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Статті в журналах з теми "Facile Michael Addition Reaction"
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Reddy, S. Madhava, and H. M. Walborsky. "A facile intramolecular Michael addition reaction." Journal of Organic Chemistry 51, no. 13 (June 1986): 2605–7. http://dx.doi.org/10.1021/jo00363a042.
Повний текст джерела
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Stepanova, Ekaterina, Andrey Maslivets, Svetlana Kasatkina, and Maksim Dmitriev. "Diversity-Oriented Synthesis via Catalyst-Free Addition of Ketones to [e]-Fused 1H-Pyrrole-2,3-diones." Synthesis 50, no. 24 (August 20, 2018): 4897–904. http://dx.doi.org/10.1055/s-0037-1610647.
Повний текст джерелаАнотація:
A facile synthetic approach towards two distinct pyrrole-based heterocyclic scaffolds has been developed by the interaction of 1H-pyrrole-2,3-diones fused at the [e]-side to a 1,4-benzoxazin-2-one or quinoxalin-2(1H)-one moiety with ketones. The described interaction proceeds either as an aldol reaction or as a Michael addition/intramolecular cyclization depending on the reaction conditions. The disclosed aldol reaction proceeds with good diastereoselectivity under catalyst-free conditions when the reaction is carried out in aromatic hydrocarbons. Products of the cascade Michael addition/intramolecular cyclization reaction are predominantly formed under catalyst-free and solvent-free conditions. The proposed strategy provides facile access to pharmaceutically interesting pyrrole-based polyheterocycles.
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Wang, Yi-Fan, Cheng-Yu He, Longlei Hou, Ping Tian, Guo-Qiang Lin та Xiaofeng Tong. "Facile Access to 1,5-Benzodiazepines via Amine-Promoted (4+3) Annulations of δ-Acetoxy Allenoates with o-Diaminobenzenes under Mild Conditions". Synlett 29, № 09 (23 березня 2018): 1176–80. http://dx.doi.org/10.1055/s-0037-1609347.
Повний текст джерелаАнотація:
An amine-promoted (4+3) annulation of δ-acetoxy allenoate with o-diaminobenzene is reported, providing a facile access to 1,5-benzodiazepine. This method features wide reaction scope, mild conditions, and readily available starting materials. The cascade reaction involves aza-Michael addition of o-diaminobenzene to allenoate, elimination of acetate group, and subsequent 1,6-aza-Michael addition.
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Yang, Jingya, Tianyuan Li, Hongyan Zhou, Nana Li, Dongtai Xie, and Zheng Li. "Potassium Hydroxide Catalysed Intermolecular Aza-Michael Addition of 3-Cyanoindole to Aromatic Enones." Synlett 28, no. 10 (February 28, 2017): 1227–31. http://dx.doi.org/10.1055/s-0036-1588152.
Повний текст джерелаАнотація:
Indole is one of the utmost important heterocycles as it is an essential nucleus of many pharmaceutical compounds. Its aza-Michael reaction, however, is underdeveloped because of the moiety’s inherent characteristics. Here, a potassium hydroxide catalysed intermolecular aza-Michael reaction of 3-cyanoindole with aromatic enones is described. A variety of chalcone derivatives are well tolerated and afford the corresponding N-adducts in moderate to high yields. The use of a cheap catalyst, low catalyst loading, mild reaction temperature, and good substrate tolerance make this procedure a direct and facile method for the preparation of N1-functionalized indoles.
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Terent'ev, Alexander O., Vera A. Vil', Ivan A. Yaremenko, Oleg V. Bityukov, Dmitri O. Levitsky, Vladimir V. Chernyshev, Gennady I. Nikishin та Fabrice Fleury. "Preparation of a microsized cerium chloride-based catalyst and its application in the Michael addition of β-diketones to vinyl ketones". New J. Chem. 38, № 4 (2014): 1493–502. http://dx.doi.org/10.1039/c3nj01454a.
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Boruah, Romesh C., Anil Saikia, Apurba Chetia, and Utpal Bora. "A Facile Synthesis of 1,6-Diketonesvia a Three-Component Michael Addition Reaction." Synlett, no. 10 (2003): 1506–8. http://dx.doi.org/10.1055/s-2003-40821.
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Rulev, Alexander Yu, Alexey R. Romanov, Alexander V. Popov, Evgeniy V. Kondrashov, and Sergey V. Zinchenko. "Reaction of Bromoenones with Amidines: A Simple Catalyst-Free Approach to Trifluoromethylated Pyrimidines." Synthesis 52, no. 10 (March 9, 2020): 1512–22. http://dx.doi.org/10.1055/s-0040-1707969.
Повний текст джерелаАнотація:
A facile one-pot synthesis of trifluoromethylated pyrimidines has been achieved by the treatment of fluorinated 2-bromoenones with aryl- and alkylamidines. The assembly of pyrimidine core proceeds by the cascade reactions via aza-Michael addition–intramolecular cyclization–dehydrohalogenation/dehydration sequence. This strategy is featured by high selectivity and mild reaction conditions giving the target heterocycles in high yields (up to 99%). The unique influence of trifluoromethyl group on the reaction path is demonstrated.
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Lin, Ning, Qiu-Xiang Wei, Li-Hua Jiang, Yan-Qiu Deng, Zhen-Wei Zhang, and Qing Chen. "Asymmetric Michael Addition of Malononitrile with Chalcones via Rosin-Derived Bifunctional Squaramide." Catalysts 10, no. 1 (December 20, 2019): 14. http://dx.doi.org/10.3390/catal10010014.
Повний текст джерелаАнотація:
A rosin-derived bifunctional squaramide catalyzed asymmetric Michael addition of malononitrile with chalcones was discovered. This protocol provides a methodology for the facile synthesis of chiral γ-cyano carbonyl compounds in high yields and enantioselectivities (up to 99% yield and 90% ee) with a lower catalyst loading (0.3 mol%). The predominant R-configured adducts were obtained by this organocatalystic reaction, according to the experimental findings.
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Guy Taylor, Jason, Wellington Martins Ventura, and Luiz Guilherme Souza de Assis. "Facile Synthesis of Indolines by a Tandem Nitro-reduction Aza Michael Addition Reaction." HETEROCYCLES 87, no. 10 (2013): 2023. http://dx.doi.org/10.3987/com-13-12789.
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Fustero, Santos, Javier Moscardó, María Sánchez-Roselló, Elsa Rodríguez, and Pablo Barrio. "Tandem Nucleophilic Addition−Intramolecular Aza-Michael Reaction: Facile Synthesis of Chiral Fluorinated Isoindolines." Organic Letters 12, no. 23 (December 3, 2010): 5494–97. http://dx.doi.org/10.1021/ol102341n.
