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Chemical Transformation (chemical + transformation)
Selected AbstractsSynthesis, Structure and Chemical Transformations of EthynylgermatranesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2003Edmunds Lukevics Abstract Ethynylgermatranes have been prepared from monosubstituted acetylenes by a three-step synthesis without isolation of the hydrolytically unstable intermediate chlorogermanes and ethoxygermanes. Boiling an equimolar mixture of tetrachlorogermane Cl4Ge, acetylene RC,CH and triethylamine in hexane leads to germylation of the Csp,H bond and the formation of ethynyl-substituted trichlorogermanes. Subsequent alkoxylation of chlorogermanes by ethanol in the presence of triethylamine affords triethoxygermanes that then take part in transalkoxylation with triethanolamine to give ethynylgermatranes. The molecular structures of all ethynylgermatranes and the hexacarbonyldicobalt complex of 1-heptynylgermatrane have been determined by X-ray crystallography. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Synthesis and Some Chemical Transformations of (Z)- and (E)-2-Acetyl-1-ferrocenyl-3-methylbuta-1,3-dienes , A New Type of Cationic CycloadditionEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 8 2004Elena I. Klimova Abstract Dehydration of (E)- and (Z)-2-acetyl-1-ferrocenyl-3-methylbut-1-en-3-ols gave the corresponding (E)- and (Z)-2-acetyl-1-ferrocenyl-3-methylbuta-1,3-dienes, which have a cross-conjugated system of three double bonds. These heterotrienes readily afford the products of linear and cyclodimerization by following a cationic cyclodimerization mechanism; they also form Diels,Alder adducts with azodicarboxylic and maleic acid N -phenylimides. The spatial structures of (E)-2-acetyl-1-ferrocenyl-3-methylbuta-1,3-diene, (E,E)-1,5-diferrocenyl-2-isopropenyl-6-isopropylidene-3-methyl-1,3-octadiene-7-one, and 7-ferrocenyl-4-(ferrocenylmethylidene)-8-isopropylidene-1,3,5-trimethyl-9-oxabicyclo[3.3.1]non-2-ene were elucidated by X-ray diffraction analyses of single crystals. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Novel Chemical Transformations of TenoxicamHELVETICA CHIMICA ACTA, Issue 8 2005Kristóf Kóczián Both N - and O -substituted derivatives of the anti-inflammatory drug tenoxicam (=,4-hydroxy-2-methyl- N -(pyridin-2-yl)-2H -thieno[2,3 -e],[1,2]thiazine-3-carboxamide 1,1-dioxide; 1) were synthesized, and various chemical transformations were investigated. Both selective hydrolysis and reaction of 1,- N -methyltenoxicam (5) with a variety of N-nucleophiles were performed (Scheme,1). Also, five new 4- O -acyl derivatives 10 were prepared as potential prodrugs (Scheme,2). The 4-chloro derivatives of 1 and its analog 8 could be successfully transformed into the novel tetra- and tricyclic ring systems 12 and 13, respectively, the latter being a conformationally restricted 1,5-diaryl-pyrazole designed as a potential COX-2 inhibitor. [source] ChemInform Abstract: Synthesis and Some Chemical Transformations of N-Cyclohexyl-2-imino-4-methyl-5,5-pentamethylene-2,5-dihydrofuran-3-carb oxamide.CHEMINFORM, Issue 20 2010A. A. Avetisyan Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 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] Synthesis and Chemical Transformations of Partially Hydrogenated [1,2,4]Triazolo[5,1-b]quinazolines.CHEMINFORM, Issue 48 2006V. V. Lipson 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] Hetarynic Synthesis and Chemical Transformations of Dihydrodiquinolinopyrazines.CHEMINFORM, Issue 5 2005Irina-Claudia Grig-Alexa Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Spirocyclopropanated Bicyclopropylidenes: Straightforward Preparation, Physical Properties, and Chemical Transformations.CHEMINFORM, Issue 5 2002Armin de Meijere Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 