Academic literature on the topic 'Phosphonique acide derive'
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Journal articles on the topic "Phosphonique acide derive"
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McGall, Glenn H., and Robert A. McClelland. "Hydrolysis of a monocyclic oxyphosphorane containing a five-membered ring." Canadian Journal of Chemistry 69, no. 12 (December 1, 1991): 2075–83. http://dx.doi.org/10.1139/v91-300.
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A kinetic study is reported for the hydrolysis of 2,2-diphenyl-2-methoxy-1,3,2-dioxaphospholane 1. This phosphorane exists in aqueous solution in a pseudo acid–base equilibrium with an observable phosphonium ion, the ring-opened (2′-hydroxyethoxy)diphenylmethoxyphosphonium ion 5. The equilibrium constant Ka ([1][H+]/[5]) is 9 × 10−9, values determined by kinetic and spectroscopic methods being in good agreement. This phosphonium ion is, however, not involved in the overall hydrolysis reaction, which proceeds via the thermodynamically less stable cyclic five-membered phosphonium ion derived by loss of the exocyclic methoxy group from the phosphorane, the 2,2-diphenyl-1,3,2-dioxaphospholan-2-ylium ion 6. This route for the overall hydrolysis is established by analysis of the products, and by the observation that the rate constant for the disappearance of 5 in acid solutions is 40 000 times greater than that for an analog that differs only in not being able to cyclize, the (2′-methoxyethoxy)diphenylmethoxyphosphonium ion 7. At all pH, the phosphorane 1 and the ring-opened phosphonium ion 5 exist in equilibrium, and the rate-limiting step in the overall hydrolysis is the cleavage of the exocyclic methoxy group to give the cyclic phosphonium ion 6, which is rapidly converted to products by reaction with water. The actual equilibration reaction involving 1 and 5 cannot be observed at any pH, even with stopped-flow spectroscopy. The non-catalyzed ring closure of the phosphonium ion 5 reforming the phosphorane 1 occurs with a rate constant of 200–500 s−1, corresponding to an effective molarity of (2–5) × 107 M for the intramolecular hydroxy group in this reaction. The rate-limiting exocyclic cleavage is assisted by H+, with a very large rate constant 2 × 109 M−1 s−1. Catalysis by general acids is also observed. The Brønsted plot has a slope α of 1.0 for the weaker acids, with a break for acids with pKa < 3. This "Eigen"-type behavior is proposed to arise from a transition state with little phosphonium ion character, in which the proton is almost completely transferred for the weaker acids. Key words: phosphorane, phosphate, phosphonium, hydrolysis.
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Waked, Alexander E., Rouzbeh Ostadsharif Memar, and Douglas W. Stephan. "Nitrogen-Based Lewis Acids Derived from Phosphonium Diazo Cations." Angewandte Chemie 130, no. 37 (July 9, 2018): 12110–14. http://dx.doi.org/10.1002/ange.201804183.
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Waked, Alexander E., Rouzbeh Ostadsharif Memar, and Douglas W. Stephan. "Nitrogen-Based Lewis Acids Derived from Phosphonium Diazo Cations." Angewandte Chemie International Edition 57, no. 37 (July 9, 2018): 11934–38. http://dx.doi.org/10.1002/anie.201804183.
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Demadis, Konstantinos D., Melina Preari, and Ioanna Antonakaki. "Naturally derived and synthetic polymers as biomimetic enhancers of silicic acid solubility in (bio)silicification processes." Pure and Applied Chemistry 86, no. 11 (November 1, 2014): 1663–74. http://dx.doi.org/10.1515/pac-2014-0705.
