- Mannich Bases from Bicyclo[2.2.1]hept-5-en-2-ylmethanol, Secondary Amines and Formaldehyde
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New Mannich bases were synthesized by reacting bicyclo[2.2.1]hept-5-en-2-ylmethanol with secondary amines and formaldehyde. Physicochemical characteristics, composition and structure of the synthesized compounds were determined by elemental analysis, IR,
- Mammadbayli,Hajiyeva,Ibrahimli,Jafarova
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Read Online
- Thermodynamics of Counterion Release Is Critical for Anion Exchange Membrane Conductivity
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As the field of anion exchange membranes (AEMs) employs an increasing variety of cations, a critical understanding of cation properties must be obtained, especially as they relate to membrane ion conductivity. Here, to elucidate such properties, metal cation-based AEMs, featuring bis(norbornene) nickel, ruthenium, or cobalt complexes, were synthesized and characterized. In addition, isothermal titration calorimetry (ITC) was used to probe counterion exchange thermodynamics in order to understand previously reported differences in conductivity. The ion conductivity data reported here further demonstrated that nickel-complex cations had higher conductivity as compared to their ruthenium and cobalt counterparts. Surprisingly, bulk hydration number, ion concentration, ion exchange capacity, and activation energy were not sufficient to explain differences in conductivity, so the thermodynamics of metal cation-counterion association were explored using ITC. Specifically, for the nickel cation as compared to the other two metal-based cations, a larger thermodynamic driving force for chloride counterion release was observed, shown through a smaller ΔHtot for counterion exchange, which indicated weaker cation-counterion association. The use of ITC to study cation-counterion association was further exemplified by characterizing more traditional AEM cations, such as quaternary ammoniums and an imidazolium cation, which demonstrated small variances in their enthalpic response, but an overall ΔHtot similar to that of the nickel-based cation. The cation hydration, rather than its hydration shell or the bulk hydration of the membrane, likely played the key role in determining the strength of the initial cation-counterion pair. This report identifies for the first time how ITC can be used to experimentally determine thermodynamic quantities that are key parameters for understanding and predicting conductivity in AEMs.
- Kwasny, Michael T.,Zhu, Liang,Hickner, Michael A.,Tew, Gregory N.
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Read Online
- Method for preparing single-configuration C-2-position-monosubstituted norbornene derivative
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The invention discloses a method for preparing a single-configuration C-2-position-monosubstituted norbornene derivative. The method comprises the following steps of: firstly, preparing exo-isomer enriched exo-isomer mixed 5-norbornene-2-carboxylic ester by taking commercial exo-isomer/endoisomer mixed 5-norbornene-2-carboxylic acid and large-steric-hindrance monohydric alcohol as raw materials; separating 5-norbornene-2-carboxylate with a single configuration through common column chromatography separation or fractionation; and finally, preparing the C-2-position-monosubstituted norbornene derivative with the single configuration from the separated 5-norbornene-2-carboxylate with the single configuration. The raw materials used in the invention are easy to obtain, the preparation process is simple, and the C-2-position-monosubstituted norbornene derivative with high purity (greater than 98%) and single configuration can be obtained.
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Paragraph 0041-0042
(2021/07/01)
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- Fragment-Based Discovery of Pyrazolopyridones as JAK1 Inhibitors with Excellent Subtype Selectivity
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Herein, we report the discovery of a series of JAK1-selective kinase inhibitors with high potency and excellent JAK family subtype selectivity. A fragment screening hit 1 with a pyrazolopyridone core and a JAK1 bias was selected as the starting point for our fragment-based lead generation efforts. A two-stage strategy was chosen with the dual aims of improving potency and JAK1 selectivity: Optimization of the lipophilic ribose pocket-targeting substituent was followed by the introduction of a variety of P-loop-targeting functional groups. Combining the best moieties from both stages of the optimization afforded compound 40, which showed excellent potency and selectivity. Metabolism studies in vitro and in vivo together with an in vitro safety evaluation suggest that 40 may be a viable lead compound for the development of highly subtype-selective JAK1 inhibitors.
