortho -substituted polychlorinated biphenyls by the monoclonal antibody S2B1JOURNAL OF MOLECULAR RECOGNITION, Issue 4 2005Jean-Luc Pellequer Abstract Polychlorinated biphenyls (PCBs) are a family of 209 isomers (congeners) with a wide range of toxic effects. In structural terms, they are of two types: those with and those without chlorines at the ortho positions (2, 2,, 6 and 6,). Only 20 congeners have no ortho chlorines. Three of these are bound by the aryl hydrocarbon receptor and are one to four orders of magnitude more toxic than all others. A monoclonal antibody, S2B1, and its recombinant Fab have high selectivity and nanomolar binding affinities for two of the most toxic non- ortho -chlorinated PCBs, 3,4,3,,4,-tetrachlorobiphenyl and 3,4,3,,4,,5,-pentachlorobiphenyl. To investigate the basis for these properties, we built a three-dimensional structure model of the S2B1 variable fragment (Fv) based on the high-resolution crystallographic structures of antibodies 48G7 and N1G9. Two plausible conformations for the complementarity-determining region (CDR) H3 loop led to two putative PCB-binding pockets with very different shapes (models A and B). Docking studies using molecular mechanics and potentials of mean force (PMF) indicated that model B was most consistent with the selectivity observed for S2B1 in competition ELISAs. The binding site in model B had a deep, narrow pocket between VL and VH, with a slight constriction at the top that opened into a wider pocket between CDRs H1 and H3 on the antibody surface. This binding site resembles those of esterolytic antibodies that bind haptens with phenyl rings. One phenyl ring of the PCB fits into the deep pocket, and the other ring is bound in the shallower one. The bound PCB is surrounded by the side chains of TyrL91, TyrL96 and TrpH98, and it has a ,-cation interaction with ArgL46. The tight fit of the binding pocket around the ortho positions of the bound PCBs indicates that steric hindrance of ortho chlorines in the binding site, rather than induced conformational change of the PCBs, is responsible for the selectivity of S2B1. Copyright © 2005 John Wiley & Sons, Ltd. [source] Study of the conformational profile of the norbornane analogues of phenylalanineJOURNAL OF PEPTIDE SCIENCE, Issue 6 2002Arnau Cordomí Abstract The conformational profile of the eight stereoisomeric 2-amino-3-phenylnorbornane-2-carboxylic acids (2-amino-3-phenylbicyclo[2.2.1]heptane-2-carboxylic acids) has been assessed by computational methods. These molecules constitute a series of four enantiomeric pairs that can be considered as rigid analogues of either L - or D -phenylalanine. The conformational space of their N -acetyl methylamide derivatives has been explored within the molecular mechanics framework, using the parm94 set of parameters of the AMBER force field. Local minimum energy conformations have been further investigated at the ab initio level by means of the Hartree-Fock and second order Moller-Plesset perturbation energy calculations using a 6,31G(d) basis set. The results of the present work suggest that the bulky norbornane structure induces two kinds of conformational constraints on the residues. On one hand, those of a steric nature directly imposed by the bicycle on the peptide backbone and, on the other hand, those that limit the orientations attainable by the phenyl ring which, in turn, reduces further the flexibility of the peptide backbone. A comparative analysis of the conformational profile of the phenylnorbornane amino acids with that of the norbornane amino acids devoid of the ,-phenyl substituent suggests that the norbornane system hampers the residue to adopt extended conformations in favour of C7-like structures. However, the bicycle itself does not impart a clear preference for any of the two possible C7 minima. It is the aromatic side chain, which is forced to adopt an almost eclipsed orientation, that breaks this symmetry introducing a marked preference for a single region of the (,, ,) conformational space in each of the phenylalanine norbornane analogues investigated. Copyright © 2002 European Peptide