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Ring-opening Reaction (ring-opening + reaction)
Selected AbstractsRing-Opening Reaction of Cyclopropanated [60]Fullerenes: Unexpected Transformation of Methano[60]fullerenes Having an Electron-Donating Group on the Methano-Bridge Carbon.CHEMINFORM, Issue 39 2007Tomoyuki Tada 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] Ring-Opening Reactions of Methylenecyclopropanes with Diphenyl Diselenide upon Heating; Formation of 3-Phenylselenyl-2,5-dihydrofuran Derivatives.CHEMINFORM, Issue 18 2005Le-Ping Liu Abstract For Abstract see ChemInform Abstract in Full Text. [source] Ring-Opening Reactions of Iminosugar-Derived Aziridines: Application to the General Synthesis of ,-1-C-Substituted Derivatives of Fagomine.CHEMINFORM, Issue 43 2003Jean-Yves Goujon Abstract For Abstract see ChemInform Abstract in Full Text. [source] Synthesis of nitrogen-containing heterocycles 9,.JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 6 2000- a][, Preparation, ]-triazolo[, ]triazine] derivatives, carbon-carbon bond cleavage of spiro[cycloalkane[, related compounds Diaminomethylenehydrazones of cyclic ketones 1,5 reacted with ethyl N -cyanoimidate (I) at room temperature or with bis(methylthio)methylenecyanamide (II) under brief heating to give directly the corresponding spiro[cycloalkane[1,,2,,4,]triazolo[1,,5,,- a][1,,3,-5,]triazine] derivatives 7,12 in moderate to high yields. Ring-opening reaction of the spiro[cycloalkanetriazolotriazine] derivatives occurred at the cycloalkane moiety upon heating in solution to give 2-alkyl-5-amino[1,2,4]triazolotriazines 13,16. Diaminomethylenehydrazones 17,19, of hindered acyclic ketones, gave 2-methyl-7-methylthio[1,2,4]-triazolo[1,5- a][1,3,5]triazines 21,23 by the reaction with II as the main products with apparent loss of 2-methylpropane from the potential precursor, 2- tert -butyl-2-methyl-7-methylthio[1,2,4]triazolo[1,5- a]-[1,3,5]triazines 20, in good yields. In general, bis(methylthio)methylenecyanamide II was found to be a favorable reagent to the one-step synthesis of the spiro[cycloalkanetriazolotriazine] derivatives from the diaminomethylenehydrazones. The spectral data and structural assignments of the fused triazine products are discussed. [source] Ring-opening reactions of 5-(aryl)thianthrenium bromides with aryl thiolatesJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 3 2002Ding-Quan Qian Abstract A series of 5-(aryl)thianthrenium bromides (6a,e) with aryl (Ar) groups phenyl (a), p -tolyl (b), p -anisyl (c), p -chlorophenyl (d) and p -bromophenyl (e) was prepared by reaction of thianthrene 5-oxide with the appropriate Grignard reagent ArMgBr. Reactions of 6a,e with aryl thiolates (Ar,SNa, Ar,,=,phenyl, p -tolyl and p -chlorophenyl, 7a,c) were carried out in MeCN at room temperature. Products from 6a,c were a small amount of arene [benzene (8a) and toluene (8b)], and substantial amounts of ArSAr, (9), thianthrene (Th) and a trisulfide, namely a 2-(ArS)-2,-(Ar,S)-diphenyl sulfide (10). Products from reactions of 6d,e were smaller amounts of 9 and 10 but substantial amounts of 1,4-di(Ar,S)benzene (11) and a tetrasulfide (12a,c). The reactions that lead to products 9,12 are attributed to ligand coupling (LC) pathways in sulfuranes formed by attack of Ar,S, at the sulfonium S atom of 6. In the formation of 11 and 12 the halogen atom (Cl, Br) is first displaced from 6d,e by Ar,S,, giving a new thianthrenium ion (14) from which sulfurane formation (15) follows. Products 10 and 12 result from opening of the thianthrenium ring of sulfuranes 13 and 15 through LC. Products were assayed with a combination of GC and isolation with TLC, and were identified with a combination of GC (authentic compounds), x-ray crystallography (10a), elemental analyses and high-resolution mass spectrometry. The reactions of 6 are compared with earlier reactions of 5-(alkoxy)-and 5-(alkyl)thianthrenium salts (1 and 2). Copyright © 2002 John Wiley & Sons, Ltd. [source] Unusual cationic ring-opening behavior of a novel six-membered ring spiro-orthocarbonate bearing adamantane backbonesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2004Tetsuo Hino Ring-opening reactions of novel six-membered ring spiro-orthocarbonate bearing adamantane backbones 1 were investigated with several cationic initiators. As a result, the decarboxylative product, polyether 4 along with or without cyclic carbonate 3 were unusually formed instead of the anticipated poly(ether-carbonate) 2. The present unexpected reaction behavior can be explained to proceed via predominantly decomposition of starting monomer 1 to cyclic carbonate 