- Hansen, Bettina Borreschmidt,Jepsen, Tue Heesgaard,Larsen, Mogens,Sindet, Rikke,Vifian, Thomas,Burhardt, Mia N?rreskov,Larsen, Jens,Seitzberg, Jimmi Gerner,Carnerup, Martin A.,Jerre, Anders,M?lck, Christina,Lovato, Paola,Rai, Sanjay,Nasipireddy, Venkatarathnam Reddy,Ritzén, Andreas
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p. 7008 - 7032
(2020/07/28)
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- Selective hydrogenation of unsaturated carbonyls by Ni-Fe-based alloy catalysts
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Ni-Fe alloy catalysts prepared by a simple hydrothermal method and subsequent H2 treatment exhibited the greatest activity and selectivity for the hydrogenation of biomass-derived furfural to furfuryl alcohol among the examined second metals, such as Al, Ga, In, Co, and Ti. This work reveals that the alloying of Ni and Fe is a key factor in achieving highly selective hydrogenation of the CO moiety in unsaturated carbonyl substrates. We found that decreasing the temperature of H2 treatment (i.e. decreasing the crystallite size), e.g. Ni-Fe(2)HT-573 K (TOF = 952 h-1), increased the activity compared to that over Ni-Fe(2)HT-673 (TOF = 375 h-1) for furfural hydrogenation. This result suggests that a low-coordinated Ni-Fe alloy was imperative for the catalytic cycle. Moreover, the effect of the metal/support interface was critical; despite the high catalytic performance of Ni-Fe/TiO2, Ni-Fe/Al2O3, and Ni-Fe/CeO2, Ni-Fe supported on SiO2, taeniolite, and hydrotalcite catalysts were ineffective. Vibrational studies using FT-IR measurement confirmed that furfural was physically adsorbed on the surface of the Ni-Fe alloy catalyst via an η1(O) configuration. The synthetic scope of the Ni-Fe catalytic system was very broad; various types of unsaturated carbonyls, such as unsaturated aromatics, unconjugated aliphatics, and a large substituent, were selectively converted into the corresponding unsaturated alcohols.
- Putro, Wahyu S.,Kojima, Takashi,Hara, Takayoshi,Ichikuni, Nobuyuki,Shimazu, Shogo
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p. 3637 - 3646
(2017/08/21)
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- Approach Matters: The Kinetics of Interfacial Inverse-Electron Demand Diels–Alder Reactions
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Rapid and quantitative click functionalization of surfaces remains an interesting challenge in surface chemistry. In this regard, inverse electron demand Diels–Alder (IEDDA) reactions represent a promising metal-free candidate. Herein, we reveal quantitative surface functionalization within 15 min. Furthermore, we report the comprehensive effects of substrate stereochemistry, surrounding microenvironment and substrate order on the reaction kinetics as obtained by surface-bound mass spectrometry (DART-HRMS).
- Sen, Rickdeb,Gahtory, Digvijay,Escorihuela, Jorge,Firet, Judith,Pujari, Sidharam P.,Zuilhof, Han
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supporting information
p. 13015 - 13022
(2017/09/06)
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- Photoreactive polymer and its preparation method
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Provided are a photoreactive polymer that includes a multi-cyclicmulticyclic compound at as its main chain and a method of preparing the same. The photoreactive polymer exhibits excellent thermal stability since it includes a multi-cyclicmulticyclic compound having a high glass transition temperature at as its main chain. In addition, the photoreactive polymer has a relatively large vacancy so that a photoreactive group can move relatively freely in the main chain therein. As a result, a slow photoreaction rate, which is a disadvantage of a conventional polymer material used to form an alignment layer for a liquid crystal display device, can be overcome.
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Paragraph 0093; 0094
(2016/10/09)
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- Structure-Based Design of β5c Selective Inhibitors of Human Constitutive Proteasomes
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This work reports the development of highly potent and selective inhibitors of the β5c catalytic activity of human constitutive proteasomes. The work describes the design principles, large hydrophobic P3 residue and small hydrophobic P1 residue, that led to the synthesis of a panel of peptide epoxyketones; their evaluation and the selection of the most promising compounds for further analyses. Structure-activity relationships detail how in a logical order the β1c/i, β2c/i, and β5i activities became resistant to inhibition as compounds were diversified stepwise. The most effective compounds were obtained as a mixture of cis- and trans-biscyclohexyl isomers, and enantioselective synthesis resolved this issue. Studies on yeast proteasome structures complexed with some of the compounds provide a rationale for the potency and specificity. Substitution of the N-terminus in the most potent compound for a more soluble equivalent led to a cell-permeable molecule that selectively and efficiently blocks β5c in cells expressing both constitutive proteasomes and immunoproteasomes.
- Xin, Bo-Tao,De Bruin, Gerjan,Huber, Eva M.,Besse, Andrej,Florea, Bogdan I.,Filippov, Dmitri V.,Van Der Marel, Gijsbert A.,Kisselev, Alexei F.,Van Der Stelt, Mario,Driessen, Christoph,Groll, Michael,Overkleeft, Herman S.
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supporting information
p. 7177 - 7187
(2016/08/24)
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- High Tg sulfonated insertion polynorbornene ionomers prepared by catalytic insertion polymerization
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A simple method to synthesize high Tg sulfonated ionomers based on catalytic insertion polynorbornene is reported. Copolymers of norbornene and 5-methyl alcohol norbornene (endo:exo = 82:18) or 5-methyl bromide norbornene (endo:exo = 86:14) as well as terpolymers of norbornene, 5-methyl alcohol norbornene and 5-hexyl norbornene are prepared using a cationic Pd catalyst. These copolymers are then thioacetylated. Using hydrogen peroxide as oxidant, a sulfonated polynorbornene is obtained. Ionomers containing as much as 30 mol% SO3H and with Tgs above 200 °C are obtained in a four-step procedure of overall 40-75% yield.