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] Metabolism versus chemical transformation or pro- versus prehaptens?CONTACT DERMATITIS, Issue 2 2006Jean-Pierre Lepoittevin No abstract is available for this article. [source] Vertical Nanostructures: Vertical (La,Sr)MnO3 Nanorods from Track-Etched Polymers Directly Buffering Substrates (Adv. Funct.ADVANCED FUNCTIONAL MATERIALS, Issue 6 2010Mater. The inside cover image shows a tilted SEMFE image of La0.7Sr0.3MnO3 vertical nanorods. A. Carretero-Genevrier and co-workers have established a new method to generate vertical complex oxides nanostructures based on a sol,gel precursor solution and using track-etched polymers that act to buffer the substrate, which is described on page 892. These vertical nanorods grown at mild temperature undergo a complete structural, morphological, and chemical transformation into single crystalline (LaSr)xOy nanopyramids upon thermal activation at 1000°C. [source] Topotactic Conversion Route to Mesoporous Quasi-Single-Crystalline Co3O4 Nanobelts with Optimizable Electrochemical PerformanceADVANCED FUNCTIONAL MATERIALS, Issue 4 2010Li Tian Abstract The growth of mesoporous quasi-single-crystalline Co3O4 nanobelts by topotactic chemical transformation from , -Co(OH)2 nanobelts is realized. During the topotactic transformation process, the primary , -Co(OH)2 nanobelt frameworks can be preserved. The phases, crystal structures, morphologies, and growth behavior of both the precursory and resultant products are characterized by powder X-ray diffraction (XRD), electron microscopy,scanning electron (SEM) and transmission electron (TEM) microscopy, and selected area electron diffraction (SAED). Detailed investigation of the formation mechanism of the porous Co3O4 nanobelts indicates topotactic nucleation and oriented growth of textured spinel Co3O4 nanowalls (nanoparticles) inside the nanobelts. Co3O4 nanocrystals prefer [0001] epitaxial growth direction of hexagonal , -Co(OH)2 nanobelts due to the structural matching of [0001] , -Co(OH)2//[111] Co3O4. The surface-areas and pore sizes of the spinel Co3O4 products can be tuned through heat treatment of , -Co(OH)2 precursors at different temperatures. The galvanostatic cycling measurement of the Co3O4 products indicates that their charge,discharge performance can be optimized. In the voltage range of 0.0,3.0,V versus Li+/Li at 40,mA g,1, reversible capacities of a sample consisting of mesoporous quasi-single-crystalline Co3O4 nanobelts can reach up to 1400,mA h g,1, much larger than the theoretical capacity of bulk Co3O4 (892,mA h g,1). [source] Dual-Tone Patterned Mesoporous Silicate Films Templated From Chemically Amplified Block CopolymersADVANCED FUNCTIONAL MATERIALS, Issue 17 2009Sivakumar Nagarajan Abstract Directly patterned mesoporous silicate films are prepared using positive- and negative-tone strategies by performing phase selective silica condensation within lithographically exposed poly(styrene- b - tert -butyl acrylate) (PS- b -PtbA) templates containing photoacid generators. The use of supercritical fluid as a process medium enables rapid diffusion of the silicate precursor within the prepatterned block copolymer template film without disrupting its morphology. Template exposure through the mask triggers area selective generation of acid, which in turn both deprotects the poly(tert -butyl acrylate) block to yield a poly(acrylic acid) block and provides a catalyst for silica precursor condensation yielding pattern formation at the device level. Because the acid generated in the UV exposed field preferentially segregates into hydrophilic poly(acrylic acid) domains of the phase segregated, deprotected block copolymer, precursor condensation is simultaneously controlled at nanoscopic length scales via templating by the underlying block copolymer morphology. The ability of PS- b -PtbA