3 and oxetane derivative 11 at the initial stage. [source] Switchable Fluorescent and Solvatochromic Molecular Probes Based on 4-Amino- N -methylphthalimide and a Photochromic DiaryletheneEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 15 2008Sergey F. Yan Abstract New fluorescent photochromic compounds (1 -H and 1 -Boc) have been synthesized and characterized in different solvents. The fluorescence emission can be switched "on" and "off" with visible light and UV, respectively, by means of the photochromic reaction. The emission wavelength and efficiency strongly depend on the polarity of the solvent. The compounds show a positive solvatochromic effect in the emission maxima, and their fluorescence quantum yield decreases as the solvent's polarity increases (from cyclohexane to dioxane). In solvents more polar than dioxane the emission is too weak and therefore undetectable, and thus 1 -H and 1 -Boc behave as "normal" photochromic compounds. The photochromic reaction is also sensitive to the environment. A decrease of more than an order of magnitude was found for the quantum yield of the colouring reaction (,OF,CF) for 1 -H in ethanol compared with cyclohexane, and an about threefold decrease in ,OF,CF was observed for the compound 1 -Boc in polar solvents (compared with apolar solvents). For both compounds the ring-opening reaction was found not to dependent on the solvent. The novel fluorescent molecular switches 1 -H and 1 -Boc are able to probe the polarity of their microenvironment. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [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] Integration of Solventless Reaction in a Multi-Step Process: Application to an Efficient Synthesis of PA-824ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2007Akihiro Orita Abstract In order to improve redundant synthetic processes, the integration of a solventless reaction has proved to be useful for gaining high reaction mass efficiency (RME) as well as reducing the amount of solvents. This concept was applied to synthesis of PA-824, a potential antituberculosis drug. Thus, the solventless ring-opening reaction of glycidyl silyl ether with dinitroimidazole was connected to succeeding solution reactions. The ring-opening of glycidol followed by selective silylation of the primary hydroxy group under solventless conditions was also feasible. As a consequence, the overall yield of the target compound was nearly tripled, and thus the RME values were increased more than 2.5 times while the amount of necessary solvents was decreased to less than 1/3. [source] Gold(I)- and Brønsted Acid-Catalyzed Ring-Opening of Unactivated Vinylcyclopropanes with SulfonamidesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2007Wen-Jian Shi Abstract The gold(I)- or Brønsted acid-catalyzed reaction of unactivated vinylcyclopropanes (VCPs) with sulfonamides affords useful homoallylic amine derivatives. This ring-opening reaction occurs in a highly selective manner affording in the case of ,-phenyl-substituted VCPs products with the E -configuration exclusively. [source] Synthesis of a new photoreactive gelatin with BTDA and HEMA derivativesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2008Fan-Chun Ding Abstract A novel bio-affinitive, photocuring, and membrane-forming gelatin derivative was synthesized in this study. This process was based on the amide formation between carboxylic acid and the amine in methanol,water media using dicyclohexyl-carbodiimide (DCC) as a condenser. Gelatin and glycine were the sources of amine in the model reaction. Since there were two anhydride groups in each 3,3,,4,4,-benzophenone tetra-carboxylic dianhydride (BTDA) molecule, two 2-hydroxyethyl methacrylate (HEMA) molecules were used to induce the ring-opening reaction of BTDA and release two carboxylic acid groups. The resulting photoreactive gelatin was called GE-BTHE, of which the photoreactive component was the ketone groups of BTDA and HEMA that played the role of double bond supplier. This photoreactive gelatin could be converted from the transparent liquid phase into swollen membrane by a 6-min irradiation of high pressure mercury lamp. The most efficient irradiation was at 267 nm and the highest degree of swelling of the cured GE-BTHE membrane could reach 5.9. The elongation from the dried gel remained 5,10%, i.e., relatively elastic. The properties of this gelatin derivative were investigated using amide formation analysis, calculation of the gel content and the swelling ratio, and monitoring of the photocuring process. The GE-BTHE synthesized in this study should be very potential in applications such as protective wound dressings and hemostatic absorbents for minimally invasive surgery. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] New type of phenolic resin,The curing reaction of bisphenol A based benzoxazine with bisoxazoline and the properties of the cured resin.JOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2008Abstract The curing reaction of a bisphenol A based benzoxazine [2,2-bis(3,4-dihydro-3-phenyl-1,3-benzoxazine) propane (Ba)] and bisoxazoline with a latent curing agent and the properties of the cured resins were investigated. With a latent curing agent, the ring-opening reaction of the benzoxazine ring occurred more rapidly, and then the phenolic hydroxyl group generated by the ring-opening reaction of the benzoxazine ring also reacted with the oxazoline ring more rapidly. The cure time of molten resins from Ba and bisoxazoline with a latent curing agent was reduced, and the cure temperature was lowered, in comparison with those of resins from Ba and bisoxazoline without a latent curing agent. The melt viscosity of molten resins from Ba and bisoxazoline with a latent curing agent was kept around 50 Pa s at 80°C even after 30 min, and molten resins from Ba and bisoxazoline with a latent curing agent showed good thermal stability below 80°C. However, above 170°C, the curing reaction of Ba with bisoxazoline with a latent curing agent proceeded rapidly. Cured resins from Ba and bisoxazoline with a latent curing agent showed good heat resistance, flame resistance, mechanical properties, and electrical insulation in comparison with cured resins from Ba and bisoxazoline without a latent curing agent. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Preparation of polymer-supported polyethylene glycol and phase-transfer catalytic activity in benzoate synthesisAICHE JOURNAL, Issue 3 2010Baojiao Gao Abstract The crosslinked polymeric microspheres (GMA/MMA) of glycyl methacrylate (GMA) and methyl methacrylate (MMA) were prepared by suspension polymerization. Polyethylene glycol (PEG) was grafted on GMA/MMA microsphers via the ring-opening reaction of the epoxy groups on the surfaces of GMA/MMA microspheres, forming a polymer-supported triphase catalyst, PEG-GMA/MMA. The Phase-transfer catalytic activity of PEG-GMA/MMA microspheres was evaluated using the esterification reaction of n -chlorobutane in organic phase and benzoic acid in water phase as a model system. The effects of various factors on the phase transfer catalysis reaction of liquid,solid,liquid were investigated. The experimental results show that the PEG-GMA/MMA microspheres are an effective and stable triphase catalyst for the esterification reaction carried out between oil phase and water phase. The polarity of the organic solvent, the ratio of oil phase volume to water phase volume and the density of the grafted PEG on PEG-GMA/MMA microspheres affect the reaction rate greatly. For this investigated system, the solvent with high polarity is appropriate, an adequate volume ratio of oil phase to water phase is 2:1, and the optimal PEG density on the polymeric microspheres is 15 g/100 g. Triphase catalysts offer many advantages associated with heterogeneous catalysts such as easy separation from the reaction mixture and reusability. The activity of PEG-GMA/MMA microspheres is not nearly decreased after reusing of 10 recycles. © 2009 American Institute of Chemical Engineers AIChE J, 2010 [source] Using glycidyl methacrylate as cross-linking agent to prepare thermosensitive hydrogels by a novel one-step methodJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 6 2008Jianping Deng Abstract A novel one-step approach is reported to prepare thermosensitive hydrogels simply by using hydroxypropyl-,-cyclodextrin (HP-,-CD)/glycidyl methacrylate (GMA)/N -isopropylacrylamide (NIPAM) system. From GMA and HP-,-CD, HP-,-CD/GMA inclusion complex was prepared and identified with NMR, FTIR, and UV-vis spectroscopies. GMA in the form of HP-,-CD/GMA complex was copolymerized with NIPAM in water with K2S2O8 as initiator, yielding hydrogels designated as poly(NIPAM-CD-GMA). The inclusion of CD in the hydrogels was confirmed by FTIR spectroscopy. The contents of CD and GMA placed considerable influence on the swelling ratio and temperature-sensitivity of the produced hydrogels. The hydrogels bearing CD moieties showed higher swelling ratio and temperature-sensitivity when compared with that without CD. The porous structure of the hydrogels containing CD was observed in the SEM images. Relevant mechanism of the ring-opening reaction of epoxide groups in GMA, the subsequent crosslinking