- Pierre, Florian,Commarieu, Basile,Tavares, Ana C.,Claverie, Jerome
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- Exploring the Potential of Norbornene-Modified Mannosamine Derivatives for Metabolic Glycoengineering
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Metabolic glycoengineering (MGE) allows the introduction of unnaturally modified carbohydrates into cellular glycans and their visualization through bioorthogonal ligation. Alkenes, for example, have been used as reporters that can react through inverse-electron-demand Diels–Alder cycloaddition with tetrazines. Earlier, norbornenes were shown to be suitable dienophiles; however, they had not previously been applied for MGE. We synthesized two norbornene-modified mannosamine derivatives that differ in the stereochemistry at the norbornene (exo/endo linkage). Kinetic investigations revealed that the exo derivative reacts more than twice as rapidly as the endo derivative. Through derivatization with 1,2-diamino-4,5-methylenedioxybenzene (DMB) we confirmed that both derivatives are accepted by cells and incorporated after conversion to a sialic acid. In further MGE experiments the incorporated sugars were ligated to a fluorophore and visualized through confocal fluorescence microscopy and flow cytometry.
- Sp?te, Anne-Katrin,Dold, Jeremias E. G. A.,Batroff, Ellen,Schart, Verena F.,Wieland, Daniel E.,Baudendistel, Oliver R.,Wittmann, Valentin
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p. 1374 - 1383
(2017/02/14)
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- Heterogenization of ferrocene palladacycle catalysts on ROMP-derived monolithic supports and application to a Michael addition
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The anchoring of well-defined molecular catalysts on a surface is an attractive strategy to develop sustainable catalytic processes. This article describes the first syntheses of monolith-supported ferrocene palladacycle catalysts. Monolithic supports were prepared via ring-opening metathesis polymerization (ROMP) using the 1st generation Grubbs catalyst . Fluorinated carboxylates were surface-grafted utilizing living Ru-termini. The immobilization of the palladacycles onto the monolithic support was accomplished by ligand substitution on the fluorinated carboxylates of the graft polymer. An investigation of these supported catalysts on the efficiency and reusability under different reaction conditions in a direct Michael addition generating a quaternary C-atom is reported. Whereas stereoselectivity was found to be significantly lower than in a comparable homogeneous system, Pd-leaching was not detected in all analyzed samples indicating a permanently immobilized catalyst system. This journal is
- Sudheendran, Mavila,Eitel, Simon H.,Naumann, Stefan,Buchmeiser, Michael R.,Peters, Ren
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supporting information
p. 5597 - 5607
(2014/12/11)
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- PROCESS FOR THE PREPARATION OF HIGH PURITY NORBORNENE ALKANOLS AND DERIVATIVES THEREOF
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A process for the preparation of a variety of high purity norbornene alkanol monomers and their derivatives is disclosed and claimed. Specifically, a process for the preparation of industrial scale high purity norbornene methanol and its silyl ether derivative is disclosed and claimed. The high purity monomers prepared in accordance with the process of this invention are useful in a variety of applications including but not limited to the preparation of high quality and high purity polynorbornenes having utility in a variety of electronic applications, among various other applications.
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Page/Page column 16; 17
(2014/07/08)
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- Lewis acid mediated asymmetric Diels-Alder reactions of chiral 2-phosphonoacrylates
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2-Phosphonoacrylates containing four chiral alcohol auxiliaries were efficiently prepared and evaluated in Lewis acid mediated Diels-Alder reactions. Under the activation of SnCl4, all reactions performed in CH 2Cl2 at -65 °C exclusively afforded the endo (endo-to-carboxylate) cycloadducts with dr's ranging from 50:50 to >99:1. The best facial selectivity was obtained from the substrate bearing a (-)-phenylmenthyl group, to give adducts as (dr >99:1) or almost as (dr = 99:1) single diastereomers. Detailed strategies for the structural elucidation of the cycloadducts as well as a rationalization of the observed stereoselectivity are described.
- Zhu, Jia-Liang,Chen, Po-Erh,Huang, Hue-Wen
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- Discrete iron complexes for the selective catalytic reduction of aromatic, aliphatic, and α,β-unsaturated aldehydes under water-gas shift conditions
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Iron-catalyzed reductions: Selective iron-catalyzed reduction of aldehydes with hydrogen generated in situ by the water-gas shift reaction is presented (see scheme). The generality and selectivity of this mild procedure are demonstrated by the efficient reduction of various aromatic, aliphatic and α,β-unsaturated aldehydes.
- Tlili, Anis,Schranck, Johannes,Neumann, Helfried,Beller, Matthias
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p. 15935 - 15939
(2013/02/21)
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- LiAlH4-induced reductive dephosphonylation of αα-dialkyl triethyl β-phosphonyl esters: Mechanistic study and synthetic application
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Treatment of αα-dialkyl triethyl β-phosphonyl esters with LiAlHin CHlTHF caused the one-pot dephosphonylation and reduction to yield the corresponding primary alcohols bearing a controllable β secondary carbon center. Mechanistic study has revealed that the LiAlHinduced dephosphonylation should occur first with the assistance of the carboxylate group, and the hydrogen source of the resultant new C-H bond is LiAlH. Georg Thieme Verlag Stuttgart . New York.