Society and John Wiley & Sons, Ltd. [source] Influence of substituents on the infrared stretching frequencies of carbonyl group in esters of benzoic acidJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 10 2006Vilve Nummert Abstract Infrared spectra of 25 substituted phenyl esters of benzoic acid C6H5CO2C6H4 -X (XH, 3-Cl, 3-F, 3-CN, 3-NO2, 3-CH3, 3-OH, 3-NH2, 4-Cl, 4-F, 4-NO2, 4-CN, 4-OCH3, 4-CH3, 4-NH2, 2-Cl, 2-F, 2-I, 2-NO2, 2-CF3, 2-CN, 2-CH3, 2-OCH3, 2-N(CH3)2, 2-C(CH3)3), 8 alkyl benzoates C6H5CO2R (XCH3, CH2CH3, CH2Cl, CH2CN, CH2CCH, CH2CH2Cl, CH2CH2OCH3, CH2C6H5), and 22 phenyl esters of substituted benzoic acids X-C6H4CO2C6H5 (X3-Cl, 3-NO2, 3-CH3, 3-N(CH3)2, 4-F, 4-Cl, 4-Br, 4-NO2, 4-CH3, 4-C(CH3)3, 4-OCH3, 4-NH2, 2-Cl, 2-F, 2-Br, 2-I, 2-NO2, 2-CN, 2-CF3, 2-CH3, 2-OCH3, 2-NH2) were recorded in tetrachloromethane in the region of 400,4000,cm,1. Carbonyl stretching frequencies ,CO for meta - and para -substituted phenyl esters of benzoic acid and phenyl esters of meta -substituted benzoic acids were shown to correlate with the substituent constants ,o. The influence of the through resonance effect on ,CO was found to be important in the case of +Rpara substituents in the benzoyl part of phenyl benzoates as well. The carbonyl stretching frequencies of ortho derivatives in phenoxy part were shown to correlate with the inductive substituent constant ,I only. In the benzoyl part of the esters the carbonyl stretching frequencies of cis and trans conformers (relative to the carbonyl group) of ortho derivatives were nicely described by dual parameter equations: (,CO)cis,=,(,CO)o,+,c1,I,+,c3,and (,CO)trans,=,(,CO)o,+,c1,p+,+,c3, (R,=,0.99). The trans isomers of phenyl esters of ortho -substituted benzoic acids showed direct resonance similar to that for para derivatives. The positive steric term found for both the cis and trans conformers could be considered as measure of the steric inhibition of resonance between the phenyl ring and the carboxy-group caused by bulky ortho substituents. The existence of cis/trans conformations was supported by frequency calculations with Density Functional Theory (DFT) method at B3LYP/6-311+G** level for the ortho -substituted benzoates. In the case of alkyl benzoates good correlations of ,CO values were obtained when both the Taft ,* and the steric constants were used. For meta - and para -substituted phenyl benzoates s - trans conformation where the plane of the benzene ring in the benzoyl part of the ester is coplanar with the carbonyl bond plane and the plane of the benzene ring in the phenoxy part is twisted nearly perpendicular relative to the carbonyl bond plane was supported. Copyright © 2006 John Wiley & Sons, Ltd. [source] Fluorene-based liquid crystalline networks with linearly polarized blue emissionJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2007Marta Millaruelo Abstract A series of fluorene-based luminophores containing methacrylic end groups have been prepared and incorporated into uniaxially oriented liquid crystalline films by in situ photopolymerization. Various structural modifications on the 2-(4-cyanophenyl)fluorene core, which include alkyl chains at the 9-position and elongation of the rigid core with one additional phenyl ring, have been investigated to generate emitters with adjusted liquid crystal compatibility, improved luminescence and dichroic properties. Polarized blue-emitting films were produced that had an acceptable photostability, and it was found that the polarization emission was better for samples with low (5%) cross-linker contents. Polarization of the luminescence was favored by the liquid crystalline properties of the luminophore. In addition, the detrimental effect of the alkyl substituent at the fluorene core on the mesomorphism and on the emission polarization can be overcome by lengthening the ,-system. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4804,4817, 2007 [source] Gradient graft copolymers derived from PEO-based macromonomersJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 4 2006Dorota Neugebauer Abstract Atom transfer radical polymerization (ATRP) of two poly(ethylene oxide) (PEO) macromonomers, with different polymerization degrees (DPn) and different end groups, was conducted in solution via the grafting through method. Selection of a PEO methacrylate with a methyl end-group (PEOMeMA, DPPEO = 23) and a PEO acrylate end-capped by a phenyl ring (PEOPhA, DPPEO = 4) for the copolymerization led to a spontaneous gradient of PEO grafts along the copolymer backbone. Such a composition was formed because of significantly different reactivities of the two PEO macromonomers. The resulting copolymer has PEOMeMA at one end of the polymer chain, gradually changing through hetero-sequences of PEOPhA at the other chain end. An increase in the initial feed ratio of PEO acrylate reduced the rate of change in the shape of the gradient. Amorphous,crystalline structure in the copolymers was demonstrated by DSC and WAXS. The mechanical measurements of copolymers consisting of an amorphous PEOPhA and crystallizable PEOMeMA segments indicated elastomeric properties in the range of a soft rubber (G, , 104 Pa, G, , G,). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1347,1356, 2006 [source] Synthesis and polymerization reactions of cyclic imino ethers.JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2006Abstract Homopolyaddition reactions of AB-type monomers containing a 2-oxazoline and a phenol group in different positions of the phenyl ring, namely, 2-(4-hydroxyphenyl)-2-oxazoline, 2-(3-hydroxyphenyl)-2-oxazoline, 2-(2-hydroxyphenyl)-2-oxazoline, and 2-(4-hydroxyphenyl)-4,4-dimethyl-2-oxazoline, were studied. Except for 2-(4-hydroxyphenyl)-4,4-dimethyl-2-oxazoline, the reaction carried out in bulk or a solution of highly boiling solvents resulted in the formation of poly(ether amide)s with molecular weights in the range of 103 to 104 as measured by vapor pressure osmometry and gel permeation chromatography. A mechanism of the growth reaction, including a nucleophilic attack of a phenol group to a 2-oxazoline ring in the 5-position, was suggested. The polymerization was accompanied by a side reaction of the amido groups formed by the primary reaction of the 2-oxazoline ring. This led to branching of the main chain. The thermal properties of the prepared polymers were evaluated. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 343,355, 2006 [source] Novel thermally stable poly(amine hydrazide)s and poly(amine-1,3,4-oxadiazole)s for luminescent and electrochromic materialsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2005Guey-Sheng Liou Abstract We describe the preparation, characterization, and luminescence of four novel electrochromic aromatic poly(amine hydrazide)s containing main-chain triphenylamine units with or without a para-substituted N,N -diphenylamino group on the pendent phenyl ring. These polymers were prepared from either 4,4,-dicarboxy-4,- N,N -diphenylaminotriphenylamine or 4,4,-dicarboxytriphenylamine and the respective aromatic dihydrazide monomers via a direct phosphorylation polycondensation reaction. All the poly(amine hydrazide)s were amorphous and readily soluble in many common organic solvents and could be solution-cast into transparent and flexible films with good mechanical properties. These poly(amine hydrazide)s exhibited strong ultraviolet,visible absorption bands at 346,348 nm in N -methyl-2-pyrrolidone (NMP) solutions. Their photoluminescence spectra in NMP solutions or as cast films showed maximum bands around 508,544 and 448,487 nm in the green and blue region for the two series of polymers. The hole-transporting and electrochromic properties were examined by electrochemical and spectroelectrochemical methods. All obtained poly(amine hydrazide)s and poly(amine-1,3,4-oxadiazole)s exhibited two reversible oxidation redox couples at 0.8 and 1.24 V vs. Ag/AgCl in acetonitrile solution and revealed excellent stability of electrochromic characteristics, changing color from original pale yellow to green and then to blue at electrode potentials of 0.87 and 1.24 V, respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3245,3256, 2005 [source] | ||||||||||||||||||||||||||||||||||||||||||||||