reactions and the formation of hydrogels containing CD moieties were proposed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 2193,2201, 2008 [source] Crystallization and preliminary X-ray analysis of l -azetidine-2-carboxylate hydrolase from Pseudomonas sp. strain A2CACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 7 2010Mayuko Toyoda l -Azetidine-2-carboxylate hydrolase from Pseudomonas sp. strain A2C catalyzes a ring-opening reaction that detoxifies l -azetidine-2-carboxylate, an analogue of l -proline. Recombinant l -azetidine-2-carboxylate hydrolase was overexpressed, purified and crystallized using polyethylene glycol and magnesium acetate as precipitants. The needle-shaped crystal belonged to space group P21, with unit-cell parameters a = 35.6, b = 63.6, c = 54.7,Å, , = 105.5°. The crystal diffracted to a resolution of 1.38,Å. The calculated VM value was 2.2,Å3,Da,1, suggesting that the crystal contains one enzyme subunit in the asymmetric unit. [source] Stereocontrolled Intramolecular Aziridination of Glycals: Ready Access to Aminoglycosides and Mechanistic Insights from DFT StudiesCHEMISTRY - A EUROPEAN JOURNAL, Issue 5 2008Rujee Lorpitthaya Abstract Stereocontrolled intramolecular aziridination of the glycal-derived sulfamates offers a highly efficient strategy to divergently prepare aminoglycosides. Rhodium-catalyzed nitrogen-atom transfer to CC bonds formed semistable aziridines, which were subjected to various nucleophiles (C, O, S, and N) to give cyclic sulfamate-containing aminosugar derivatives selectively. The second nucleophilic displacement of sulfonyloxy moieties of [1,2,3]-oxathiazepane-2,2- dioxides allows straightforward access to aminoglycosides with selective ,- or ,-linkages. This approach is operationally simple, complements existing methods, and is a versatile protocol for the synthesis of polyfunctionalized amino sugars. In addition, the mechanism of the rhodium-catalyzed intramolecular aziridination of glycals and its ring-opening reaction was extensively studied by using DFT calculations. [source] Reactivity of (Mono- tert -butyloxiranyl)lithium: A Theoretical Ab Initio StudyEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 26 2008Abdelatif Bouyacoub Abstract The reactivity of the lithiated tert -butyloxiranyl anion has been studied by means of ab initio calculations at the CCSD(T)//MP2 level of theory. Four reaction paths have been studied (three ring-opening reactions and one addition reaction). All extrema were located and characterised. The effects of solvation by one or two MeLi molecules were studied for each reaction path by reoptimising the various extrema. It was found that the addition reaction path becomes competitive when at least two MeLi molecules are taken into account. This shows the catalytic effect of alkyllithium on this reaction path. In no case could a free carbene be characterised as a reaction intermediate. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Anionic ring-opening polymerization of small phosphorus heterocycles and their borane adducts: An ab initio investigationHETEROATOM CHEMISTRY, Issue 2 2007Michelle L. Coote The kinetics and thermodynamics of anionic ring-opening reactions of phosphiranes, phosphetanes, and phospholanes and their borane adducts have been studied by high-level ab initio procedures. For the free heterocycles, model propagation reactions involving nucleophilic attack by Me2P, at the ring ,-carbon were found to be feasible for the three- and four-membered rings, but not for the five-membered ring. For the borane adducts, nucleophilic attack by Me2(BH3)P, was only facile for the three-membered ring, despite an increased thermodynamic tendency toward ring opening for the borane adducts of both the three- and four-membered rings. The formation constants of the borane adducts of methylphosphirane and methylphosphetane were K = 2.6 × 1013 L mol,1 and K = 1.2 × 1020 L mol,1, respectively. A Marcus analysis of the ring-opening reactions of methylphosphirane, methylphosphetane, and their borane adducts showed that the release of ring strain and an "additional factor" contribute to rate enhancement compared with their strain-free analogues. The additional factor was larger for the three-membered rings than for the four-membered rings and was larger in the free heterocycles than in their borane adducts. The additional factor is complex in origin and appears to reflect an increase in the separation between the bonding and antibonding orbitals of the breaking bond on going from the three-membered rings to the four-membered rings, and on going from the free heterocycles to the borane