- Zhu, Jia-Liang,Bau, Jr-Sheng,Shih, You-Cheng
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experimental part
p. 863 - 866
(2012/05/20)
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- PHOTOREACTIVE POLYMER AND METHOD FOR PREPARING THE SAME
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The present invention relates to a photoreactive polymer that comprises a multi-cyclic compound in a main chain, and a polymerization method thereof. Since the photoreactive polymer according to the present invention comprises a multi-cyclic compound having a high glass transition temperature as a main chain, the thermal stability is excellent, and since the mobility of the main chain is relatively high as compared to that of an additional polymer, a photoreactive group can be freely moved in the main chain of the polymer. Accordingly, it is possible to overcome a slow photoreactive rate that is considered a disadvantage of a polymer material used to prepare an alignment film for known liquid crystal display devices.
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- Photoreactive polymer and process of making the same
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Provided are a photoreactive polymer that includes a multi-cyclicmulticyclic compound at as its main chain and a method of preparing the same. The photoreactive polymer exhibits excellent thermal stability since it includes a multi-cyclicmulticyclic compound having a high glass transition temperature at as its main chain. In addition, the photoreactive polymer has a relatively large vacancy so that a photoreactive group can move relatively freely in the main chain therein. As a result, a slow photoreaction rate, which is a disadvantage of a conventional polymer material used to form an alignment layer for a liquid crystal display device, can be overcome.
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- Synthesis and use of a stable aminal derived from TsDPEN in asymmetric organocatalysis
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A stable aminal formed stereoselectively from (R,R)-N-tosyl-1,2-diphenyl-1, 2-ethylenediamine (TsDPEN) is capable of asymmetric organocatalysis of Diels-Alder and α-amination reactions of aldehydes.
- Gosiewska, Silvia,Soni, Rina,Clarkson, Guy J.,Wills, Martin
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supporting information; experimental part
p. 4214 - 4217
(2010/09/12)
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- Immobilization of macMillan imidazolidinone as mac-SILC and its catalytic performance on sustainable enantioselective dielsAlder cycloaddition
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MacMillan's imidazolidinone catalyst was immobilized as a supported ionic liquid catalyst (Mac-SILC) in the pores of silica gel with the aid of an ionic liquid - 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide. The heterogenized organocatalyst was utilized for the enantioselective Diels-Alder reaction of cyclopentadiene and cinnamaldehyde, recovered by simple filtration and subsequent evacuation, and repeatedly used up to six times in 81% average chemical yield, 87% ee for endo- and 80% ee for exo-products. The Mac-SILC was effective for a variety of substrates.
- Hagiwara, Hisahiro,Kuroda, Toshihiro,Hoshi, Takashi,Suzuki, Toshio
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experimental part
p. 909 - 916
(2010/07/05)
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- Sodium tetraalkoxyborates: Intermediates for the quantitative reduction of aldehydes and ketones to alcohols through ball milling with NaBH4
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Stoichiometric molecular solid-state vibrational ball milling, solvent-free kneading ball milling, and mechanochemical ball milling of varied aldehydes and ketones with unmodified sodium borohydride under temperature control uses all hydrogen atoms of the reducing agent in fast reactions. It provides quantitative yields of thermally stable sodium tetraalkoxyborates. The easily isolated solids are extremely sensitive towards hydrolysis, leading to quantitative yields of the corresponding alcohols. The rapid syntheses are regiospecific and stereoselective. Varied substituents are not attacked, including the bromine of α-bromo ketones. Conjugated aldehydes and ketones provide quantitative yields of the allylic alcohols free of contamination by saturated alcohols that would occur by reaction in solution. Depending on the stoichiometric ratio, benzil is quantitatively reduced to benzoin (4:1 ratio) or dihydrobenzoin (2:1 ratio).
- Naimi-Jamal, M. Reza,Mokhtari, Javad,Dekamin, Mohammad G.,Kaupp, Gerd
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experimental part
p. 3567 - 3572
(2009/10/26)
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- GENERATION OF ENDO- AND/OR EXO-NORBORNENECARBOXALDEHYDE AS AN INTERMEDIATE TO FUNCTIONALIZED NORBORNENES
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Embodiments in accordance with the present invention provide for forming essentially pure diastereomers of 5/6-substituted norbornene-type monomers. Further, embodiments in accordance with the present invention encompass polymerizing such diastereomers to form addition or ROMP polymers where a desired exo-/endo-ratio of the diastereomers is provided to the polymerization, such ratio designed to provide a desired ratio of endo-/exo-structured repeating units for a resulting polymer to have desired physical or chemical properties.