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Abstract Numerous publications report the existence of intracellular “Si” storage pools in diatoms representing intracellular concentrations of ca. 19–340 mM depending on the species. “Si” storage pools in diatom cells, if present, are supposed to accumulate “Si” for the production of new valves. The accumulated “Si” is then transported into the silicon deposition vesicle (SDV) where the new cell wall is synthesized. Interestingly, the reported concentrations of intracellular “Si” within the storage pool sometimes strongly exceed the solubility of monosilicic acid (ca. 2 mM pH <9). Various types of “Si” storage pools are discussed in the literature. It is usually assumed that “Si” species are stabilized by the association with some kind of organic material such as special proteins, thus forming a soluble silicic acid pools inside the cells. In an effort to mimic the above phenomenon, we have used a variety of neutral or cationic polymers that stabilize two soluble forms of “Si,” silicic and disilicic acids. These polymers include amine-terminated dendrimers, amine-containing linear polymers (with primary, secondary or tertiary amines), organic ammonium polymers, polyethylene glycol (PEG) neutral polymers, co-polymers (containing neutral and cationic parts) and phosphonium end-grafted PEG polymers. All the aforementioned polymeric entities affect the rate of silicic acid polycondensation and also the silica particle growth. Synergistic combinations of cationic and anionic polymers create in situ supramolecular assemblies that can also affect the condensation of silicic acid. Possible mechanisms for their effect on the condensation reaction are presented, with an eye towards their relevance to the “Si pools,” from a bioinspired/biomimetic point of view.
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Walęcka-Kurczyk, Alicja, Krzysztof Walczak, Anna Kuźnik, Sebastian Stecko, and Agnieszka Październiok-Holewa. "The Synthesis of α-Aminophosphonates via Enantioselective Organocatalytic Reaction of 1-(N-Acylamino)alkylphosphonium Salts with Dimethyl Phosphite." Molecules 25, no. 2 (January 18, 2020): 405. http://dx.doi.org/10.3390/molecules25020405.
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α-Aminophosphonic acids are phosphorus analogues of α-amino acids. Compounds of this type find numerous applications in medicine and crop protection due to their unique biological activities. A crucial factor in these activities is the configuration of the stereoisomers. Only a few methods of stereoselective transformation of α-amino acids into their phosphorus analogues are known so far and all of them are based on asymmetric induction, thus involving the use of a chiral substrate. In contrast, we have focused our efforts on the development of an effective method for this type of transformation using a racemic mixture of starting N-protected α-amino acids and a chiral catalyst. Herein, a simple and efficient stereoselective organocatalytic α-amidoalkylation of dimethyl phosphite by 1-(N-acylamino)alkyltriphenylphosphonium salts to enantiomerically enriched α-aminophosphonates is reported. Using 5 mol% of chiral quinine- or hydroquinine-derived quaternary ammonium salts provides final products in very good yields up to 98% and with up to 92% ee. The starting phosphonium salts were easily obtained from α-amino acid derivatives by decarboxylative methoxylation and subsequent substitution with triphenylphosphonium tetrafluoroborate. The appropriate self-disproportionation of enantiomers (SDE) test for selected α-aminophosphonate derivatives via achiral flash chromatography was performed to confirm the reliability of the enantioselectivity results that were obtained.
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Suganuma, Yuta, Shun Saito, and Yuichi Kobayashi. "Synthesis of 8-HEPE and 10-HDoHE in both (R)- and (S)-Forms via Wittig Reactions with COOH-Ylides." Synlett 30, no. 03 (January 10, 2019): 338–42. http://dx.doi.org/10.1055/s-0037-1611976.
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Wittig reactions using carboxy (CO2H) ylides derived from a carboxylic phosphonium salt and NaN(TMS)2 (NaHMDS) in a 1:1 ratio were applied to the synthesis of 8-HEPE and 10-HDoHE, which are metabolites of eicosapentaenoic acid and docosahexaenoic acid, respectively. The attempted Wittig reaction of 3-(TBS-oxy)pentadeca-4E,6Z,9Z,12Z-tetraenal with the carboxy ylide (2 equiv) derived from Br– Ph3P+(CH2)4CO2H and NaHMDS (1:1) competed with the elimination of the TBS-oxy group at C3 to give a mixture of the Wittig product and the elimination product in 45–50% and 30–40% yields, respectively. The elimination was suppressed completely by using three equiv of the carboxy ylides in THF/HMPA (7–8:1), and the subsequent desilylation gave 8-HEPE in (R)- and (S)-forms. Similarly, both enantiomers of 10-HDoHE were synthesized.
