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Aryl Groups (aryl + groups)
Selected AbstractsChemInform Abstract: Rhodium(II)-Catalyzed Transylidation of Aryliodonium Ylides: Electronic Effects of Aryl Groups Determine Their Thermodynamic Stabilities.CHEMINFORM, Issue 34 2008Masahito Ochiai Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Lewis-Acid-Catalyzed Rearrangement of Arylvinylidenecyclopropanes: Significant Influence of Substituents and Electronic Nature of Aryl Groups.CHEMINFORM, Issue 21 2007Yun-Peng Zhang Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Synthesis, Characterization, and Protonation Reactions of Ar-BIAN and Ar-BICAT Diimine Platinum Diphenyl ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 9 2010Jerome Parmene Abstract PtII diphenyl complexes (N,N)PtPh2 [N,N = diimines Ar,N=C(An)C=N,Ar with Ar = substituted aryl groups] have been prepared and characterized by 1H, 13C, and 195Pt NMR spectroscopy. The 195Pt NMR spectroscopic data establish the electronic influence exerted by substituents at the backbone of the diimine ligand system to the metal center. When compared to diimines Ar,N=CMe,CMe=N,Ar, the electron-withdrawing ability of the Ar-BIAN ligand and the electron-donating ability of the O,O-heterocyclic Ar-BICAT systems are demonstrated. Trends in 195Pt NMR chemical shifts suggest that electronic tuning of the metal center is better achieved through variations of the diimine backbone substituents rather than variation of the substituents at the N-Aryl groups. Protonation of (N,N)PtPh2 in dichloromethane/acetonitrile at ,78 °C furnishes the corresponding PtIV hydrides (N,N)PtPh2H(NCMe)+. The PtIV hydrides liberate benzene with the formation of (N,N)PtPh(NCMe)+ when the temperature is raised. A second protonation and rapid benzene elimination produces the dicationic PtII species (N,N)Pt(NCMe)22+ at approximately 50 °C. Protonation of (N,N)PtPh2 in the absence of acetonitrile results in the clean formation of (N,N)PtPh(,2 -C6H6)+ at temperatures that depend on the steric hindrance provided by the alkyl substituents at the diimine N-aryl groups. These findings support the notion that the metal is the kinetically preferred site of protonation. The results qualitatively agree with a recent mechanistic study of protonation-induced reactions of (diimine)PtPh2 complexes that bear simple methyl substituents at the diimine backbone. Several compounds have been crystallographically characterized. All complexes have the expected square planar environment at the metal. Modest variations in the metric parameters suggest that the Ar-BICAT system has a weaker trans influence than the Ar-BIAN and Ar-DAB systems. [source] Pyrazolate-Based Dinucleating Ligands in L2M2 Scaffolds: Effects of Bulky Substituents and Coligands on Structures and M···H,C InteractionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2004Jens C. Röder Abstract A series of nickel(II) and palladium(II) complexes [L2M2]2+ have been prepared and structurally characterized, where L is a pyrazolate ligand with bulky 2,6-dimethyl- or 2,6-di(isopropyl)anilinomethyl side arms. Coordinating counter anions such as chloride can bind to axial sites of the dinickel species in a solvent-dependent process, giving rise to five-coordinate high-spin metal ions. In the case of weakly coordinating anions, the metal ions are found in roughly square-planar environments, and the structures are governed by the tendency of the bulky aryl groups to avoid each other, which forces the methyl or isopropyl substituents in the aryl 2- and 6-positions to approach the metal ions from the axial directions. This leads to drastic low-field shifts of the respective 1H NMR signals, e.g. , = 7.86 ppm for the isopropyl ,CH which comes in close proximity to the low-spin nickel(II) center. The relevance of such low-field NMR resonances of protons close to the axial sites of d8 metal ions for possible three-center four-electron M···H,C hydrogen bonds involving the filled d orbital of the metal ion is discussed. In the present case, attractive M···H interactions are assumed to be of no major significance. This was corroborated by the structure of a further [L2Ni2]2+ type complex where the anilinomethyl side arms bear only a single 2-isopropyl group, which was found rotated away from the metal. Additional spectroscopic and electrochemical properties of the various complexes are reported. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Synthesis and Molecular Structures of Nickel(II) and Cobalt(III) Complexes with 2-(Arylimino)-3-(hydroxyimino)butaneEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2003Ennio Zangrando Abstract We report new series of NiII and CoIII complexes with nitrogen-donor chelating ligands of the (E,E)-2-(arylimino)-3-(hydroxyimino)butane type (Ar,N,N,OH). These ligands are characterized by a hydrophilic (OH group) and a hydrophobic region (aryl group). NiII derivatives were obtained either as trimers of formula [Ni3(Ar,N,N,OH)3Br4(OH)][Br], with the hydrophobic groups oriented on the same side, or as bis(chelated) derivatives with cis geometry, depending on the steric hindrance of the aryl groups. CoIII complexes were obtained only as bis(chelated) derivatives, with the two ligands coplanar. The "iso -oriented" arrangement of ligands in bis(chelated) CoIII complexes is favored by weak interactions between the two ligands, namely O,H···O hydrogen bond and stacking interactions between the aryl groups. CoIII complexes might find application as catalysts for living or controlled radical polymerization of polar olefins, and preliminary results are reported. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] One-Pot Synthesis of 3-Aryltetramic AcidsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2010Aurélie Mallinger Abstract Tetramic acids substituted in the 3-position by various aryl groups were prepared in one-pot from amino esters and methyl arylacetates, by treatment with potassium tert -butoxide. A tandem process, involving the formation of an amide and a condensation reaction, is likely to occur. N -Unsubstituted tetramic acids were obtained from adducts containing a N -(2,4-dimethoxybenzyl) group. [source] Reusable, Polystyrene-Resin-Supported, Palladium-Catalyzed, Atom-Efficient Cross-Coupling Reaction of Aryl Halides with TriarylbismuthsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2010Wen-Jun Zhou Abstract A rapid, atom-efficient, cross-coupling reaction of triarylbismuths with aryl bromides or aryl iodides was reported, and the reaction involves the use of a catalytic amount of polystyrene-supported palladium in the presence of KF as base in DMSO at 105 °C in an open atmosphere. All three aryl groups of the triarylbismuths participated in the reaction and produced polyfunctional biaryls in excellent yields. The polymeric catalyst can be easily separated from the reaction mixture and reused more than 10 times without showing any obvious decrease in activity. [source] Isolation of Phlorin-Dipyrrin Conjugates from the Acid-Catalyzed Condensation of Dipyrromethanes and AldehydesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2005Daniel T. Gryko Abstract The product distribution of the acid-mediated condensation of dipyrromethanes and aldehydes was studied and a novel type of macrocycle phlorin-dipyrrin conjugate was isolated and identified by X-ray analysis. The generality of its formation from sterically hindered dipyrromethanes and pentafluorophenyldipyrromethane was demonstrated. The influence of the meso -aryl groups on the stability of the phlorin was studied. The reported two-step synthesis of a phlorin derivative is one of the simplest routes leading to this type of molecules. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Non-Dipolar Behavior of Mesoionic Heterocycles: Synthesis and Tautomerism of 2-AlkylthioisomünchnonesEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 13 2004Martín Ávalos Abstract This paper describes a general preparation of a series of 1,3-thiazolium-4-olates, each bearing an alkyl group at C-2, through reactions between N -arylthiocarboxamides and ,-haloacyl halides. Unlike the 2-aryl-substituted derivatives, such alkylated mesoionic compounds exist in equilibria with their non-dipolar tautomers, the corresponding 2-alkylidene-1,3-thiazolidin-4-ones. The unambiguous characterization of such tautomers and their relative stabilities have now been assessed by spectroscopic and computational studies. The presence of o,o, -disubstituted aryl groups at N-3 of the heterocyclic ring slows down free rotation around the N,Ar bond, thus opening access to a promising class of non-biaryl atropisomers. Finally, treatment of N -arylthioformamides with ,-haloacyl halides gives rise to N -acylthioformamides instead of the corresponding mesoionic species. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Erratum: Synthesis of functional phosphines with ortho-substituted aryl groups: 2-RC6H4PH2 and 2-RC6H4P(SiMe3)2 (R = i -Pr- or t -Bu)HETEROATOM CHEMISTRY, Issue 5 2010Julien Dugal-Tessier The synthesis and characterization of 2-i-PrC6H4PCl2 (3), 2-t-BuC6H4PCl2 (4), 2-i-PrC6H4PH2 (5), 2-t-BuC6H4PH2 (6), 2-i-PrC6H4P(SiMe3)2 (7), and 2-t-BuC6H4P(SiMe3)2 (8) are described. © 2010 Wiley Periodicals, Inc. Heteroatom Chem 21:355,360, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20619, [source] Regioselective Palladium(0)-Catalyzed Cross-Coupling Reactions and Metal-Halide Exchange Reactions of Tetrabromothiophene: Optimization, Scope and LimitationsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009ng Thanh Tùng Abstract The Suzuki reaction of tetrabromothiophene with arylboronic acids provides a regioselective approach to various 5-aryl-2,3,4-tribromothiophenes, symmetrical 2,5-diaryl-3,4-dibromothiophenes, and tetraarylthiophenes. Unsymmetrical 2,5-diaryl-3,4-dibromothiophenes are prepared by Suzuki reaction of 5-aryl-2,3,4-tribromothiophenes. Tetraarylthiophenes containing two different types of aryl groups are obtained by Suzuki reactions of 2,5-diaryl-3,4-dibromothiophenes. During the optimization of the conditions of each individual reaction, the solvent, the catalyst and the temperature play an important role. In several cases, classical conditions [use of tetrakis(triphenylphosphane)palladium(0), Pd(PPh3)4, as the catalyst] gave excellent yields. The yields of those transformations which failed or proceeded sluggishly could be significantly improved by application of a new biarylmonophosphine ligand developed by Buchwald and co-workers. Regioselective metal-halide exchange reactions of tetrabromothiophene provide a convenient approach to various 2,5-disubstituted 3,4-dibromothiophenes. 5-Alkyl-2-trimethylsilyl-3,4-dibromothiophenes could be prepared in one pot by sequential addition of trimethylchlorosilane and alkyl bromides. The reaction of tetrabromothiophene with methyl chloroformate and subsequent Suzuki reactions afforded 3,4-diaryl-2,5-bis(methoxycarbonyl)thiophenes. [source] Enantioselective Reduction of Diaryl Ketones Catalyzed by a Carbonyl Reductase from Sporobolomyces salmonicolor and its Mutant EnzymesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2009Hongmei Li Abstract The carbonyl reductase from red yeast Sporobolomyces salmonicolor AKU4429 (SSCR) and its mutant enzymes effectively catalyzed the enantioselective reduction of diaryl ketones to give the corresponding chiral alcohols. Both conversion and enantioselectivity were dependent on the co-solvent in the reaction medium. Diaryl ketones with a para -substituent on one of the phenyl groups were reduced with high enantioselectivity (up to 99% ee), which is difficult to achieve using chemical methods such as chiral borane reduction, asymmetric hydrogenation or hydrosilylation. Mutation of SSCR at Q245 resulted in a higher amount of (S)-enantiomer in the products, and in the case of mutant Q245P with para -substituted diaryl ketones as substrate, this effect was so remarkable that the reduction enantiopreference was switched from (R) to (S). The present study provides valuable information about the catalytic properties of the carbonyl reductase SSCR toward the reduction of diaryl ketones, serving as basis for further engineering of this enzyme to develop efficient biocatalysts for highly enantiospecific reduction of diaryl ketones without high electronic dissymmetry or an ortho -substituent on one of the aryl groups. [source] A Convenient Synthesis of 2,2,,6,6,-Tetramethoxy- 4,4,-bis(dicyclohexylphosphino)-3,3,-bipyridine (Cy-P-Phos): Application in Rh-Catalyzed Asymmetric Hydrogenation of ,-(Acylamino)acrylatesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 4 2005Jing Wu Abstract The first example of the synthesis of an axially chiral bis(aryldicyclohexylphosphine) dioxide via catalytic hydrogenation of the optically resolved parent bis(aryldiphenylphosphine) dioxide was reported. The procedure for the synthesis of Cy-P-Phos (4d) has thus successfully avoided the need for an otherwise lengthy synthetic route owing to the ,-excessive nature of one of the aryl groups in the latter. The use of Cy-P-Phos in the Rh(I)-catalyzed asymmetric hydrogenation of the derivatives of methyl (Z)-2-acetamidocinnamate gave significantly higher rates of reaction as compared to the use of the previously reported optimal ligand Xyl-P-Phos (4c) whilst the level of enantioselectivity was essentially maintained. [source] New fluorene-based copolymers containing oxadiazole