Повний текст джерелаДисертації з теми "Facile Michael Addition Reaction"
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Budhavaram, Naresh Kumar. "Facile protein and amino acid substitution reactions and their characterization using thermal, mechanical and optical techniques." Diss., Virginia Tech, 2010. http://hdl.handle.net/10919/40340.
Повний текст джерелаАнотація:
The work focused on addressing four main objectives. The first objective was to quantify protein and amino acid substitution reactions. Michael addition reactions were used to modify the amino acids and protein. Amino acids alanine, cysteine, and lysine, and protein ovalbumin (OA) were substituted with different concentrations of ethyl vinyl sulfone (EVS). The substituted products were analyzed using Raman spectroscopy and UV-spectroscopy based ninhydrin assay. In case of alanine, Raman and UV results correlated with each other. With cysteine at lower EVS substitutions amine on the main chain was the preferred site while the substitution shifted to thiols at higher substitutions. This could only be discerned using Raman spectroscopy. Lysine has amines on the main chain and side chain while main chain amine was the most reactive site at lower concentrations of EVS while at higher concentrations side chain amines were also substituted. This information could be discerned using Raman spectroscopy only and not UV spectroscopy. In case of protein as observed by Raman and UV spectroscopy the reaction continued at higher concentrations of EVS indicating the participation of glutamine and asparagines at higher substitutions. However, the reaction considerably slowed down at higher EVS substitutions.
The second objective of the study was to decrease the glass transition temperature (Tg) of OA through internal plasticization and also study the effects of the substituents on the thermal stability of OA. The hypothesis was by covalently attaching substituents to OA, number of hydrogen bonds can be reduced while increasing the free volume and this would reduce Tg. EVS, acrylic acid (AA), butadiene sulfone (BS) and maleimide (MA) were the four groups used. EVS was the most efficient plasticizer of all the four substituents. The Tg decreased with the increasing concentration of EVS until all of the reactive of groups on OA were used up. Tg decreased slightly with AA and BS while no change was observed with MA. However, the substituents showed exact opposite trend in thermal stability as measured using thermogravimetric analysis (TGA). The thermal stability of MA substituted OA was the highest and that of EVS substituted OA was least. FT-IR spectroscopy results indicated that all four substituents caused structural changes in OA. This implied that there were intermolecular interactions between substituted protein chains in case of AA, BS, and MA. This caused an increase in the thermal stability. EVS on the other hand is a linear chain monomer with a hydrophobic end group and hence could not participate in the intermolecular interactions and hence caused a decrease in Tg. As mentioned above the limitation to this technique is the number of available reactive groups on the protein. However, we successfully demonstrated the feasibility of this method in decreasing Tg of protein.
The third objective was to create hydrogels by crosslinking OA with divinyl sulfone (DVS). Protein hydrogels due to their biocompatible nature find applications in drug delivery and tissue engineering. For tissue engineering applications the hydrogels need to be mechanically stable. In this study the protein was substituted with EVS or AA and then crosslinked with DVS. The swelling ratio was measured as a function of pH. All the hydrogels showed the same trend and swelled the least at pH 4.5 which is the isoelectric point of the protein. At basic pH conditions EVS substituted hydrogels swelled the most while AA substituted hydrogels showed least swelling. The static and dynamic moduli of the hydrogels were determined using tensile tester and rheometer respectively. The static modulus values were three times the dynamic modulus. The modulus of the control which is crosslinked OA was least and that of AA substituted OA was highest. The stress relaxation test also showed similar results in which AA substituted OA relaxed the most and the control relaxed the least. FT-IR of the dry hydrogels showed that the amount of hydrogen bonding increased with AA substitution. The hydrophilic AA end groups interacted with each other forming hydrogen bonds. These hydrogen bonds served as additional crosslinks there by increasing the modulus of the hydrogels. EVS on the other hand was incapable of interactions due to the lack of hydrophilic end groups. We were successfully able to create protein hydrogels and control the swelling and mechanical properties by varying the amount of substituted group.
The final objective of the study was to create and characterize microstructures from substituted alanine and lysine. Alanine and lysine were substituted with different concentrations of EVS. Bars and fibers were observed for alanine at moderate substitutions while at higher concentrations random structures were observed using scanning electron microscopy (SEM). Lysine formed tubes at moderate EVS substitutions and rosettes at high concentrations of EVS as evidenced by SEM. FT-IR results suggested that instead of carbonyl one of sulfonyl bonded to the available amine in modified amino acids. And only in this case fibers, tubes and rosettes were observed. X-ray diffraction (XRD) results supported this observation. Using these results we hypothesized that the self assembled structures very much depended on the amount of EVS present in the substituted product and sulfonyl forming β-sheet analogs with amine.Ph. D.
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Jha, Sushil C. "Catalytic, enantioselective michael addition reaction." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2002. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/2496.
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Lombardi, Federico. "Computational study on the asymmetric aminocatalysed Michael addition reaction of cyclohexanone to trans–β–nitrostyrene". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/23186/.
Повний текст джерелаАнотація:
Asymmetric organocatalysed reactions are one of the most fascinating synthetic strategies which one can adopt in order to induct a desired chirality into a reaction product. From all the possible practical applications of small organic molecules in catalytic reaction, amine–based catalysis has attracted a lot of attention during the past two decades. The high interest in asymmetric aminocatalytic pathways is to account to the huge variety of carbonyl compounds that can be functionalized by many different reactions of their corresponding chiral–enamine or –iminium ion as activated nucleophile and electrophile, respectively. Starting from the employment of L–Proline, many useful substrates have been proposed in order to further enhance the catalytic performances of these reaction in terms of enantiomeric excess values, yield, conversion of the substrate and turnover number. In particular, in the last decade the use of chiral and quasi–enantiomeric primary amine species has got a lot of attention in the field. Contemporaneously, many studies have been carried out in order to highlight the mechanism through which these kinds of substrates induct chirality into the desired products. In this scenario, computational chemistry has played a crucial role due to the possibility of simulating and studying any kind of reaction and the transition state structures involved. In the present work the transition state geometries of primary amine–catalysed Michael addition reaction of cyclohexanone to trans–β–nitrostyrene with different organic acid cocatalysts has been studied through different computational techniques such as density functional theory based quantum mechanics calculation and force–field directed molecular simulations.
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Zhu, Sunsheng. "Novel Approach to Polyhedral Oligmeric Silsesquioxane-Based Giant Surfactants Basd on Thiol-Michael Addition "Click" Reaction." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1399555570.
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Li, Mao. "Iron(III) catalyzed asymmetric Diels-Alder reaction - Iron(II) catalyzed thia-Michael addition and aldehyde allylation reactions." Doctoral thesis, Université Laval, 2019. http://hdl.handle.net/20.500.11794/34969.