adducts. © 2007 Wiley Periodicals, Inc. Heteroatom Chem 18:118,128, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.20323 [source] Titanium(IV)/Tridentate BINOL Derivative as Catalyst for meso -Aziridine Ring-Opening Reactions: High Enantioselectivity, Strong Positive Non-Linear Effect and Structural CharacterizationADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009Rongmin Yu Abstract A titanium-based chiral Lewis acid was found to be effective for the ring-opening reactions of meso -aziridines with aniline nucleophiles. The products were generally isolated in high yields and with high to excellent enantioselectivity. The catalytic system was studied by X-ray single crystal analysis. In experiments on non-linear effects a strong non-linear effect of the catalyst system was observed. [source] On the Dichotomic Reactivity of Lithiated Styrene Oxide: A Computational and Multinuclear Magnetic Resonance InvestigationCHEMISTRY - A EUROPEAN JOURNAL, Issue 32 2009Vito Capriati Prof. Abstract A multinuclear magnetic resonance investigation, supported by density functional theory calculations, has been synergically used to investigate the configurational stability, reactivity and aggregation states of ,-lithiated styrene oxide in THF at 173,K. NMR studies on ,-lithiated [,,,- 13C2]styrene oxide (also in an enantiomerically enriched form) proved that in THF this oxiranyllithium is mainly present as a solvated monomeric species in equilibrium with a complex mixture of stereoisomeric dimeric aggregates, as well as with bridged and tetrameric aggregates. The fact that some C,Li bonds are partially broken in some stereoisomers reduces their symmetry and complicates the NMR spectra: two diastereoisomers each having a pair of diastereotopic carbon atoms slowly inverting at the lithium atom in absence of tetramethylethylenediamine (TMEDA) have been detected. A (13C,7Li)-HMQC experiment to correlate 7Li and 13C resonances of the various aggregates has been performed for the first time. From natural bond analysis, the monomeric aggregate was proven to have a lower carbenoid character with respect to bridged O-coordinated dimeric aggregates. The employment of suitable experimental conditions in terms of concentration, temperature and the presence or not of TMEDA are crucial to mitigate at the best the "carbene-like" reactivity of lithiated styrene oxide toward intermolecular CLi insertions, eliminative dimerisation reactions and ring-opening reactions. A two-step mechanism for the deprotonation of styrene oxide by sBuLi in THF has been proposed and discussed as well as competitive side reactions. [source] Ceria-Based Solid Catalysts for Organic ChemistryCHEMSUSCHEM CHEMISTRY AND SUSTAINABILITY, ENERGY & MATERIALS, Issue 6 2010Laurence Vivier Dr. Abstract Ceria has been the subject of thorough investigations, mainly because of its use as an active component of catalytic converters for the treatment of exhaust gases. However, ceria-based catalysts have also been developed for different applications in organic chemistry. The redox and acid,base properties of ceria, either alone or in the presence of transition metals, are important parameters that allow to activate complex organic molecules and to selectively orient their transformation. Pure ceria is used in several organic reactions, such as the dehydration of alcohols, the alkylation of aromatic compounds, ketone formation, and aldolization, and in redox reactions. Ceria-supported metal catalysts allow the hydrogenation of many unsaturated compounds. They can also be used for coupling or ring-opening reactions. Cerium atoms can be added as dopants to catalytic system or impregnated onto zeolites and mesoporous catalyst materials to improve their performances. This Review demonstrates that the exceptional surface (and sometimes bulk) properties of ceria make cerium-based catalysts very effective for a broad range of organic reactions. [source] Regioselective Ring-opening Reaction of 1,2-Epoxides with Arylselenol under Solvent-free Conditions and Application to the Synthesis of 1,3-Oxazolidin-2-onesCHINESE JOURNAL OF CHEMISTRY, Issue 5 2006Ming-Hua Yang Abstract Regioselective ring-opening reactions of 1,2-epoxides with ArSeH catalyzed by Ti(OiPr)4 under solvent-free conditions were investigated. A variety of , -hydroxyselenides were obtained in excellent yields of 90%,97% and regioselectivities by a simple, atom economic and environment-friendly procedure. Several N -tosyl-1,3-oxazolidin- 2-ones were prepared starting from the corresponding 1,2-epoxides and ArSeH by a one-pot three-step procedure. [source] | |||||||||||||||||||||||||