pendant groups: Synthesis, characterization, and polymer stabilityJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 18 2009Dmitrij Bondarev Abstract A series of fluorene-based copolymers containing hole blocking/electron transporting diphenyloxadiazole units were synthesized by means of Suzuki-Miyaura coupling of selected aromatic dibromo- and diboronato- derivatives catalyzed with a Pd(PPh3)4 catalyst. All of the copolymers with various composition of main-chain units were characterized by SEC chromatography, NMR, UV,vis, fluorescence and IR spectroscopy, and DSC. The emission stability of fluorene copolymers was improved by the replacement of alkyl groups on the C-9 carbon of fluorene with aryl groups or by the incorporation of anthracene units into the copolymer main chain. A comparison of luminescence properties of pristine and annealed thin layers of studied copolymers was performed. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 4532,4546, 2009 [source] Synthesis and characterization of a series of diverse poly(2-oxazoline)sJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2009Kristian Kempe Abstract This article describes the synthesis and characterization of a variety of new poly(2-oxazoline)s. With regard to functional polymers, 2-oxazolines represent an interesting class of monomers because of the easy variation of the substituent in 2-position. Starting from the corresponding nitriles, different 2-oxazolines were obtained containing a diverse set of 2-substituents, including thioether bonds (M11), trifluoromethyl groups (M8, M10), and alkyl- or aryl groups (M1,M7). The subsequent polymerization of the majority of these monomers proceeded in a living manner, which was demonstrated by linear first-order kinetics, a linear increase of molar mass with conversion, and relatively narrow molar mass distributions. In addition, selected thermal and surface properties of the polymers were studied utilizing DSC and contact-angle measurements to determine the effects of different 2-substituents on the macroscopic properties. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3829,3838, 2009 [source] 1H and 13C NMR spectral assignments of some novel 2,4,6,8-tetraaryl-3,7-diazabicyclo[3.3.1]nonan-9-one derivativesMAGNETIC RESONANCE IN CHEMISTRY, Issue 8 2008Paramasivam Parthiban Abstract The 1H and 13C NMR spectra of 2,4,6,8-tetraaryl-3,7-diazabicyclo[3.3.1]nonan-9-ones (1,2), oximes (3,8) and O -benzyl oximes (9,12) were recorded. The chemical shifts were unambiguously assigned using 1D and 2D NMR spectral data. The results clearly indicate that the compounds exist in chair-boat conformation with equatorial and axial orientation of the aryl groups in the chair and boat forms, respectively. Since the molecules are flexible and dynamic in solution, the chair and boat forms are mutually interconvertible. In 3,12, because of the effect of oximation/oximination, all the protons in the heterobicyclic systems gave distinct signals except the benzylic protons of the boat form. In all synthesized compounds, the aryl group protons at C-6,8 are shielded by the aryl groups at C-2,4 and therefore appear in the lower frequency region than the aryl groups at C-2,4. Copyright © 2008 John Wiley & Sons, Ltd. [source] 13C and 15N NMR chemical shifts of 1-(2,,4,-dinitrophenyl) and 1-(2,,4,,6,-trinitrophenyl) pyrazoles in the solid state and in solution,MAGNETIC RESONANCE IN CHEMISTRY, Issue 7 2008M. Ángeles García Abstract The 13C and 15N CPMAS NMR spectra of 18 pyrazoles substituted at position 1 by dinitrophenyl and trinitrophenyl (picryl) groups have been recorded. To help in the assignments, some of these compounds were studied in DMSO- d6 solution. Phenomena such as the conformation of the N -aryl groups and broadening of splittings due to quadrupolar nuclei are discussed. Copyright © 2008 John Wiley & Sons, Ltd. [source] Tris(4-bromophenyl)aminium hexachloridoantimonate (`Magic Blue'): a strong oxidant with low inner-sphere reorganizationACTA CRYSTALLOGRAPHICA SECTION C, Issue 7 2010Mauricio Quiroz-Guzman Both the radical cation tris(4-bromophenyl)aminium hexachloridoantimonate (`Magic Blue'), (C18H12Br3N)[SbCl6], (I), and neutral tris(4-bromophenyl)amine, C18H12Br3N, (II), show extremely similar three-bladed propeller structures with planar N atoms. Key geometric features, such as the C,N bond distances and the angles between the planes of the aryl groups and the central NC3 plane, are identical within experimental uncertainty in