Повний текст джерелаАнотація:
En raison de leur grande performance, leur prix peu élevé, et leur abondance sur la terre, les catalyseurs de fer ont été choisis pour être testés dans trois différentes transformations de la chimie organique. Le premier projet concerne les réactions asymétriques de Diels-Alder catalysées par Fe⁺¹¹¹ et le ligand bipyridine chiral à des dérivés α, β-insaturés de l’oxazolidin-2-one. Dans un premier temps, nous avons testé différents solvants, diverses quantités en catalyseur, temps de réaction variés et divers sels de fer tels que Fe(ClO₄)₂·6H₂O, Fe(ClO₄)₂·6H₂O, Fe(OTf)₃, Fe(OTf)₂, FeCl₂, FeCl₃, FeBr₃ et FeI₃. Nous avons constaté que 2 mol% de Fe(ClO₄)₃·6H₂O, 2.4 mol% de ligand bipyridine chiral utilisés à –30 °C dans CH₃CN, conduisait à un très bon rendement (99%) et à un bon excès énantiomérique (98%) pour la réaction entre le cyclopentadiène et la 3-alcénoyl-1,3-oxazolidin-2-one. Ensuite, un grand nombre de diénophiles et de diènes moins réactifs ont été testés. Globalement, moins de 10 mol% de catalyseur a été utilisé. L’avantage de ce projet est de pouvoir réaliser la réaction à une température modérée, utiliser de très faibles quantités de catalyseur, obtenir de très bons rendements et d’excellentes énantiosélectivités, et avec une large gamme de substrats. Par la suite, les catalyseurs de fer ont été appliqués aux additions de thia-Michael par deux approches différentes. La première consiste en additions de thia-Michael catalysées par Fe(OTf)₂ dans l’éthanol à température ambiante. Cette méthode permet aux additions de thia-Michael d'être catalysées par un sel de fer vert et beaucoup plus écologique, en quantité catalytique (5 mol% de Fe(OTf)₂), dans un solvant couramment utilisé, EtOH, à température douce, et à atmosphère ambiante. L’avantage de cette réaction a été démontré en l’appliquant à différents accepteurs de Michael et à des thiols aliphatiques et aromatiques. La deuxième méthode consiste en des additions de thia-Michael, catalysées par Fe(OTf)₂ dans le 2-Me-THF, qui est en accord avec les principes de chimie verte en utilisant un sel de vert, Fe(OTf)₂, et un solvant vert 2-Me-THF à température ambiante ou à 50 °C sous air. Le dernier projet est l'allylation asymétrique catalysée par le Fe(OTf)₂ portant un ligand chiral. Avec l'étude d'une variété de ligands chiraux, nous avons sélectionné 5 mol% de Fe(OTf)₂ et 6 mol% de ligand Pybox qui ont catalysé la réaction avec un bon rendement (70%) et 32% d'excès énantiomérique. 20 mol% de TMSCl se sont avérés essentiels pour l'efficacité de la réactionIron catalysts are employed in three different organic transformations owing to their advantages: environmental friendliness, being less expensive and abundant on the Earth. The first project deals with asymmetric Diels-Alder reactions of α, β-unsaturated oxazolidin-2-one derivatives catalyzed by Fe¹¹¹ and a chiral bipyridine ligand. In order to obtain the optimized reaction conditions, we screened different solvents, catalyst loading, various reaction times and a variety of iron salts such as Fe(ClO₄)₂·6H₂O, Fe(ClO₄)₂·6H₂O, Fe(OTf)₃, Fe(OTf)₂, FeCl₂, FeCl₃, FeBr₃ and FeI₃. As a result, the reaction between cyclopentadiene and 3-alkenoyl-1,3-oxazolidin-2-one was carried out at –30 °C in CH₃CN in 1.5 h, with Fe(ClO₄)₃·6H₂O (2 mol%) complexed with the chiral bipyridine ligand (2.4 mol%) as catalyst, providing an excellent yield (99%) and an excellent enantiomeric excess (98%). Decreased enantioselectivities were observed for less-reactive dienes. Overall, less than 10 mol% of catalyst loading was employed. The great advantages of this project are the mild reaction temperature, very low catalyst loading, excellent yields and enantioselectivities and the applicability to a wide scope of substrates. Meanwhile, iron catalysts were used in thia-Michael additions by two different approaches. The first one is about thia-Michael additions catalyzed by Fe(OTf)₂ in EtOH at room temperature. This green method allows the thia-Michael additions to be catalyzed by a green iron salt (5 mol% of Fe(OTf)₂), a green and commonly used solvent EtOH at room temperature under ambient atmosphere. The generality of this reaction was demonstrated by applying it to different Michael acceptors, and to aromatic and aliphatic thiols. The second method is about thia-Michael additions catalyzed by Fe(OTf)₂ in 2-Me-THF, which is in agreement with the green chemistry principles by using a green Fe(OTf)₂ and a green solvent 2-Me-THF at room temperature or 50 °C under air atmosphere. The last project is about asymmetric allylation reactions catalyzed by Fe(OTf)₂ using a chiral ligand. With the study of a variety of chiral ligands, we selected 5 mol% of Fe(OTf)₂ and 6 mol% of Pybox ligand which catalyzed the reaction in good yield (70%) and 32% of ee. The utilization of 20 mol% of TMSCl is essential for the effectiveness of the reaction
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LOPS, CARMINE. "Development of organocatalytic and stereoselective reactions." Doctoral thesis, Università degli Studi di Trieste, 2018. http://hdl.handle.net/11368/2918472.