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McGall, Glenn H., and Robert A. McClelland. "Kinetics and mechanism of the hydrolysis of a (5,6)-spirophosphorane. Thermodynamics of the hydrolysis of cyclic five-membered and six-membered phosphonium ions." Canadian Journal of Chemistry 69, no. 12 (December 1, 1991): 2064–74. http://dx.doi.org/10.1139/v91-299.
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The cyclic five-membered phosphonium ion 2b (2-(2′-hydroxyethoxy)-2-phenyl-1,3,2-dioxaphospholan-2-ylium) derived from ring-opening of the (5,5)-spirophosphorane 1b (5-phenyl-1,4,6,9-tetraoxa-5-phosphaspiro[4,4]nonane) has been observed in neat CF3SO3H and at >85% H2SO4. The cation undergoes hydrolysis in the latter solutions, and an extrapolation has been carried out to obtain an estimate for reactivity in 100% water. Hydrolysis rate constants for phenyltrialkoxyphosphonium ions in water are 107, 100, and 5 × 10−3 s−1 for cyclic five-membered, cyclic six-membered, and acyclic derivatives respectively; these show an excellent correlation with rate constants for a similar series of phosphate esters. An investigation of the hydrolysis of the (5,6)-spirophosphorane 5 (5-phenyl-8,8-dimethyl-1,4,6,10-tetraoxa-5-phosphaspiro[4,5]decane) provides a clue as to the origins of these rate differences. This phosphorane can in principle hydrolyze via two isomeric cyclic phosphonium ions, the six-membered 14 and the five-membered 15. The former is thermodynamically more stable, being the only cation observed under equilibrating conditions of strong acid. However, the hydrolysis of the spirophosphorane, as well as the hydrolysis of fully formed 14, channels through the cyclic five-membered 15. A thermodynamic breakdown reveals that the 9.5 kcal mol−1 difference in activation free energy for the hydrolysis of five- and six-membered cyclic phosphonium ions is due to a combination of a higher free energy (2.5–4.5 kcal mol−1) for the five-membered cation, and a lower free energy (7–5 kcal mol−1) for the pentacoordinate transition state with the five-membered ring. This analysis also shows that a (5,6)-spirophosphorane is 6–8 kcal mol−1 more stable than a (6,6)-spirophosphorane. Thus, a five-membered ring has a significant stabilizing effect on a pentacoordinated phosphorus structure. The accelerated hydrolysis of cyclic phosphonium ions and phosphate esters with five-membered rings is caused by a combination of this stabilizing effect in the transition state and a destabilizing effect in the ground state associated with ring strain. Key words: phosphorane, hydrolysis, phosphate, phosphonium.
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Litera, Jaroslav, Jan Weber, Ivana Křížová, Iva Pichová, Jan Konvalinka, Martin Fusek, and Milan Souček. "Peptide Inhibitors of Aspartic Proteinases with Hydroxyethylene Isostere Replacement of Peptide Bond. II. Preparation of Pseudotetrapeptides Derived from Diastereoisomeric 5-Amino-2-benzyl-4-hydroxy-6-phenylhexanoic Acids." Collection of Czechoslovak Chemical Communications 63, no. 4 (1998): 541–48. http://dx.doi.org/10.1135/cccc19980541.
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Twelve pseudotetrapeptides, Boc-NHCH(CH2Ph)CH(OH)CH2CH(CH2Ph) CO-Xaa-Phe-NH2 9-11, were prepared by [(benzotriazol-1-yl)oxy]tris(dimethylamino)phosphonium hexafluorophosphate-mediated couplings of diastereoisomeric O-silylated (2R or 2S,4R or 4S,5S)-2-benzyl-5-(tert-butoxycarbonyl)amino-4-hydroxy-6-phenylhexanoic acids 1 with dipeptides H-Xaa-Phe-NH2 (Xaa = Gln, Glu(OBzl) or Ile) 3-5, followed by O-deprotection. Pseudotetrapeptides 9-11 were tested for inhibition of aspartic proteinases secreted by Candida albicans and C. tropicalis. The level of inhibition of both yeast proteinases was very low, contrasting with the nanomolar IC50 values obtained for inhibition of HIV-1 proteinase.