to undergo chemical transformation in two stages, deprotection followed by crosslinking, enables precise replications of the photomask in positive and negative tones. Detemplating via calcination yields patterned mesoporous silicate films without etching. Template formulations are optimized using infrared spectroscopic studies and the silicate films are characterized using electron microscopy and scanning force microscopy. [source] Biological energy requirements as quantitative boundary conditions for life in the subsurfaceGEOBIOLOGY, Issue 4 2004T. M. HOEHLER ABSTRACT All life requires energy, which must be extracted from the environment. For all known life, free energy must be available at finite minimum levels in order to be usefully harnessed and must be delivered at finite minimum rates in order to support basic biochemical integrity and function. While seldom tested in the high energy light- and oxygen-based metabolisms of the surface biosphere, the magnitude of these requirements , the biological energy quantum (BEQ) and maintenance energy (ME) requirements, respectively , is considerable with respect to the potential metabolisms and energy sources that characterize the deep subsurface realm. As such, they constitute a fundamental constraint on the possible nature, distribution, and activity of microbial life in that environment. Because the energy released in a chemical transformation can be equated to the concentrations of substrates and products, both the BEQ and ME requirements define the minimum substrate concentration and minimum substrate production rate that must be sustained by a given environment for it to be capable of supporting life. The magnitudes of the BEQ and ME requirements are sensitive to a range of environmental parameters that may vary significantly in the subsurface. Temperature exerts a particularly strong control and is among the most important parameters to be considered in evaluating the energetic habitability of subsurface environments. [source] Triumfettamide and Triumfettoside Ic, Two Ceramides and Other Secondary Metabolites from the Stems of Wild Triumfetta cordifoliaA.HELVETICA CHIMICA ACTA, Issue 7 2008Rich. (Tiliaceae) Abstract Two new ceramides, triumfettamide (1) and triumfettoside Ic (2), characterized as (2R,6Z)-2-hydroxy- N -[(2S,3S,4R)-1,3,4-trihydroxyhexacosan-2-yl]heptadec-6-enamide and (2R)- N -{(1S,2R,3E,6Z, 9Z,12Z,15Z)-1-[(, - D -glucopyranosyloxy)methyl]-2-hydroxyheneicosa-3,6,9,12,15-pentaen-1-yl}-2-hydroxytetradecanamide, respectively, were isolated from the stems of Triumfetta cordifoliaA. Rich. besides eight known secondary metabolites identified as heptadecanoic acid, , -sitosterol glucopyranoside, friedelin, lupeol, betulin, maslinic acid, 2-hydroxyoleanolic acid and the mixture of stigmasterol and , -sitosterol. Their structures were determined on the basis of spectroscopic methods as well as HR-MALDI-FT-ICR-MS analysis, chemical transformation, and by comparison of their physical and spectral data with those reported in the literature and with authentic specimens for some known compounds. Five pentacyclic triterpenoids, friedelin, lupeol, betulin, maslinic acid, and 2-hydroxyoleanolic acid, have been isolated from Triumfetta genus for the first time. [source] Chemical Constituents of Polyalthia nemoralisHELVETICA CHIMICA ACTA, Issue 4 2007Xiu-Feng He Abstract Three new natural products, the taraxastane-type triterpenoid 1, the azafluorene-based constituent 2-hydroxyonychine (2), and the diterpenoid nemoralisin (3) were isolated from the EtOH extract of Polyalthia nemoralis, along with five known compounds. The structures of the new compounds were established by in-depth spectroscopic and mass-spectrometric analyses, as well as by chemical transformation. [source] Lycodine-Type Alkaloids from Lycopodium casuarinoidesHELVETICA CHIMICA ACTA, Issue 