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Page/Page column 10-11
(2009/05/28)
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- Synthesis of bicyclo[2.2.1]hept-5-enyl methyl esters of haloacetic acids
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Synthesis of norbornenyl methyl esters of a number of haloacetic acids via [4+2] cycloaddition of cyclopentadiene to allyl esters of these acids was examined. The yield and isomer composition of the synthesized compounds were examined in relation to the reaction conditions, and the best conditions for their preparation were found.
- Kyazimova,Mamedbeili,Nagiev,Suleimanova,Khalilov
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experimental part
p. 1803 - 1807
(2009/09/08)
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- Asymmetric diels-alder reactions of α,β-unsaturated aldehydes catalyzed by a diarylprolinol silyl ether salt in the presence of water
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(Chemical Equation Presented) Water, water, everywhere: The title reaction predominantly affords the exo isomer with excellent enantioselectivity (see scheme; TMS=trimethylsilyl). The synthesis can be carried out without organic solvents and provides the products by distillation. Water increases the rate and enantioselectivity of the reaction.
- Hayashi, Yujiro,Samanta, Sampak,Gotoh, Hiroaki,Ishikawa, Hayato
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supporting information; experimental part
p. 6634 - 6637
(2009/03/12)
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- Process for producing norbornene derivatives
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The invention relates to a process for producing alkyl norbornene derivatives which are useful for radically curable compounds or as precursors of epoxy compounds. The process comprises: reacting an allyl compound (A) having an allyl group represented by the following formula (1), wherein R 1 represents a hydrogen atom, an alkyl group, a hydroxyl alkyl group, or an alkoxy alkyl group, with alkyl-cyclopentadiene dimer (B).
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Page/Page column 10-11
(2008/06/13)
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- A ring-closing metathesis pathway to fluorovinyl-containing nitrogen heterocyles
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The synthesis of highly functionalized fluorinated piperidines is described. The key step in this synthesis is a ring-closing metathesis reaction involving fluoride-substituted olefins, which leads to the corresponding cyclic vinyl fluorides. Several sequences to arrive at differently substituted piperidines have been evaluated. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- De Matteis, Valeria,Van Delft, Floris L.,Tiebes, Joerg,Rutjes, Floris P. J. T.
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p. 1166 - 1176
(2007/10/03)
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- Norbornene compounds with cross-linkable groups and their derivatives
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The present invention provided a norbornene compound with cross-linkable groups and their derivative polymers, wherein said cross-linkable groups were olefin or epoxy groups. Norbornene polymers with cross-linkable side chain and their block copolymers as well as modified derivatives were prepared via living ring-open metathesis polymerization method. The resulting polymers with excellent solubility and optic properties had narrow molecular weight distribution, well-controlled molecular weight, small refraction ration and high transparency. They were also suitable for preparing hybrid materials with high thermal stability and chemical resistance.
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Page/Page column 9-10
(2010/11/24)
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- Asymmetric Diels-Alder reaction between acrylates and cyclopentadiene in the presence of chiral catalysts
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Asymmetric Diels-Alder reaction between cyclopentadiene and alkyl and cycloalkyl acrylates in the presence of new chiral catalysts, BBr 3?MentOEt, AlCl2OMent, BBr2OMent, and BBr(OMent)2, was studied. Optically active bicyclo[2.2.1]hept-2-ene- 5-carboxylates were synthesized. The influence of the reaction conditions on the total and optical yields and on the stereoselectivity of the adducts synthesized was examined. Nauka/Interperiodica 2006.
- Mamedov
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p. 1621 - 1625
(2008/02/07)
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- Enzymatic resolution of (±)-2-endo-hydroxymethyl and acetoxymethyl substituted hexachloronorbornene derivatives
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(±)-2-endo-Hydroxymethyl-1,4,5,6,7,7-hexachlorobicyclo[2.2.1] hept-5-ene and (±)-2-endo-acetoxymethyl-1,4,5,6,7,7-hexachlorobicyclo[2. 2.1]hept-5-ene were resolved by using various hydrolases to afford enantiomerically enriched products with ees of 94-98%. The absolute configuration was determined by transforming 2-endo-acetoxymethyl-1,4,5,6,7,7- hexachlorobicyclo[2.2.1]hept-5-ene into 2-endo-hydroxymethyl-bicyclo[2.2.1]hept- 5-ene with known absolute configuration.
- Tuerkmen, Yunus Emre,Akhmedov, Idris Mecidoglu,Tanyeli, Cihangir
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p. 2315 - 2318
(2007/10/03)
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- Synthesis and properties of a ROMP backbone polymer with efficient, laterally appended nonlinear optical chromophores
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The synthesis and properties of a new ROMP backbone polymer bearing lateral donor-acceptor-substituted (E)-diethynylethene ((E)-hex-3-ene-1,5-diyne) chromophores are described. The polymer with an average of 40 monomeric repeat units is readily soluble in common organic solvents such as tetrahydrofuran, dichloromethane and chloroform. Good optical-quality films were obtained by spin coating. The third-order susceptibility χ(3) at a wavelength of 1907 nm was determined to be 100 times greater than that of fused silica. After electrical poling, the polymer also showed a significant second-order nonlinear optical coefficient (d33) value, which decays by a factor of two over a period of one month at room temperature.