Повний текст джерелаАнотація:
Il focus di questo dottorato è stato lo sviluppo di due reazioni organocatalitiche e stereoselettive: le addizioni di sulfa-Michael e le condensazioni di Darzens poiché rappresentano degli approcci sintetici interessanti per la sintesi di farmaci chirali e, nell’ambito farmaceutico, ci sono pochi principi attivi (API) sintetizzati con reazioni di SMAs e/o di Darzens organocatalitiche e stereoselettive. Nell’ambito delle addizioni di sulfa-Michael (SMAs), la catalisi mediata da molecole bifunzionali donatrici di legami ad idrogeno (HBD) rappresenta un approccio interessante per l'attivazione sia della componente nucleofila che di quella elettrofila di una reazione. Gli esempi di SMA stereoselettive catalizzate da HBD bifunzionali e aventi il trans-chalcone come accettore di Michael sono pochi. Con l’obiettivo di ottimizzare l’attivitá dei catalizzatori HBD, la letteratura suggerisce come l'aumento dell'acidità dei protoni tioureici NH abbia effetti positivi sulle velocità di alcune reazioni. Spinto da queste informazioni, si è deciso di eseguire un'analisi comparativa di alcuni catalizzatori HBD in SMA stereoselettive aventi il trans-calcone come accettore di Michael. All’inizio, abbiamo studiato l'effetto della quantitá di catalizzatore, del solvente e della temperatura nella reazione modello: l'addizione del fenilmetantiolo al trans-calcone. Successivamente, con le condizioni di reazione ottimizzate, abbiamo valutato la capacità di indurre stereoselezione da parte di alcuni catalizzatori HBDs nelle SMAs stereoselettive del benzentiolo, fenilmetantiolo e 2-feniletantiolo al trans-calcone. L'aumento dell'acidità di Brønsted nella porzione donatrice di legami ad idrogeno ha dato, in alcuni casi, reazioni più rapide ma, in generale, ha avuto un impatto negativo sulla stereoselettività. Inoltre, il prodotto ottenuto dall’addizione del benzentiolo al trans-calcone è risultato stereochimicamente instabile, poiché subisce una reazione di retro-Michael quando lasciato in presenza di catalizzatori, come nel caso di un ritardato work-up della reazione. Per quanto riguarda le condensazioni di Darzens, generalmente, sono condotte in presenza di basi forti come idrossidi o alcossidi di metalli alcalini, sodio ammide, LDA, LiHMDS o n-butil-litio. In letteratura, non ci sono esempi di reazioni di Darzens condotte in presenza di basi organiche neutre. Quindi, si è deciso di studiare la reazione di Darzens in presenza di basi organiche neutre aventi una diversa pKBH+. La reazione, in presenza di una quantità stechiometrica di fosfazene P1-t-Bu, genera gli epossidi cis e trans con una buona resa e con un breve tempo di reazione. Tuttavia, sia i problemi di stabilità che le difficoltà di preparazione delle basi fosfazeniche, rendono importante l’obiettivo di identificare nuove superbasi. A tal fine, è stata valutata la ciclopropenimmina, con una pKBH+ simile a quella di P1-t-Bu. Con l’impiego di una quantità stechiometrica di ciclopropenimmina, l'epossido è stato ottenuto con una resa fino al 34% e 1/0.85 d.r. cis/trans. Usando una quantità catalitica di ciclopropenimmina (30 mol%), i composti α,β-epossicarbonilici sono stati ottenuti con una resa fino all'86% e 1/0.6 d.r. cis/trans; dimostrando di essere tollerante sia alle variazioni strutturali che alle proprietà elettroniche delle aldeidi aromatiche e dei composti carbonilici impiegati.
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Ibrahim, Houssein. "Synthèse de nouveaux composés chiraux à partir d'isosorbide et d'isomannide : applications en catalyse asymétrique." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112159.
Повний текст джерелаАнотація:
Ce travail de thèse porte sur la synthèse de nouveaux composés chiraux à partir de l’isosorbide et de l’isomannide en vue de leurs applications en catalyse asymétrique. Dans une première partie, de nouvelles monophosphines ont été synthétisées et appliquées en tant que ligands dans la réaction d'hydrogénation asymétrique d’oléfines. Des excès énantiomériques jusqu’à 96% ont été observés. Elles ont également été employées en tant que catalyseurs organiques dans les réactions de cyclisation [3 +2]. De bonnes activités catalytiques et des excès énantiomériques modestes sont obtenus. Dans une deuxième partie, une série de composés azotés chiraux a été synthétisée en 3 à 4 étapes avec de bons rendements globaux. Ils ont été testés en tant que ligands dans la réaction de réduction de cétones aromatiques par transfert d’hydrogène. Des excès énantiomériques jusqu’à 73% ont été obtenus. La réaction d’addition de phénylacétylène sur d’imines a également été étudiée. Les complexes formés se sont montrés actifs mais pas très énantiosélectifs. Ces composés azotés ont également été utilisés en tant que catalyseurs organiques dans la réaction d’addition de Michael de cétones aromatiques sur le nitrostyrène. Toutefois, ils n’ont permis de conduire qu’à de faibles énantiosélectivités. Dans une dernière partie, des composés de type thiourée ont été synthétisés en 5 étapes. Ces thiourées ont été appliquées en catalyse organique dans la réaction d’alkylation de type Friedel-Crafts entre différents substrats indoliques et nitrooléfines, et dans la réaction d’addition conjuguée des hydroxylamines sur des pyrazoles pour la synthèse de dérivés β-aminoacides. Ces catalyseurs se sont révélés actifs mais peu énantiosélectifsThe Thesis deals with the synthesis of new chiral compounds derived from isosorbide and isomannide and their applications to asymmetric catalysis. The first part of this work consisted in perfecting the chemical and enantioselective hydrogenation conditions of olefins using chiral monophosphines as ligands (up to 96% ee). These phosphines were also used as organocatalysts for [3+2] cyclisation reactions showing good catalytic activity and moderate enantioselectivity. The second part turned to the synthesis of a series of chiral nitrogen compounds which were evaluated in the asymmetric transfer hydrogenation of aromatic ketones giving good enantioselectivity (up to 73% ee). The complexes formed with amine ligands were also applied to the addition reaction of phenylacetylene to imines. Good catalytic activity but low enantioselectivity were observed. These nitrogen compounds were also used as organocatalysts in the Michael addition reaction of aromatic ketones to the nitrostyrene. Again, low enantiomeric excess was obtained. The last part of this work consisted in preparing new chiral thiourea compounds which were applied as organocatalysts to the Friedel-Crafts alkylation reaction of different indoles with nitroolefines, and to the conjugate addition reaction of hydroxylamines to pyrazoles derivatives for the synthesis of β-amino acids. In two cases, these catalysts have proved active but not enantioselective
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Guedeney, Nicolas. "Vers la vectorisation des bisphophonates par les peptides de pénétration cellulaire." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCD024.
Повний текст джерелаАнотація:
De nos jours, une des stratégies majeures dans la modulation de la pharmacocinétique des composés bioactifs est leur vectorisation et l’obtention de formes prodrogues. Ce travail est centré sur la vectorisation d’antitumoraux phosphorés à l’aide de peptides favorisant le passage membranaire. Nous avons alors réalisé la conjugaison d’aminoalkyl-bisphosphonates avec des séquences peptidiques afin de modifier leur temps de rétention dans l’organisme et d’augmenter leur internalisation cellulaire. Différents espaceurs possédant un motif carbonylé insaturé ont été évalués dans le couplage par la réaction d’addition aza- et thiaMichael afin d’aboutir à l’obtention d’un conjugué peptide-alendronate. Une approche prodrogue a également été réalisée avec la synthèse de dérivés de type bisphosphinates et l’obtention d’un analogue de l’alendronateNowadays, one of the main strategies for pharmacokinetic modifications of bioactive compounds is their vectorization and the synthesis of prodrug derivatives. This work is focused on the vectorization of phosphorus antitumor agents with cell-penetrating peptides. We have then conjugated aminoalkyl-bisphosphonates with peptidic sequence to modify their retention time and increase their cellular internalization. Several linkers bearing an insaturated carbonyl moiety have been evaluated in conjugation by aza- and thia-Michael addition reaction to obtain a conjugated peptide-alendronate compounds. A prodrug approach has been conducted with the synthesis of bisphosphinate derivatives and an analog of alendronate has been obtained
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Léger, Frédéric. "Additions d'énamines β-lithiées sur des esters α, β-éthyléniques. Nouvelles propriétés des énamines β-halogénées". Rouen, 1996. http://www.theses.fr/1996ROUES051.