1 2006Sheng Yin Abstract Two new lycodine-type alkaloids, huperzinine N -oxide (1) and 8,15-dihydrohuperzinine (2) as well as five known compounds, huperzinine (3), huperzine B (4), huperzine D (5), N -demethylhuperzinine (6), and , -obscurine (7), were isolated from the club moss Lycopodium casuarinoides. The structures of 1 and 2 were elucidated by spectroscopic methods and chemical transformation. The absolute configuration of 1 was established by chemical correlation with 3, and that of 2 was determined by its CD spectrum. [source] Two New and a Known Compound from Lawsonia inermisHELVETICA CHIMICA ACTA, Issue 6 2003A new obtusafuran derivative, lawsonicin (1), and a new naphthaquinone, lawsonadeem (2), along with a known constituent, vomifoliol (3), were isolated from the aerial parts of Lawsonia alba and characterized by chemical transformation and spectroscopic experiments, including 2D-NMR techniques. [source] Novel routes to aminophosphonic acids: Interaction of dimethyl H-phosphonate with hydroxyalkyl carbamatesHETEROATOM CHEMISTRY, Issue 2 2008K. Troev It was found that the reaction of dimethyl H-phosphonate (1) with 2-hydroxyalkyl- N -2,-hydroxyalkyl carbamates at 135°C includes several chemical reaction steps: (i) chemical transformations of 1-methyl-2-hydroxyethyl- N -2,-hydroxyethyl carbamate (2) and 2-methyl-2-hydroxyethyl- N -2,-hydroxyethyl carbamate (3); (ii) transesterification of dimethyl H -phosphonate with 2 and 3, and with secondary hydroxyl-containing compounds that are formed during the course of the chemical transformation of 2-hydroxyalkyl- N -2,-hydroxyalkyl carbamates; (iii) hydrolysis of 1 and dialkyl H-phosphonates, formed via transesterification of 1 with secondary hydroxyl-containing compounds. The interaction was studied by means of 1H, 13C, 31P NMR, and FAB mass spectroscopy. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:119,124, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20404 [source] A Microfluidic Approach to the Rapid Screening of Palladium-Catalysed Aminocarbonylation ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Philip Abstract The evaluation and selection of the most appropriate catalyst for a chemical transformation is an important process in many areas of synthetic chemistry. Conventional catalyst screening involving batch reactor systems can be both time-consuming and expensive, resulting in a large number of individual chemical reactions. Continuous flow microfluidic reactors are increasingly viewed as a powerful alternative format for reacting and processing larger numbers of small-scale reactions in a rapid, more controlled and safer fashion. In this study we demonstrate the use of a planar glass microfluidic reactor for performing the three-component palladium-catalysed aminocarbonylation reaction of iodobenzene, benzylamine and carbon monoxide to form N -benzylbenzamide, and screen a series of palladium catalysts over a range of temperatures. N -Benzylbenzamide product yields for this reaction were found to be highly dependent on the nature of the catalyst and reaction temperature. The majority of catalysts gave good to high yields under typical flow conditions at high temperatures (150,°C), however the palladium(II) chloride-Xantphos complex [PdCl2(Xantphos)] proved to be far superior as a catalyst at lower temperatures (75,120,°C). The utilised method was found to be an efficent and reliable way for screening a large number of palladium-catalysed carbonylation reactions and may prove useful in screening other gas/liquid phase reactions. [source] New routes to steroidal heterocyclic derivatives: Synthesis of biologically active pyrazolyl- and isoxazolylpregnene derivativesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 1 2007Abdou O. Abdelhamid Pyrazolyl- and isoxazolylpregnene derivatives were synthesized from the appropriate