the two structures. This contrasts with the significant structural changes observed on oxidation of more electron-rich triarylamines, where resonance contributes to the stabilization of the radical cation, and suggests that, in general, more strongly oxidizing triarylaminium cations will have lower inner-sphere reorganization energies than their lower-potential analogues. [source] Hydrogen-bonding patterns in three substituted N -benzyl- N -(3- tert -butyl-1-phenyl-1H -pyrazol-5-yl)acetamidesACTA CRYSTALLOGRAPHICA SECTION C, Issue 4 2010Gerson López The molecules of N -(3- tert -butyl-1-phenyl-1H -pyrazol-5-yl)-2-chloro- N -(4-methoxybenzyl)acetamide, C23H26ClN3O2, are linked into a chain of edge-fused centrosymmetric rings by a combination of one C,H...O hydrogen bond and one C,H...,(arene) hydrogen bond. In N -(3- tert -butyl-1-phenyl-1H -pyrazol-5-yl)-2-chloro- N -(4-chlorobenzyl)acetamide, C22H23Cl2N3O, a combination of one C,H...O hydrogen bond and two C,H...,(arene) hydrogen bonds, which utilize different aryl rings as the acceptors, link the molecules into sheets. The molecules of S -[N -(3- tert -butyl-1-phenyl-1H -pyrazol-5-yl)- N -(4-methylbenzyl)carbamoyl]methyl O -ethyl carbonodithioate, C26H31N3O2S2, are also linked into sheets, now by a combination of two C,H...O hydrogen bonds, both of which utilize the amide O atom as the acceptor, and two C,H...,(arene) hydrogen bonds, which utilize different aryl groups as the acceptors. [source] Synthesis and Biological Evaluation of Some Polymethoxylated Fused Pyridine Ring Systems as Antitumor AgentsARCHIV DER PHARMAZIE, Issue 10 2009Sherif A. F. Rostom Abstract A series of 3,5- bis(arylidene)-4-piperidones like chalcone analogues carrying variety of methoxylated aryl groups, pyrazolo[4,3- c]pyridines, pyrido[4,3- d]pyrimidines, and pyrido[3,2- c]pyridines, carrying an arylidene moiety, and some pyrano[3,2- c]pyridines, like flavone and coumarin isosteres, were synthesized and screened for their in-vitro antitumor activity at the National Cancer Institute (NCI, USA). The tested compounds 7, 9, 10, 12, 13, 15, 17, and 19 exhibited a broad spectrum of antitumor activity. Compounds belonging to the pyrazolo[4,3- c]pyridine series proved to be more active than those of the pyrido[3,2- c]pyridine and pyrano[3,2- c]pyridine analogues, in which the monomethoxylated derivatives showed better antitumor activity when compared with their corresponding dimethoxylated congeners. Compound 7 is considered to be the most active member identified in this study with a broad spectrum of activity against 22 different tumor cell lines belonging to the nine subpanels employed, and a particular effectiveness against the breast cancer T-47D cell line (GI 54.7%). The pyrano[3,2- c]pyridine heterocyclic system 19 proved to be the most active antitumor agent among the six-membered fused pyridines, with variable activity against 18 different tumor cell lines, and special activity against the non-small cell lung cancer Hop-92 and ovarian cancer OVCAR-4 cell lines (GI values 63.9 and 48.5%, respectively). [source] New Chiral N-Heterocyclic Carbene Ligands in Palladium-Catalyzed ,-Arylations of Amides: Conformational Locking through Allylic Strain as a Device for StereocontrolCHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2010Yi-Xia Jia Dr. Abstract New Enders/Herrmann-type chiral N-heterocyclic carbene (NHC) ligands have been developed and applied in asymmetric palladium-catalyzed intramolecular ,-arylations of amides. The best ligands feature the bulky tert -butyl group and ortho -substituted aryl groups at the stereogenic centers. Aryl bromides readily react at room temperature and aryl chlorides at 50,°C. The highly enantiomerically enriched (up to 96,%,ee) 3-alkyl-3-aryloxindole products were obtained in generally high yields (>95,%) except in cases of steric congestion. The critical roles both of the bulky alkyl group and of the ortho -aryl substituent at the stereogenic center of the ligand were revealed in the crystal structure of a [Pd(,3 -allyl)(NHC-L*)(I)] complex. The ligand aryl location and orientation is fixed by conformational locking that minimizes A1,3 -strain and enables optimal transfer of chiral information. [source] Structural Diversity in the Self-Assembly of Pseudopeptidic MacrocyclesCHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2010Ignacio Alfonso Dr. Abstract The self-assembling abilities of several pseudopeptidic macrocycles have been thoroughly studied both in