- Raimundo, Jean-Manuel,Lecomte, Steve,Edelmann, Michael J.,Concilio, Simona,Biaggio, Ivan,Bosshard, Christian,Guenter, Peter,Diederich, Francois
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p. 292 - 295
(2007/10/03)
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- Dual enantioselective Diels-Alder process in the cyclization of chiral acrylamide with dienes
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Diels-Alder cycloadditions of chiral acrylamides with cyclopentadiene or 2, 3-dimethyl butadiene proceed with high diastereofacial selectivity. Either endo-R or endo-S products have been obtained depending upon the structures of acrylamides and Lewis acids used. The endo form was exclusively obtained over the exo form. The dependence of the mechanism of formation of opposite configurations of endo-R or endo-S products on the Lewis acids is discussed. Copyright 2004 John Wiley & Sons, Ltd.
- Jung, Doo Young,Park, Doo Han,Kim, Sung Han,Kim, Yong Hae
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p. 1017 - 1022
(2007/10/03)
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- Deprotection of benzyl and p-methoxybenzyl ethers by chlorosulfonyl isocyanate-sodium hydroxide
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CSI-NaOH procedure provided a new and mild methodology for the deprotection of benzyl and p-methoxybenzyl ethers without affecting the other functional groups under similar reaction conditions.
- Kim, Ji Duck,Han, Gyoonhee,Zee, Ok Pyo,Jung, Young Hoon
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p. 733 - 735
(2007/10/03)
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- Synthesis and transformation of 5- and 2-methyl-bicyclo[2.2.1]hept-2-enes and 2-methylenebicyclo[2.2.1]heptane with retrospective δ-migration of hydrogen over oxide catalyst
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5- and 2-Methylbicyclo[2.2.1]hept-2-enes and 2-methylenebicyclo[2.2.1] heptane were synthesized by a new procedure, and their transformations in a flow system over stationary layer of aluminosilicate catalyst were studied at various temperatures. At 15-400°C these compounds undergo isomerization which is accompanied by δ-migration of hydrogen. The isomerization mechanism is discussed in terms of formation of classical carbocations, not invoking nonclassical carbenium ion.
- Gasanov
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p. 947 - 951
(2007/10/03)
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- Scavenge-ROMP-filter: a facile strategy for soluble scavenging via norbornenyl tagging of electrophilic Reagents.
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[reaction: see text] A new "chemical tagging" method for homogeneous electrophilic scavenging is described. The method utilizes 5-norbornene-2-methanol to scavenge/tag a variety of electrophiles that are present in excess. Once tagging is complete, the crude reaction mixture is subjected to a rapid ROM polymerization event utilizing the second generation Grubbs catalyst. This process yields a polymer that can be precipitated with methanol or ether/hexane, leaving products in excellent yield and purity.
- Moore, Joel D,Harned, Andrew M,Henle, Julia,Flynn, Daniel L,Hanson, Paul R
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p. 1847 - 1849
(2007/10/03)
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- Chemical amplifying type positive resist composition
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A chemical amplifying type positive resist composition, excellent in balance of performance of resolution and sensitivity, having high dry etching resistance and comprising; a resin having a polymerization unit derived from a monomer represented by the following formula (I): wherein R1 and R2 independently represent hydrogen or an alkyl group having 1 to 4 carbons, and R3 represents hydrogen or a methyl group, the resin being insoluble in alkali itself but becoming alkali-soluble due to the action of an acid; and an acid generating agent is provided.
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- Divergent synthesis of two precursors of 3′-homo-2′-deoxy- and 2′-homo-3′-deoxy-carbocyclic nucleosides
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Aminocyclopentanedimethanols 4 and 5, which are of interest for the synthesis of higher homologues of 2′-deoxy- and 3′-deoxycarbonucleosides, respectively, were efficiently prepared by divergent routes starting from (±)-exo-bicyclo[2.2.1]hept-5-ene-2-carbaldehyde. In the key step, ammonolysis of the common intermediate (±)-(1β,3β,4α)-4-benzoyloxymethyl-1,3- cyclopentanedicarboxylic anhydride and subsequent esterification afford near-equimolar amounts of two easily separable isomeric carbamoyl esters.