hydrazonoyl chlorides and hydroximoyl chlorides with enaminoprogesterone derivative. The newly synthesized compounds were elucidated by elemental analysis, spectral data and chemical transformation. Some products were tested towards some bacteria and some Fungal-plant pathogens [source] Synthesis and chemical transformation of fused tetrazoles derived from 2-bromomethyl- and 2-iodomethyl-3,5,6,7-tetrahydro-4(2H)-benzofuranonesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 4 2006Malose J. Mphahlele The 2-bromomethyl-3,5,6,7-tetrahydrobenzofuranones 1a-d were subjected to triazidochlorosilanesodium azide-mediated Schmidt rearrangement to afford the corresponding tetrazolofuroazepine derivatives 2a-dvia methylene shift. Under similar reaction conditions, the 2-iodomethyl-3,5,6,7-tetrahydrobenzofuranones 1e-h afford mixtures of the corresponding tetrazolofuroazepines 2e-h and the 4-azido-2-iodomethyl-2,3-dihydrobenzofuran derivatives 3a-c. A mechanism is proposed to account for the divergence in the reactivity of these 2-halogenomethyltetrahydrobenzofuranones (X = Br versus I). In turn, the 2-halogenomethyltetrazolofuroazepines 2a,b,d-h and the 4-azido-2-iodomethyl-2,3-dihydrobenzofurans 3a,b underwent nucleophilic substitution with triethyl phosphite and dehydrohalogenation using DBU in refluxing toluene to give the corresponding tetrazolofuroazepines 4a-d and 5a-c and benzofurans 6a,b. [source] Synthesis and further studies of chemical transformation of the 2-aryl-3-halogenoquinolin-4(1H)-one derivativesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 2 2006Malose J. Mphahlele The C-3 brominated and iodinated derivatives were prepared from the corresponding 2-arylquinolin-4(1H)-ones and their NMe-4-oxo derivatives using pyridinium tribromide in acetic acid or iodine-Na2CO3 mixture in THF. The results of further studies of chemical transformation of the prepared ,-haloenones and preliminary antitumour activity of the 3-bromo NH-4-oxo and NMe-4-oxo derivatives are also described. [source] Preferential flow and aging of NAPL in the unsaturated soil zone of a hazardous waste site: implications for contaminant transportJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 1 2003Kai U. Totsche Abstract Flow of non-aqueous phase liquids (NAPL) in the unsaturated zone is thought to be driven by gravity with a dominant vertical flow direction, and lateral spreading to be limited to the gradient of the relative permeabilities. The effect of soil profile build-up, preferential flow, aging, and groundwater level fluctuations is mostly neglected. The objective of our study was to check the effects of such processes on the fate of NAPL in the unsaturated soil zone. At a hazardous waste site, we conducted a field survey of the unsaturated soil zone and monitored the groundwater for a two year period. We conducted spatially resolved and depth dependent soil sampling and analysis and the evaluation of former ram and core drilling protocols. The samples were analyzed for the 16 EPA PAH and alkanes with GC-MS and GC-FID. 13C-NMR spectroscopy was used to assess structural changes of the NAPL phase. Flow of bulk NAPL along macropores and along preferential permeability structures, like sedimentation discontinuities, are the dominant transport pathways which cause large lateral spreading beyond those expected by the relative permeability gradient. Accumulation of NAPL was found at locations with abrupt textural changes and within the zone of capillary rise. Aging of NAPL results in the depletion in soluble and volatile compounds but also in oxidation and polymerization. It increases the chemical diversity and decreases the mobility of the NAPL. Thus, NAPL flow ceases much earlier than expected from the capillary forces. As chemical transformation is restricted to the NAPL water/air interface, a skin-like thin film