Повний текст джерелаАнотація:
Les énamines β-lithiées sont obtenues par bromation des énamines puis échange halogène-métal et réagissent directement avec les esters α, β-éthyléniques exclusivement en 1,4 conduisant après hydrolyse aux énaminoesters correspondants. Ces composés sont obtenus avec de bons rendements et présentent une rétention de configuration par rapport aux énamines β-bromées de départ. L'énolate intermédiairement formé a été condensé sur l'iodure de méthyle conduisant à la création d'un carbone stéréogénique supplémentaire. Dans ce cas les nouveaux énaminoesters sont obtenus avec une excellente diastéréosélectivité. L'hydrolyse des énaminoesters conduit, selon les conditions utilisées, aux cétoesters ou aux cétoacides correspondants avec en général une très bonne diastéréosélectivité. En utilisant des énamines β-lithiées achirales sur des esters α, β-éthyléniques d'alcool chiral, les excès diastéréoisomériques ont été moyens. Par contre la réaction de Michael entre une énamine β-lithiée chirale et le crotonate de tertiobutyle conduit a une complète diastéréoselectivité au niveau de l'énaminoester. Dans les conditions de réaction de Heck (Pd(OAc)2, PPh3, NEt#3, CH3CN), les énamines beta-halogénées ont été réduites en amines tertiaires avec des rendements corrects. L'utilisation d'énamines β-halogénées à reste aminé chiral conduit aux amines tertiaires chirales correspondantes. L'agent de réduction est vraisemblablement la triéthylamine. La deracémisation d'aldéhydes α-substitués par l'intermédiaire d'énamines β-substituées chirales conduit à des aldéhydes α-substitués optiquement actifs. Les différents paramètres de la réaction ont été étudiés et ont permis d'atteindre des excès énantiomériques de 60%.
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Goudedranche, Sébastien. "Réactions domino organocatalysées énantiosélectives à partir de cétoamides." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4354.
Повний текст джерелаАнотація:
Au cours de ces travaux nous nous sommes intéressés au développement de nouvelles transformations énantiosélectives combinant les outils modernes de la synthèse organique que sont les « Multiples Bond-Forming Transformations » et l'organocatalyse afin de synthétiser des molécules d'intérêt structural et biologique. Dans ce contexte, nous avons d'abord mis au point deux nouvelles réactions domino initiées par une addition de Michael. La première, une cascade addition de Michael-acylation, permet la synthèse de spiroglutarimides optiquement actifs à partir de β-cétoamides et de nouveaux bis-électrophiles, les cyanures d'acyle α,β-insaturés. La deuxième, une réaction domino addition de Michaelhémiacétalisation- hémiaminalisation, permet la synthèse de d'hétérocycles azotés à sept chaînons à partir d'α-cétoamides comme nouveaux bis-nucléophilesThis work focused on the development of novel enantioselective transformations combining Multiples Bond-Forming Transformations and organocatalysis which are modern tools of organic synthesis in order to synthetize molecules of structural and biological interests. In this context, we developed two new Michael addition initiated domino reactions. The first one, a domino Michael addition-acylation, allows the synthesis of optically active spiroglutarimides starting from β-ketoamides and α,β-unsaturated acyles cyanides as new biselectrophiles.The second one, a domino Michael addition-hemiaminalizationhemiacetalization, allows the synthesis of seven-membered aza-cycles using α-ketoamides as new bis-nucleophiles
Частини книг з теми "Facile Michael Addition Reaction"
1
Oare, David A., and Clayton H. Heathcock. "Stereochemistry of the Base-Promoted Michael Addition Reaction." In Topics in Stereochemistry, 227–407. Hoboken, NJ, USA: John Wiley & Sons, Inc., 2007. http://dx.doi.org/10.1002/9780470147283.ch5.
Повний текст джерела
2
Guan, Xiaoyuan, Guangxue Chen, Rui Guo, Zhaohui Yu, and Minghui He. "Thiol-ene Michael Addition Reaction Under Phototriggered Base Proliferation." In Lecture Notes in Electrical Engineering, 909–18. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-10-7629-9_113.
Повний текст джерела
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Tomioka, Kiyoshi. "Five Step Asymmetric Total Synthesis of β-Lycorane Employing Chiral Diether Ligand-Controlled Conjugate Addition-Michael Reaction Cascade." In New Horizons of Process Chemistry, 191–200. Singapore: Springer Singapore, 2017. http://dx.doi.org/10.1007/978-981-10-3421-3_14.
Повний текст джерела
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Taber, Douglass F. "The Magnus Synthesis of ( ± )-Codeine." In Organic Synthesis. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199965724.003.0088.
Повний текст джерелаАнотація:
Although there have been many synthetic approaches to morphine and its methyl ether codeine 3, the pentacyclic structure of these Papaver alkaloids continues to intrigue organic chemists. Philip Magnus of the University of Texas devised (J. Am. Chem. Soc . 2009, 131, 16045) an elegant route to 3 based on the conversion of 1 to 2 by way of an intramolecular Michael addition. The starting point for the synthesis was the commercial bromoaldehyde 4. Coupling with 5 delivered the substituted biphenyl 6, which was carried on to the mixed bromo acetal 8. On exposure to fluoride ion, 8 was desilylated, and the intermediate phenoxide cyclized with impressive facility to give 1. Exposure of 1 to nitromethane delivered the tetracyclic 2. This reaction apparently was initiated by Henry addition of the nitromethane to the aldehyde. The intramolecular Michael addition of the intermediate Henry adduct then proceeded to give the desired cis diastereomer of the newly formed ring. Finally, loss of water gave 2. Conjugate reduction of the nitroalkene 2 led to 9 with remarkable diastereocontrol. Exposure of 9 to LiAlH4 converted the nitro group to the amine and the enone to the allylic alcohol. On exposure to acid, the hemiacetal was hydrolyzed. The liberated aldehyde underwent reductive amination with the free amine, while at the same time ionic cyclization closed the ether ring. N-acylation completed the conversion to 10. The ether 10 had previously been converted to codeine and then, in a single demethylation step, to morphine. In that synthesis, the alkene of 10 was directly epoxidized. The resulting “up” epoxide reacted only sluggishly with phenylselenide anion, and the relative configuration of the resulting allylic alcohol had to be inverted by oxidation followed by reduction. In the current synthesis, exposure of the alkene 10 to dibromohydantoin under aqueous conditions to form the bromohydrin effected concomitant arene bromination, to give, after base treatment, the “down” epoxide 12. Phenylselenide opening of the epoxide was then facile, and the product allylic alcohol had the correct relative configuration for codeine and morphine. The extra Br was of no consequence, as it was removed by the final LiAlH4 reduction.