- Blanco, José M,Fernández, Franco,García-Mera, Xerardo,Rodríguez-Borges, José E
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p. 8843 - 8849
(2007/10/03)
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- Remote substituent effects on the oxymercuration of 2-substituted norbornenes: An experimental and theoretical study
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The effect of a remote substituent on regioselectivity in the oxymercuration of 2-substituted norbornenes has been investigated experimentally and theoretically using density functional theory (DFT). Regioselectivities of 1:1 to 14:1 were observed with various 2-substituted norbornenes. Exo-2-substituted norbornenes always gave greater regioselectivities compared to the corresponding endo-2-substituted norbornenes. The effects of solvents on the regioselectivity have also been examined, and ethereal solvents were found to be the best choice giving the optimal yield and regioselectivity. The relative rate of oxymercuration was estimated by competition experiments. The least reactive substrate (X = OAc) gave the highest regioselectivity. According to DFT predictions, the increased difference between the reaction barriers that results in the greater regioselectivity is correlated directly with the larger polarity of the C=C double bond, which is attacked by the mercury and oxygen. A number of stable exo and endo conformers were predicted. All exo conformers show the same polarity of the double bond, while some endo conformers have a reversal of this polarity. All the conformers except those with the OAc substituent are very close in energy and thus should react. The existence of a mixture of endo conformers with the C=C double bond of opposite polarity clearly explains a decrease in regioselectivity for the endo species. The origin of the greatest regioselectivity for the OAc-2-norbornenes lies in the fact that the conformer with the largest polarity is notably lower in energy than others due to an internal C-H-O hydrogen bond.
- Mayo,Orlova,Goddard,Tam
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p. 5182 - 5191
(2007/10/03)
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- Free radical reactions on soluble supports from ring-opening metathesis
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Equation presented Free radical reactions were performed on soluble ring-opening metathesis (ROM) polymers. These polymers have high substrate loading, short reaction times, and the benefit of a facile purification. All reactions on these supports were obtained in good yields as white crystalline-like materials readily separated from tin byproducts.
- Enholm, Eric J.,Gallagher, Maria E.
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p. 3397 - 3399
(2007/10/03)
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- Highly diastereoselective Diels-Alder reactions of acrylic esters incorporated into a variety of hexopyranosides
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The Diels-Alder reactions of a variety of hexopyranosides carrying an acrylic ester with cyclopentadiene were examined. Some acrylic esters provided the cycloaddition products carrying a norbornene carboxylate with a high level of diastereoselectivity. Plausible mechanisms are presented for the cases of a 4-O-acryloyl-6-deoxy-α-D-glucopyranosidic and 2-O-acryloyl-α-D-glucopyranosidic substrates. By reductive removal of the carbohydrate templates from the adducts, either 2S or 2R-enriched 5-norbornene-2-methanol were obtained.
- Nagatsuka, Takayuki,Yamaguchi, Shuhei,Totani, Kiichiro,Takao, Ken-ichi,Tadano, Kin-ichi
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p. 519 - 535
(2007/10/03)
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- Asymmetrical [4+2]-cycloaddition of (-)-menthyl acrylate and (-)-menthyl methacrylate to cyclopentadiene in the presence of BBr3
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An asymmetrical synthesis of bicyclo[2.2.1]hept-2-enes is described performed by [4+2]-cycloaddition of (-)-menthyl acrylate and (-)-menthyl methacrylate to cyclopentadiene in the presence of BBr3. The effect of different factors on isomer composition, yield, and enantiomeric purity of the compounds obtained was investigated. Kovatch indices were determined and boiling points were estimated with the use of gas-liquid chromatography.
- Mamedov
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p. 217 - 222
(2007/10/03)
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- Bicyclo[2.2.1]heptane-2-methanol Transformations on oxide catalysts
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Bicyclo[2.2.1]heptane-2-methanol was synthesized by hydrogenation of bicyclo[2.2.1]hept-5-ene-2-methanol in a flow system on fixed-bed oxide catalysts, and its transformations were studied. Dehydration and isomerization of bicycloheptene structure with the double-bond migration were found to be the main transformation routes. Thus, 2-methylenebicyclo[2.2.1]heptane (norcamphene), the product of dehydration, was obtained with 47.2 or 61.0% yield in the presence of γ-Al2O3 or aluminosilicate, respectively. The majority of norcamphene was isomerized to give bi- and monocyclic unsaturated hydrocarbons differing in position of the double bond.
- Gasanov,Alieva,Musaev
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p. 272 - 274
(2007/10/03)
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- Fishing for catalysts: Mechanism-based probes for active species in solution
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A combination of derivatization with charged substrates and electrospray-ionization mass spectrometry is used to fish out the active species in a catalytic reaction. The observed species in the mass spectrometer corresponds to the resting state of the catalyst. Data for the ring-opening metathesis polymerization (ROMP) of norbornene by (Cy3P)2Cl2Ru=CHPh (Cy = cyclohexyl) are used to illustrate the method.
- Adlhart, Christian,Chen, Peter
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p. 2192 - 2196
(2007/10/03)
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- Effect of a remote substituent on regioselectivity in oxymercuration of unsymmetrically substituted norbornenes
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The effect of a remote substituent on the regioselectivity in the oxymercuration of unsymmetrical substituted norbornenes has been investigated. Moderate to high levels of regioselectivity were observed with both exo- and endo-substituents at C-2 of norbornenes.