is formed which encapsulates and preserves the bulk NAPL from further hardening, limiting contaminant mass transfer from the NAPL to the aqueous phase. Präferenzieller Fluss und Alterung nichtwässriger flüssiger Phasen (NAPL) in der ungesättigten Bodenzone eines Altlastenstandortes: Bedeutung für den Stofftransport Bei der Abschätzung der Tiefenverlagerung von nichtwässrigen Phasen (NAPL) in der ungesättigten Bodenzone ging man bisher davon aus, dass der Fluss im Boden eine dominante vertikale Fließkomponente besitzt. Die Bedeutung bevorzugter Fließwege, des Bodenprofils und der Alterung für die Ausbreitung der NAPL wurde bisher nicht untersucht. Ziel unserer Arbeiten war es daher, die Gültigkeit der Vorstellungen zum Transport von NAPL in der ungesättigten Bodenzone zu überprüfen. Hierzu wurde die ungesättigte Bodenzone an einem ehemaligen Teerwerkstandort untersucht und ein zweijähriges Grundwassermonitoring durchgeführt. Es wurde eine tiefendifferenzierte und räumlich aufgelöste Probenahme mit Rammkernsondierungen und Linern durchgeführt, sowie Bohrprotokolle vorhandener Gutachten ausgewertet. In den Proben wurden Alkane mittels GC-FID und PAK mittels GC-MS bestimmt. NAPL wurden 13C-NMR-spektroskopisch untersucht. Der Fluss von NAPL entlang präferenzieller Fließpfade ist der dominante Prozess der Tiefenverlagerung. Dabei kommt es zu einer starken lateralen Ausbreitung von NAPL weit über den Bereich hinaus, der aufgrund der heterogenen Verteilung der relativen Permeabilitäten erwartet werden würde. Innerhalb des Bodenprofils reichern sich NAPL oberhalb der Grenzflächen mit abruptem Texturwechsel und innerhalb der kapillaren Aufstiegszone an. Alterung der NAPL führt zu einer Zunahme der chemischen Diversität und zu einer Abnahme der Mobilität. Die Tiefenverlagerung von NAPL kommt viel früher zum Erliegen als durch Viskosität und Kapillarkräfte zu erwarten wäre. Die strukturchemischen Veränderungen beschränken sich jedoch auf die Grenzfläche NAPL/Wasser bzw. NAPL/Bodenluft: Es bildet sich eine dünne, verhärtete Grenzschicht aus, die die NAPL umhüllt, die weitere Alterung verlangsamt und den Stoffaustausch zwischen NAPL und Bodenwasser bzw. der Bodenluft verringert. [source] Raman spectroscopy of conducting poly (methyl methacrylate)/polyaniline dodecylbenzenesulfonate blendsJOURNAL OF RAMAN SPECTROSCOPY, Issue 2 2010Abdul Shakoor Abstract Polyaniline soluble in organic solvents was prepared using dodecylbenzenesulphonic acid (DBSA) as functional dopant. The solubility parameter was calculated and the most suitable solvent chloroform was checked for the solubility and the most compatible polymer PMMA was selected for blending. Miscibility was maximized with 1% by weight of hydroquinone. Blending of doped polyaniline with dodecylbenzenesulphonic acid (PAni.DBSA) in poly (methyl methacrylate) (PMMA) was explained by a change in the conformation of the polymeric chains leading to an increase in the conductivity. The electrical conductivity increased as the weight percent of PAni.DBSA increased, showing a percolation threshold as low as 3.0% by weight and the highest conductivity was achieved at 20% by wt of PAni.DBSA. Scanning electron micrographs showed lowest level of phase separation. Raman spectroscopy is used to characterize the blending process of two polymers aiming to understand the transformations in different types of charged segments. Raman results give complementary data about the blending process showing that together with the structural change of the polymeric chains, there is also a chemical transformation of these polymers. Analysis of Raman spectra was done investigating the relative intensities of the bands at 574 cm,1 and 607 cm,1. A relationship between conductivity and Raman was also proposed. Copyright © 2009 John Wiley & Sons, Ltd. [source] "Click" Dielectrics: Use of 1,3-Dipolar