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Quitadamo, Alessia, Valérie Massardier, and Marco Valente. "Interactions between PLA, PE and wood flour: effects of compatibilizing agents and ionic liquids." Holzforschung 72, no. 8 (July 26, 2018): 691–700. http://dx.doi.org/10.1515/hf-2017-0149.
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AbstractThe differences in hydrophilicity are a main drawback for wood polymer composites (WPCs). This work aims at compatibilizing bio-derived poly(lactic acid) (PLA), high density polyethylene (PE) and wood fibers (WFs) with either functional PEs [PE-graft-maleic anhydride (MA) (Polybond 3029) or random copolymer of ethylene and glycidyl methacrylate (PE-g-GMA) (Lotader AX8840)] or trihexyl(tetradecyl)phosphonium bistriflamide ionic liquid (IL). The interactions and possible chemical reactions between PLA and functional PE or IL were studied including their mechanical properties. PE-g-GMA significantly increased elongation at break of PLA. According to scanning electron microscopy (SEM), the latter also displays good compatibility with WF. Addition of IL plastifies PLA without degrading it and improves the thermal stability of WF.
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Zhang, Jiaxing, Dongdong Cao, Hongyu Wang, Gang Zhao, and Yongjia Shang. "Enantioselective desymmetrization of meso-aziridines with aromatic thiols catalyzed by chiral bifunctional quaternary phosphonium salts derived from α-amino acids." Tetrahedron 71, no. 12 (March 2015): 1785–91. http://dx.doi.org/10.1016/j.tet.2015.02.001.
Full textDissertations / Theses on the topic "Phosphonique acide derive"
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Haelters, Jean-Pierre. "Synthèse de dérivés phosphono-indoliques-benzofuranniques et -pyrroliques à partir d'hydrazones phosphonates." Brest, 1987. http://www.theses.fr/1987BRES2002.
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Des derives phosphonoindoliques sont prepares par cyclisation d'arylhydrazones d'oxoalkylphosphonates selon fisher et par cyclodeshydratation d'arylamino-1 et arylamino-3 oxo-2 propylphosphonates selon bischler. Des indolyl-2 et indolyl-3 phosphonates, des indolylmethyl-2 et des indolylmethyl-3 phosphonates diversement substitues et leurs acides phosphoniques correspondants sont decrits. Toutes structures sont analysees par rmn **(1)h, **(31)p et 1**(3)c. L'analogue phosphore de l'intermediaire a aussi ete prepare. L'extention de la reaction de bischler aux aryloxycetones permet d'atteindre des benzofuryl-2 phosphonate et de benzofurylmethyl-3 phosphonates. Deux nouveaux reactifs sont utilises pour acceder aux arylaminocetones et aux aryloxycetones : les chloro-1 et chloro-3 methoxycarbonylhydrazono-2 propyl-phosphonates de diethyle, composes qui, traites en milieu basique, donnent des azoenes qui additionnent les anilines et les phenols. Ces azoenes additionnent aussi les carbanions, notamment les carbanions derives de cetones pour conduire, apres hydrolyse soit a des derives du pyrrole, soit a des dioxy-2, -5-alkylphosphonates precurseurs de cyclopentenones selon wittig-horner
Book chapters on the topic "Phosphonique acide derive"
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Taber, Douglass F. "The Trost Synthesis of (-)-Pseudolaric Acid B." In Organic Synthesis. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199965724.003.0085.