the solid (SEM, TEM, FTIR) and in solution (NMR, UV, CD, FTIR) states. Detailed microscopy revealed large differences in the morphology of the self-assembling micro/nanostructures depending on the macrocyclic chemical structures. Self-assembly was triggered by the presence of additional methylene groups or by changing from para to meta geometry of the aromatic phenylene backbone moiety. More interestingly, the nature of the side chain also plays a fundamental role in some of the obtained nanostructures, thus producing structures from long fibers to hollow spheres. These nanostructures were obtained in different solvents and on different surfaces, thus implying that the chemical information for the self-assembly is contained in the molecular structure. Dilution NMR studies (chemical shift and self-diffusion rates) suggest the formation of incipient aggregates in solution by a combination of hydrogen-bonding and ,,, interactions, thus implicating amide and aryl groups, respectively. Electronic spectroscopy further supports the ,,, interactions because the compounds that lead to fibers show large hypochromic shifts in the UV spectra. Moreover, the fiber-forming macrocycles also showed a more intense CD signature. The hydrogen-bonding interactions within the nanostructures were also characterized by attenuated total-reflectance FTIR spectroscopy, which allowed us to monitor the complete transition from the solution to the dried nanostructure. Overall, we concluded that the self-assembly of this family of pseudopeptidic macrocycles is dictated by a synergic action of hydrogen-bonding and ,,, interactions. The feasibility and geometrical disposition of these interactions finally render a hierarchical organization, which has been rationalized with a proposal of a model. The understanding of the process at the molecular level has allowed us to prepare hybrid soft materials. [source] Ultralong Carbon,Carbon Bonds in Dispirobis(10-methylacridan) Derivatives with an Acenaphthene, Pyracene, or Dihydropyracylene SkeletonCHEMISTRY - A EUROPEAN JOURNAL, Issue 19 2008Hidetoshi Kawai Dr. Abstract Acenapthalene, pyracene, and dihydropyracylene attached to two units of spiroacridan are a novel class of hexaphenylethane (HPE) derivatives that have an ultralong CC bond (1.77,1.70,Å). These sterically challenged molecules were cleanly prepared by CC bond formation through two-electron reduction from the less-hindered dications. These ultralong bonds were realized based on several molecular-design concepts including enhanced "front strain" through "multiclamping" by means of fusing or bridging aryl groups in the HPE molecule. The lengths of these ultralong bonds and their relation to the conformation (torsional angle) were also validated by means of theoretical calculations. Bond-fission experiments revealed that the bonds are more easily cleaved than standard covalent bonds to produce the corresponding dication upon oxidation with an increase in the length of the CC bond. [source] Synthesis, Structure and Emission Properties of Spirocyclic Benzofuranones and Dihydroindolones: A Domino Insertion,Coupling,Isomerization, Diels,Alder Approach to Rigid FluorophoresCHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2008Daniel Abstract An alkynoyl ortho -iodo phenolester or alkynoyl ortho -iodo anilides and propargyl allyl ethers react under Sonogashira coupling conditions in the sense of an insertion,coupling,isomerization,Diels,Alder hetero domino reaction to furnish (tetrahydroisobenzofuran)-spirobenzofuranones and -spirodihydroindolones in good yields. Many representatives can be crystallized and single crystal structure analyses display steric and electronic substituent effects on the torsional angles of the terminal (hetero)aryl groups and the central cis,trans -butadiene fragment. DFT computations reveal that in the final pericyclic step the Diels,Alder termination is by far thermodynamically and kinetically favored over a possible Claisen rearrangement. Compounds of this new class of spirocyclic compounds possess large Stokes shifts and fluoresce intensively with blue over green to orange colors. As a consequence of the spirocyclic rigidity fluorescence lifetimes and quantum yields are rather high in some cases. Alkinoyl ortho -iodphenolester oder Alkinoyl ortho -iodanilide und Propargylallylether reagieren unter den Bedingungen der Sonogashira-Kupplung im Sinne einer Insertions,Kupplungs,Diels,Alder-Hetero-Domino-Reaktion zu (Tetrahydroisobenzofuran)-spirobenzofuranonen bzw. -spirodihydroindolonen in guten Ausbeuten, von denen viele kristallisiert werden konnten. Die Einkristallstrukturanalysen offenbaren sterische und elektronische Substituenteneffekte auf die Torsionswinkel der terminalen (Hetero)arylgruppen und des zentralen cis,trans -Butadienfragments. DFT-Rechnungen zeigen, dass im letzten pericyclischen Schritt die Diels,Alder-Reaktion gegenüber einer möglichen Claisen-Umlagerung bei weitem thermodynamisch und kinetisch begünstigt ist. Viele Verbindungen dieser neuen Spirocyclenklasse besitzen große Stokes-Verschiebungen und fluoreszieren intensive mit blauer, grüner oder oranger Farbe. Als Folge der spirocyclischen Rigidität sind in einigen Fällen die Fluoreszenzlebensdauern und Quantenausbeuten relative hoch. [source] Structural Analysis of Chiral Complexes of Palladium(0) with 15-Membered Triolefinic Macrocyclic LigandsCHEMISTRY - A EUROPEAN JOURNAL, Issue 9 2005Anna Pla-Quintana Abstract The complete structural analysis of the palladium complexes of the triolefinic macrocycles (E,E,E)-1,6,11-tris(arylsulfonyl)-1,6,11-triazacyclopentadeca-3,8,13-trienes, which featured from three identical to three different aryl groups, was achieved by performing X-ray diffraction studies, NMR spectroscopy, and other calculations. The stereochemical complexity is determined by the different isomers formed through complexation of the metal to one or other face of each of the three olefins involved. The palladacyclopropane formulation of the palladium,olefin interaction offers a clear picture of the stereogenicity of the olefin carbon atoms that are complexed to the metal. The energetically favorable isomers were identified in the solid-state and in solution by performing X-ray diffraction and NMR spectroscopic analysis, respectively. Els complexos de pal,ladi de macrocicles triolefínics de tipus (E,E,E)-1,6,11-tris(arilsulfonil)-1,6,11-triazaciclopentadeca-3,8,13-triè, contenint des de tres unitats aríliques iguals fins a tres de diferents han estat estudiats mitjançant difracció de Raigs-X, espectroscòpia de RMN i càlculs teòrics. La complexitat estereoquímica deriva dels diferents isomers que es poden formar degut a la complexació del metall amb cadascuna de les dues cares de les tres olefines. La representació dels enllaços metall-olefina com a pal,ladaciclopropans permet una visualització més senzilla de l,estereoquímica dels àtoms de carboni olefínics després de la complexació. Els isomers energèticament possibles han estat determinats en l,estat sòlid i en solució mitjançant difracció de Raigs-X i espectroscòpia de RMN respectivament. [source] On the Tacticity of Polynorbornenes with 5,6- endo Pendant Groups That Contain Substituted Aryl ChromophoresCHEMISTRY - AN ASIAN JOURNAL, Issue 6 2007Wei-Yu Lin Abstract Two dimers and a series of polymers with 5,6- endo pendant aryl groups that contain different substituents at the para positions were synthesized. The conformation and stereochemistry of the dimers and polymers were determined by nonlinear optical analysis (EFISH) as well as UV/Vis and 13C,NMR spectroscopy. The chemical shifts of C7 for the polymers appeared as two peaks in the 13C,NMR spectra when the substituents are electron-withdrawing groups. The percentage decrease in the relative extinction coefficient of the polymers, ,d, was linearly related to the Hammett constant ,. Polynorbornenes with electron-withdrawing substituents may adopt isotactic stereochemistry with all pendant groups aligned in one direction. The nature of the interactions between neighboring chromophores may be one of the most important factors in directing the stereoregularity and conformation of these polymers. The corresponding polymers derived from the exo isomers appeared to be less stereoregular. [source] Design of Multivalent Galactoside Ligands and Their Binding to Hepatic Asialoglycoprotein ReceptorCHINESE JOURNAL OF CHEMISTRY, Issue 8 2006Xiao-Ru Zhang Abstract In an effort to find highly efficient ligands for hepatic asialoglycoprotein receptor (ASGPR), four cluster galactosides with different scaffolds were synthesized in this paper. The affinity of these compounds for ASGPR was analyzed by binding study invitro. The results showed that trivalent cluster galactosides behaved better than divalent analogues and the cluster galactosides with aryl groups on their scaffolds presented better binding affinity than those with aliphatic chain scaffolds. [source] | ||||||||||||||||||||||