Cycloadditions to Generate Diverse Core-Shell Nanoparticle Structures with Applications to Flexible ElectronicsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 18 2008Meghann A. White Abstract We have synthesized a "universal ligand" incorporating a phosphonate surface anchor and a terminal alkyne moiety which binds to TiO2 nanoparticles and exhibits excellent dispersity in organic solvents. The alkyne functionality permits attachment of azide terminated polymer shells using "click" chemistry. Thus TiO2 core nanoparticles have been encapsulated with both polystyrene and poly(t -butyl acrylate) shells. The TiO2 -poly(t -butyl acrylate) core shell nanoparticles are amenable to further chemical transformation into TiO2 -poly(acrylic acid) nanoparticles through ester hydrolysis. These TiO2 -polyacrylic acid nanoparticles are dispersible in aqueous solution. The resulting core-shell nanoparticles have been incorporated as high K dielectric films in capacitor and organic thin film transistor devices and are promising new materials for flexible electronics applications. [source] Synthesis of Symmetrical Multichromophoric Bodipy Dyes and Their Facile Transformation into Energy Transfer Cassettes,CHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2010Altan Bozdemir Dr. Abstract Multichromophoric boron-dipyrromethene (Bodipy) dyes synthesized on phenylene-ethynylene platforms have been be converted to energy transfer cassettes in a one-step chemical transformation. Excitation energy transfer processes in these highly symmetrical derivatives were studied in detail, including time-resolved fluorescence spectroscopy techniques. Excitation spectra and the emission lifetimes suggest efficient energy transfer between the donor and acceptor chromophore. These novel energy transfer cassettes, while highlighting a short-cut approach to similar energy transfer systems, could be useful as large pseudo-Stokes shift multichromophoric dyes with potential applications in diverse applications. Fenilenetilen platformu üzerinde sentezlenen multikromoforik Bodipy boyarmaddeleri, tek basamakl, bir kimyasal transformasyonla enerji transferi kasetlerine dönü,türülmü,tür. Zaman ayr,ml, floresans spektroskopisi tekniklerinin de içinde bulundu,u yöntemlerle, yüksek simetri ö,eleri bulunduran bu türevlerdeki eksitasyon enerjisi transferi süreçleri ayr,nt,l, olarak çal,,,lm,,t,r. Eksitasyon spektrumlar, ve emisyon ömürlerindeki de,i,im, donör ve akseptör kromoforlar, aras,nda etkin bir enerji transferi oldu,unu dü,ündürmektedir. Bu yeni enerji transfer kasetleri, benzer enerji transfer sistemlerine kolay bir geçi, yolu göstermekle birlikte, pek çok farkl, alanda potansiyel uygulamalar, olabilecek, büyük pseudo-Stokes kaymas, de,erlerine sahip multikromoforik boyarmaddeler olarak da yararl, olabilirler. [source] Enantioselective Synthesis of Non-Natural Aromatic ,-Amino AcidsCHEMISTRY - A EUROPEAN JOURNAL, Issue 2 2004Andreas Krebs Abstract We present two complementary methods for the stereoselective synthesis of non-natural ,-amino acids with aromatic or heteroaromatic side chains. One approach is based on the chemical transformation of methionine, whereas the other applies the stereoselective Myers alkylation of glycine. The resulting product types differ in the linker length between glycine and the aromatic substituent. Since methionine and pseudoephedrine are available in both absolute configurations, R - or S -configured enantiopure amino acids with either C2 or C3 linkers can be obtained on gram scales. In each case the key step of the synthesis is hydroboration of the unsaturated building blocks 9 and 17, followed by palladium-catalyzed Suzuki cross-coupling with aryl halides. Attention must in certain cases be paid to the stereochemical integrity when basic Suzuki conditions are applied. Our initial difficulties are reported as well