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Lambert, Tristan H. "C–O Ring Formation." In Organic Synthesis. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190646165.003.0044.
Повний текст джерелаАнотація:
The enantioselective bromocyclization of dicarbonyl 1 to form dihydrofuran 3 using thiocarbamate catalyst 2 was developed (Angew. Chem. Int. Ed. 2013, 52, 8597) by Ying-Yeung Yeung at the National University of Singapore. Access to dihydrofuran 5 from the cyclic boronic acid 4 and salicylaldehyde via a morpholine-mediated Petasis borono-Mannich reaction was reported (Org. Lett. 2013, 15, 5944) by Xian-Jin Yang at East China University of Science and Technology and Jun Yang at the Shanghai Institute of Organic Chemistry. Chiral phosphoric acid 7 was shown (Angew. Chem. Int. Ed. 2013, 52, 13593) by Jianwei Sun at the Hong Kong University of Science and Technology to catalyze the enantioselective acetalization of diol 6 to form tetrahydrofuran 8 with high stereoselectivity. Jan Deska at the University of Cologne reported (Org. Lett. 2013, 15, 5998) the conversion of glutarate ether 9 to enantiopure tetrahydrofuranone 10 by way of an enzymatic desymmetrization/oxonium ylide rearrangement sequence. Perali Ramu Sridhar at the University of Hyderabad demonstrated (Org. Lett. 2013, 15, 4474) the ring-contraction of spirocyclopropane tetrahydropyran 11 to produce tetrahydrofuran 12. Michael A. Kerr at the University of Western Ontario reported (Org. Lett. 2013, 15, 4838) that cyclopropane hemimalonate 13 underwent conversion to vinylbutanolide 14 in the presence of LiCl and Me₃N•HCl under microwave irradiation. Eric M. Ferreira at Colorado State University developed (J. Am. Chem. Soc. 2013, 135, 17266) the platinum-catalyzed bisheterocyclization of alkyne diol 15 to furnish the bisheterocycle 16. Chiral sulfur ylides such as 17, which can be synthesized easily and cheaply, were shown (J. Am. Chem. Soc. 2013, 135, 11951) by Eoghan M. McGarrigle at the University of Bristol and University College Dublin and Varinder K. Aggarwal at the University of Bristol to stereoselectively epoxidize a variety of aldehydes, as exemplified by 18. The amine 20-catalyzed tandem heteroconjugate addition/Michael reaction of quinol 19 and cinnamaldehyde to produce bicycle 21 with very high ee was reported (Chem. Sci. 2013, 4, 2828) by Jeffrey S. Johnson at the University of North Carolina, Chapel Hill. Quinol ether 22 underwent facile photorearrangement–cycloaddition to 23 under irradiation, as reported (J. Am. Chem. Soc. 2013, 135, 17978) by John A. Porco, Jr. at Boston University and Corey R. J. Stephenson, now at the University of Michigan.
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Taber, Douglass F. "The Deslongchamps Synthesis of (+)-Cassaine." In Organic Synthesis. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190646165.003.0091.
Повний текст джерелаАнотація:
Although the Na+-K+-ATPase inhibitor (+)-cassaine 4 was isolated from the bark of Erythrophleum guineense in 1935, the structure was not established until 1959. Intriguing features of 4 include the unsaturated amide and the axial secondary methyl group, both pendant to the C ring. Pierre Deslongchamps, now at Université Laval, envisioned (Org. Lett. 2013, 15, 6270) that the relative stereochemistry of the secondary methyl could be established kinetically by intramolecular Michael addition of the enolate formed by the addition of the anion of 2 to the enone 1 to give 3. The sulfoxide 2 was readily prepared by the addition (Tetrahedron Lett. 1990, 31, 3969) of the anion derived from methyl phenyl sulfoxide to methyl crotonate. The enone 1 was prepared from commercial dihydrocarvone 5. Robinson annulation with ethyl vinyl ketone 6 (Tetrahedron 2000, 56, 3409) led to 7, that was reductively methylated, reduced further, and protected to give 8. Oxidative cleavage of the pendant isopropenyl group followed by Baeyer–Villiger oxidation, hydrolysis, and further oxidation gave the ketone 9, that was methoxycarbonylated, then oxidized further to 1. The addition of the anion derived from 2 to 1 presumably gave initially the axial adduct. Subsequent intramolecular Michael addition then proceeded selectively to one face of the residual enone to give, after elimination of the sulfoxide, the enone 3. The anionic cascade annulation that formed the C ring having been accomplished, the ester of 3 was removed by exposure to ethoxide to give 10, having the alkene conjugated with the B-ring ketone. Selective reduction followed by protection gave 11. In the course of the hydrogenolytic deprotection of the A-ring alcohol, selective hydrogenation of the tetrasubstituted alkene was also observed. Increasing the H2 pressure and extending the reaction time gave complete conversion to the desired 12, the relative configuration of which was established by X-ray crystallography. A series of protection, reduction, and oxidation steps led to the C-ring ketone, that was methoxycarbonylated to give 14. Reduction followed by dehydration gave the unsaturated ester, that was reduced to the saturated ester with Mg in methanol. Reduction followed by oxidation then delivered the aldehyde 15. After some investigation, it was found that the aldehyde could be converted to the desired enol triflate by exposure to KHMDS and the Comins reagent.
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Taber, Douglass F. "Enantioselective Synthesis of Alcohols and Amines: The Doi Synthesis of Apratoxin C." In Organic Synthesis. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190646165.003.0034.