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(-)-Pseudolaric acid B 3, isolated from the bark of the golden larch Pseudolarix kaempferi, shows potent antifungal activity. A key step in the total synthesis of 3 described (J. Am. Chem. Soc. 2008 , 130 , 16424) by Barry M. Trost of Stanford University was the free radical cyclization of 1 that established the angular ester and the trans ring fusion of 2 and thus of 3. To prepare the bicyclic skeleton of 1, the authors envisioned the Rh-mediated intramolecular addition of the alkyne of 11 to the alkenyl cyclopropane. The acyclic centers of 11 were established by Noyori hydrogenation of (equilibrating) racemic 4. One enantiomer reduced much more quickly than the other, leading to 5. The absolute configuration of the cyclopropane was set by Charette cyclopropanation of the monosilyl ether of the inexpensive diol 8. The two components were then coupled using a Corey-Schlosser protocol. Alkylation of the ylide 10 with 7 gave a new phosphonium salt, which in situ was deprotonated and condensed with the aldehyde 9 . The resulting betaine was deprotonated and quenched, then exposed again to base to give the trans alkene 11. It is important in this procedure to use PhLi as the base, because the alkyl lithium can displace the alkyl group on phosphorus. The product from Ru-catalyzed cyclization was the expected 1,4-diene 12 . Fortunately, it was found that TBAF desilylation led to concomitant alkene migration, to give the more stable conjugated diene 13. Selective epoxidation of the more electron-rich alkene fol lowed by exposure to strong base then delivered 14 , with the requisite angular oxygenation established. Pseudolaric acid B 3 would be derived from cyclization of the selenocarbonate of a tertiary alcohol. In fact, however, attempted cyclization of such selenocarbonates led only to decarboxyation and reduction. Even with the selenocarbonate 1 prepared from the secondary alcohol, the cyclization to 2 required careful optimization, including using not AIBN but azobis(dicyclohexylcarbonitrile) as the radical initiator. Acetylide addition to the ketone 15 could be effected with high diastereocontrol, but lactone construction proved elusive. Alkaline conditions led quickly to addition of the angular hydroxyl to the activated alkene in the seven-membered ring.
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Taber, Douglass. "The Keck Synthesis of Epothilone B." In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0101.
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The total synthesis of Epothilone B 4, the first natural product (with Epothilone A) to show the same microtubule-stabilizing activity as paclitaxel (Taxol®), has attracted a great deal of attention since that activity was first reported in 1995. The total synthesis of 4 devised (J. Org. Chem. 2008, 73, 9675) by Gary E. Keck of the University of Utah was based in large part on the stereoselective allyl stannane additions (e.g. 1 + 2 → 3 ) that his group originated. The allyl stannane 2 was prepared from the acid chloride 5. Exposure of 5 to Et3N generated the ketene, that was homologated with the phosphorane 6 to give the allene ester 7. Cu-mediated conjugate addition of the stannylmethyl anion 8 then delivered 2. The silyloxy aldehyde 1 was prepared from the ester 9 by reduction with Dibal. Felkincontrolled 1,2-addition of the allyl stannane 2 established the relative configuration of the secondary alcohol of 3, that was then used to control the relative configuration of the new alcohol in 10. Addition of the crotyl borane 12 to the derived aldehyde 11 also proceeded with high diastereocontrol. The other component of 4 was prepared from the aldehyde 14. Enantioselective allylation, by the method the authors developed, delivered the alcohol 16. The Z trisubstituted alkene was then assembled by condensing the aldehyde 17 with the phosphorane 18. Dibal reduction of the product lactone 19 gave a diol, the allylic alcohol of which was selectively converted to the chloride with the Corey-Kim reagent. Hydride reduction then delivered the desired homoallylic alcohol, that was converted to the phosphonium salt 21. Condensation of 21 with 13 gave the diene, that was carried on to Epothilone B 4. The synthesis of Epothilone B 4 as originally conceived by the authors depended on ring-closing metathesis of the triene 22. They prepared 22, but on exposure to the second-generation Grubbs catalyst it was converted only to 23. The authors concluded that the trans acetonide kept 22 in a conformation that did not allow the desired macrocyclization.