as the final "racemization-proof" procedures. The protecting groups chosen for the ,-amino acids should be compatible with solid-phase peptide synthesis. This was confirmed by the successful synthesis of a series of tripeptides. [source] Labdane Diterpenoid Glycosides from Aster veitchianusCHEMISTRY & BIODIVERSITY, Issue 3 2007Er-Wei Li Abstract Four new labdane-type rhamnopyranosides derived from 13-epimanool, compounds 1,4, with differently acetylated sugar moieties, were isolated from A. veitchianus. Their structures and absolute configurations were elucidated by chemical transformation, spectroscopic and mass-spectrometric analyses (IR, 1D- and 2D-NMR, HR-ESI-MS), as well as by single-crystal X-ray diffraction (compound 1). The isolates 2,4 were investigated for their cytotoxic properties against cultured human hepatoma (SMMC-7721), ovarian neoplasm (HO-8910), and leukemia (HL-60) cells, and for their antibacterial activities against Escherichia coli, Bacillus subtilis, and Staphylococcus aureus. [source] Novel Chemical Transformations of TenoxicamHELVETICA CHIMICA ACTA, Issue 8 2005Kristóf Kóczián Both N - and O -substituted derivatives of the anti-inflammatory drug tenoxicam (=,4-hydroxy-2-methyl- N -(pyridin-2-yl)-2H -thieno[2,3 -e],[1,2]thiazine-3-carboxamide 1,1-dioxide; 1) were synthesized, and various chemical transformations were investigated. Both selective hydrolysis and reaction of 1,- N -methyltenoxicam (5) with a variety of N-nucleophiles were performed (Scheme,1). Also, five new 4- O -acyl derivatives 10 were prepared as potential prodrugs (Scheme,2). The 4-chloro derivatives of 1 and its analog 8 could be successfully transformed into the novel tetra- and tricyclic ring systems 12 and 13, respectively, the latter being a conformationally restricted 1,5-diaryl-pyrazole designed as a potential COX-2 inhibitor. [source] Novel routes to aminophosphonic acids: Interaction of dimethyl H-phosphonate with hydroxyalkyl carbamatesHETEROATOM CHEMISTRY, Issue 2 2008K. Troev It was found that the reaction of dimethyl H-phosphonate (1) with 2-hydroxyalkyl- N -2,-hydroxyalkyl carbamates at 135°C includes several chemical reaction steps: (i) chemical transformations of 1-methyl-2-hydroxyethyl- N -2,-hydroxyethyl carbamate (2) and 2-methyl-2-hydroxyethyl- N -2,-hydroxyethyl carbamate (3); (ii) transesterification of dimethyl H -phosphonate with 2 and 3, and with secondary hydroxyl-containing compounds that are formed during the course of the chemical transformation of 2-hydroxyalkyl- N -2,-hydroxyalkyl carbamates; (iii) hydrolysis of 1 and dialkyl H-phosphonates, formed via transesterification of 1 with secondary hydroxyl-containing compounds. The interaction was studied by means of 1H, 13C, 31P NMR, and FAB mass spectroscopy. © 2008 Wiley Periodicals, Inc. Heteroatom Chem 19:119,124, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20404 [source] Reaction with hydrazonoyl halides.HETEROATOM CHEMISTRY, Issue 6 20013-dihydro-, 4-thiadiazoles, Part 32 [1]: Reaction of C -acyl- N -(3-phenyl-5-pyrazolyl)hydrazonoyl chlorides with potassium thiocyanate, slenadiazoles, synthesis of some new C-acyl-N-(3-phenyl-5-pyrazolyl)hydrazonoyl chlorides 1a,b react with potassium thiocyanate and potassium selenocyanate to give 5-acyl-2,3-dihydro-2-imino-3-(3,-phenyl)pyrazol-5,-yl)-1,3,4-thiadiazoles 2a,b and 5-acetyl-2,3-dihydro;-2-imino-3-(3,-phenyl)pyrazol-5,-yl)-1,3,4-selenadiazole 10a,b. Also, 2-[mercapto-(methylthio)methylene]indan-1,3-dione 16 reacts with hydrazonoyl halides 15 and 22,25 to afford 2,3-dihydro-1,3,4-thiadiazoles 19 and 26,29, respectively. Structures of the newly synthesized compounds are elucidated on the basis of spectral data, chemical transformations, and alternative synthesis methods. © 2001 John Wiley & Sons, Inc. Heteroatom Chem 12:468,474, 2001 [source] | ||||||||||||||||||||||||||||||||||