Повний текст джерелаАнотація:
Hiromitsu Takayama of Chiba University used (Org. Lett. 2014, 16, 5000) the Itsuno-Corey protocol to reduce the enone 1 to the allylic alcohol 2. Peiming Gu of Ningxia University developed (Org. Lett. 2014, 16, 5339) a Cu catalyst that cyclized the prochiral 3 to 4 in high ee. Xiaoming Feng of Sichuan University effected (Org. Lett. 2014, 16, 3938) enantioselective Baeyer–Villiger oxidation of the racemic cyclopentanone 5, converting one enantiomer to the δ-lactone 6. The velocity of catalytic osmylation is often limited by slow turnover of the intermediate osmate ester. Koichi Narasaka, then at the University of Tokyo, showed (Chem. Lett. 1988, 1721) that the efficiency of the transformation was improved by the addition of stoichiometric phenyl boronic acid. Kilian Muñiz, now at ICIQ Tarragona, established (Chem. Eur. J. 2005, 11, 3951) that this acceleration also worked with Sharpless asymmetric dihydroxylation. D. Christopher Braddock of Imperial College London took advantage (Chem. Commun. 2014, 50, 13725) of these observations, converting myrcene 7 selectively to the cyclic boronate 8. Michael P. Doyle of the University of Maryland developed (J. Org. Chem. 2014, 79, 12185) a Rh catalyst for the ene reaction of 9 with 10 to give 11. Adriaan J. Minnaard of the University of Groningen devised (Chem. Eur. J. 2014, 20, 14250) a Cu catalyst that mediated the face selective addition of 13 to 12, establishing the oxygenated quaternary center of 14. Tomonori Misaki and Takashi Sugimura of the University of Hyogo used (Chem. Lett. 2014, 43, 1826) Michael addition of 15 to 16 to construct the oxygenated quaternary center of 17. Jon C. Antilla of the University of South Florida assembled (Chem. Commun. 2014, 50, 14187) the δ-lactone 20 by adding the diene 19 to the α-keto ester 18. Zhiyong Wang of the University of Science and Technology of China reported (Org. Lett. 2014, 16, 3564) related results. Jonathan A. Ellman of Yale University achieved (Angew. Chem. Int. Ed. 2014, 53, 11329) substantial enantioselectivity in the addition of thioacetic acid 22 to the nitroalkene 21 to give 23. Subhash P. Chavan of the National Chemistry Laboratory prepared (Tetrahedron Lett. 2014, 55, 5905) the allylic amine 25 by reduction of the aziridine 24.
8
Marsden, S. P. "Tandem Michael Addition/Intramolecular Aldol Reaction (Robinson Annulation)." In Ketones, 1. Georg Thieme Verlag KG, 2005. http://dx.doi.org/10.1055/sos-sd-026-01026.
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Tidwell, T. T. "Michael Addition and Elimination Reaction of Alkanoate Esters." In Three Carbon-Heteroatom Bonds: Thio-, Seleno-, and Tellurocarboxylic Acids and Derivatives; Imidic Acids and Derivatives; Ortho Acid Derivatives, 1. Georg Thieme Verlag KG, 2006. http://dx.doi.org/10.1055/sos-sd-023-00542.
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Frey, Perry A., and Adrian D. Hegeman. "Addition and Elimination." In Enzymatic Reaction Mechanisms. Oxford University Press, 2007. http://dx.doi.org/10.1093/oso/9780195122589.003.0013.
Повний текст джерелаАнотація:
Most elimination and addition reactions in biochemistry proceed by α,β-elimination/addition mechanisms. In the case of elimination, the leaving group is β to an activating functional group in the substrate. The activating group may be the carbonyl group of a ketone or aldehyde, the iminium group derived from an aldehyde or ketone, or the acyl-carbonyl of a carboxylic acid or ester, and the proton is α to the activating group. Addition reactions in this class are the same reactions in reverse, and they follow the course of the Michael addition in organic chemistry. The generic process is illustrated in scheme 9-1. Substituents among the activating and leaving groups are diverse and are presumed to account for the significant variations among enzymes in the class. A few enzymes in this class catalyze elimination/addition without the assistance of a coenzyme or cofactor. They presumably incorporate sufficiently acidic (A—H) or basic (:B) amino acid side chains to catalyze the proton transfer processes, or they may stabilize carbanionic intermediates by low-barrier hydrogen bonding. Others employ divalent metal ions, pyridoxal-5'-phosphate (PLP), [4Fe–4S] centers, or NAD+ to facilitate the reactions. Cofactors and coenzymes increase the acidity of Cα—H or improve the propensity of the leaving group Y to depart. In most cases, the major barrier consists of increasing the acidity of the Cα—H group, which decreases the pKa. In a few cases, as when the leaving group is a carboxylic acid or a phosphate, no catalysis is required for it to depart. Limited space prevents discussion of the many enzymes that catalyze cofactor-independent α, β-eliminations. We address the actions of fumarase and crotonase because of the historic emphasis on the biochemical significance of these enzymes. Many other dehydratases and ammonia lyases also belong in this group. In the tricarboxylic acid cycle, fumarate arises from the action of succinate dehydrogenase, and fumarase (EC 4.2.1.2) catalyzes the addition of water to form S-malate. The reaction can be monitored in either direction, and in various studies, the kinetic parameters may be quoted as such (e.g., fumarate formation, or malate formation). The body of knowledge about the action of fumarase is surprisingly incomplete, given the importance of the enzyme in metabolism.
Тези доповідей конференцій з теми "Facile Michael Addition Reaction"
1
Scott, T. W. "Picosecond Addition and β-Scission Reactions of Thiyl Radicals with Unsaturated Hydrocarbons". У International Conference on Ultrafast Phenomena. Washington, D.C.: Optica Publishing Group, 1986. http://dx.doi.org/10.1364/up.1986.mf7.
Повний текст джерелаАнотація:
It is well known that free radical reactions exhibit extreme product diversity through the action of a limited number of elementary steps. The most facile elementary reaction between sulfur centered thiyl radicals and hydrocarbon liquids is free radical addition to carbon-carbon double bonds (1). This is a rapid exothermic reaction which is generally reversible.
2
Forghani, A., L. Garber, C. Chen, R. Devireddy, J. Pojman, and D. Hayes. "In Situ Polymerization of PEGDA Foam for Bone Defects." In ASME 2015 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/imece2015-51235.
Повний текст джерелаАнотація:
The purpose of this study is to develop a novel bone replacement using in situ polymerization of thiol-acrylate with adipose tissue derived adult stem cells (ASCs). Specifically, Poly(ethylene glycol) diacrylate-co-trimethylolpropane tris (3-mercaptopropionate) (PEGDA-co-TMPTMP) was synthesized with 10% Hydroxyapatite (HA) foam by an amine-catalyzed Michael addition reaction. Initial characterization studies were performed to determine the temperature profile during the exothermic reaction showing a peak temperature of 50°C. To prevent hyperthermic cell damage and death during the exothermic polymerization procedure, the hASCs were encapsulated in alginate. Characterization of the 3-D structure and interconnectivity of pores in the polymeric foam scaffolds were performed using FIB-SEM and Micro-CT showing uniform distribution of HA. Cell viability experiments within the polymeric scaffold were performed using Vybrant® MTT cell profileration method, as well as fluorescent dyes: Calcein-AM (live) and Ethidium homodimer-1 (dead) showing viability of cells inside the samples.