- Mayo, Peter,Poirier, Marc,Rainey, Jan,Tam, William
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p. 7727 - 7730
(2007/10/03)
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- A practical new chiral controller for asymmetric Diels-Alder and alkylation reactions
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(formula presented) The enantiomerically pure hydroxy sulfones (+)- and (-)-2 have been prepared from 1,2-epoxycyclohexane by a simple and practical procedure. The acrylate esters of these alcohols undergo BCl3-catalyzed Diels-Alder reactions with a variety of dienes at -78 to -55°C in CH2Cl2 or C7H8 with high dienophile face selectivity (Table 1). The chiral esters so formed are readily cleaved with recovery of the controllers (+)- or (-)-2. Esters of (+)- and (-)-2 can be converted to Z-polassium enolates and alkylated with high face selectivity.
- Sarakinos, Georgios,Corey
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p. 1741 - 1744
(2008/02/11)
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- Synthetic studies on azadirachtin (Part 3): Asymmetric synthesis of the tricyclic dihydrofuran moiety of azadirachtin
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An asymmetric synthesis of the tricyclic dihydrofuran moiety of azadirachtin is reported. The Diels-Alder adduct, which was catalyzed by Evans' chiral Cu-bisoxazoline complex, was easily converted to the tricyclic portion via SmI2 reductive cleavage and selective functionalization.
- Ishihara,Fukuzaki,Murai
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p. 1907 - 1910
(2007/10/03)
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- Synthesis of New Perfumes, the Esters of 2-Bicyclo[2.2.1]heptylmethanol
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In extension of the assortment of synthetic perfumes we have synthesized the esters of monocarboxylic acids and 2-bicyclo[2.2.1]heptylmethanol by means of [4+2]-cycloaddition of cyclopenta-1,3-diene to allyl esters using tricyclo[5.2.1.02,6]deca-3,8-diene as a starting substance, and 1,4-dioxyanthraquinone as polymerization inhibitor. The subsequent hydrogenation of obtained unsaturated esters of 5-bicyclo[2.2.1]hept-2-enylmethanol with nickel on Cr(III) oxide as a catalyst yielded the target products. The obtained esters of 2-bicyclo[2.2.1]heptylmethanol have a pleasant scent with a flower or fruit tinge, and they may be used as the components of synthetic perfumes and soap odorants.
- Mamedov
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p. 178 - 182
(2007/10/03)
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- Optically Active Axially Chiral Anilide and Maleimide Derivatives as New Chiral Reagents: Synthesis and Application to Asymmetric Diels-Alder Reaction
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New axially chiral N-acryl-N-allyl-o-tert-butylanilide and N-(o-tert-butylphenyl)-2-methylmaleimide with high optical purity and definite absolute configurations were prepared from o-tert-butylaniline and (S)-O-acetyl lactic acid or (R)-2-methylsuccinic acid, respectively. Iodine- or Lewis acid-mediated asymmetric Diels-Alder reaction of these axially chiral compounds with various dienes proceeded with high endo and diastereofacial selectivity.
- Kitagawa, Osamu,Izawa, Hirotaka,Sato, Kiyonobu,Dobashi, Akira,Taguchi, Takeo,Shiro, Motoo
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p. 2634 - 2640
(2007/10/03)
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- Rational design of a new chiral Lewis acid catalyst for enantioselective Diels-Alder reaction: Optically active 2-dichloroboryl-1,1′-binaphthyl
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A novel chiral aryldichloroborane catalyst bearing binaphthyl skeletons with axial chirality was developed as an asymmetric catalyst for the Diels-Alder reaction of dienes and α,β-unsaturated esters, and could be reused as the corresponding boronic acid. In addition, a new convenient method for preparing arylboronic acids from aryl alcohols is described.
- Ishihara, Kazuaki,Inanaga, Kazato,Kondo, Shoichi,Funahashi, Miyuki,Yamamoto, Hisashi
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p. 1053 - 1056
(2007/10/03)
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- Asymmetric Diels-Alder reactions of 2-fluoroacrylic acid derivatives. Part 2: A remarkable effect of fluorine substituent on the diastereoselectivity
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An efficient construction of a chiral monofluorinated tertiary carbon was achieved by a highly exo- and diastereofacial selective Diels-Alder reaction of a 2-fluoroacrylic acid derivative derived from 8-phenylmenthol, and cyclopentadiene. The substituent effect of the fluorine on the selectivities is remarkable as compared with the other substituents at the α-position of the acrylate.
- Ito, Hisanaka,Saito, Akio,Taguchi, Takeo
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p. 1989 - 1994
(2007/10/03)
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- Novel application of chiral micellar media to the Diels-Alder reaction
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A novel chiral surfactant has been used in the first reported aqueous chiral micellar catalysis of a Diels-Alder reaction and enantioselectivities have been observed.
- Diego-Castro, Michael J.,Hailes, Helen C.
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p. 1549 - 1550
(2007/10/03)
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