3
Zhong, Hanyi, Ying Guan, Zhengsong Qiu, Jie Feng, Wenlei Liu, Yuan Wan, and Yubin Zhang. "Improvement of Rheological and Filtration Properties of Water-Based Drilling Fluids Using Bentonite-Hydrothermal Carbon Nanocomposites Under the Ultra-High Temperature and High Pressure Conditions." In SPE/IATMI Asia Pacific Oil & Gas Conference and Exhibition. SPE, 2021. http://dx.doi.org/10.2118/205539-ms.
Повний текст джерелаАнотація:
Abstract With the depletion of the conventional shallow oil/gas reservoirs and the increasing demand for oil and gas, deep drilling become more and more essential to extract the oil/gas from deep formations. However, deep drilling faces many complex challenges. One of the complexities is the degradation of polymers and flocculation of bentonite particles, leading to hardly control the rheological and filtration properties of water-based drilling fluids, especially under ultra-high temperature and high pressure (HTHP) conditions. Therefore, an experimental investigation is performed to study how bentonite-hydrothermal carbon nanocomposites will influence the rheological and filtration properties of water-based drilling fluids under ultra-HTHP conditions. Bentonite-hydrothermal carbon nanocomposites are proposed as non-polymer additives to solve the ultra-HTHP challenge in water-based drilling fluid. The nanocomposites are synthesized by facile hydrothermal reaction, in which biomass starch and sodium bentonite are used as the precursor and template, respectively. In this study, the effect of the nanocomposites on the rheology and filtration properties of water-based drilling fluid are investigated before and after hot rolling at 220 °C and 240 °C. The structure characterization indicates that carbon nanospheres can successfully deposit on the bentonite surface after hydrothermal reaction and finally form as nanocomposites. The elemental carbon content, zeta potential and particle size distribution of the nanocomposites could be adjusted according to the reaction conditions. After thermal aging at 220 °C and 240 °C, addition of nanocomposites can improve the rheological properties significantly where a stable and minor change of rheological properties is observed, which is desirable for ultra-HTHP drilling. Regarding filtration control, after adding 1.0 wt% nanocomposite materials, the filtration loss is reduced by 41% and 44% respectively after aging at 220 °C and 240 °C, which is better than the conventional natural materials that lose their function in this case. The identification of microstructure shows that the hydrothermal reaction endows nanocomposites with a unique surface morphology and an improved surface charge density. The interaction between nanocomposites and bentonite particles forms a rigid connection network, which is the main mechanism to facilitate effective rheology and filtration control under ultra-HTHP conditions. The green and facile synthetic routes and environmentally friendly features of the nanocomposites, coupled with the excellent performance in ultra-HTHP rheology and filtration control, indicate that the nanocomposites have a high promise for water-based drilling fluid in ultra-HTHP drilling. Moreover, it provides a new way to design high performance additives with high temperature stability.
4
Kote, Prashant, Magdalen Asare, Sahilkumar Chaudhary, Tim Dawsey, and Ram Gupta. "Flame Retardant Polyurethane Foams Using Vegetable Oil-based polyol." In 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/iefv6816.
Повний текст джерелаАнотація:
Polyurethanes can be used in many applications by modifying their properties via facile methods. Most of the polyurethanes currently used for industrial applications originated from petrochemical-based chemicals. There is a growing demand in industries to use renewable resources for polyurethanes. Vegetable oil-based polyurethanes have shown properties comparable to that of petroleum-based polyurethanes. In this research, sunflower oil was used as a renewable resource for polyurethanes. Rigid polyurethane foams were prepared using sunflower-based polyols. The polyols were synthesized via epoxidation followed by a ring-opening reaction. Epoxy number, hydroxyl number, viscosity, and spectroscopy characterizations confirm the synthesis of bio-polyol. One of the major issues in polyurethanes is their high flammability which was reduced by using flame-retardants. Two flame-retardants using melamine and diphenylphosphinic acid (DPPMA) and a phosphorous‐nitrogen intumescent flame‐retardant (2,2‐diethyl‐1,3‐propanediol phosphoryl melamine, DPPM) were synthesized and used in bio-based polyurethanes. as used as an additive flame retardant. The foams with DPPMA and DPPM showed high closed cell content ( >90%) with a high compression strength of 217 kPa and 208 kPa, respectively. The microstructure analysis of the foams using scanning electron microscopy revealed an even distribution of the pore size. The addition of DPPMA and DPPM in polyurethane foams results in the formation of a protective char layer during the flammability test and reduces the weight loss from 43% to 2.5% and 1.4% and burning time from 70 seconds to 6 seconds and 4.5 seconds, respectively. Our research suggests that sunflower oil could be a potential candidate for the polyurethane industries and DPPMA and DPPM can be used as an effective flame-retardant in these bio-based polyurethane foams.
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Shqau, Krenar, and Amy Heintz. "Mixed Ionic Electronic Conductors for Improved Charge Transport in Electrotherapeutic Devices." In 2017 Design of Medical Devices Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/dmd2017-3454.
Повний текст джерелаАнотація:
Electrotherapeutic devices require an electrode for coupling with the body. The most common electrodes are made of conducting corrosion resistance materials (e.g., TiN, Ir-IrO2, Pt) plus a coupling layer (e.g., electrolyte). The electrode is the location where redox reaction take place between the device and the tissue. As such, it must conduct both electrons and ions. The reactions can be capacitive, involving the charging and discharging of the electrode-electrolyte double layer, or faradaic. Capacitive charge-injection is more desirable than faradic charge-injection because no chemical species are created or consumed during a stimulation pulse. Most noble metal based electrodes are faradic or pseudo-capacitive, which can lead to performance changes over time. In addition, under the high rate of charge injection and high current density conditions of a neuromuscular stimulation pulse, access to all the accessible charges is limited by the interfacial resistance and low surface area at the electrode [1]. A particularly critical point is the passage of current between the surface of the skin and the electrical contact connected by wire to the device, which requires a low stable resistance that does not vary with time, humidity [2]. We have developed new hybrid mixed-ionic-electronic conductors (MIECs) that have the potential to overcome these deficiencies. The MIECs are an interconnected network of electrical and ionic conductors in an elastomeric matrix that provide: (1) high surface area for efficient capacitive charge-discharge; (2) high ionic conductivity for low interfacial resistance; (3) low ohmic resistance; and (4) excellent flexibility and toughness. Carbon nanotubes (CNTs) are the electrical conductors in the MIEC and hyaluronic acid (HA), along with moisture and ions, is the ionic conductor. Unlike the current state-of-the-art, conducting noble metals, this system exhibits good mechanical properties, high conductivity (up to 3000 mS/cm), high moisture retention (up to 100wt%) and high ion mobility, leading to facile electrode kinetics. This simple yet efficient system is promising for the fabrication of a variety of high performance flexible electrodes.