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Showing 1 to 19 of 19 for “"chiral catalyst"”.
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Asymmetric synthesis of amines by the catalytic enantioselective additions of hydrazoic acid to ketenes
The development of a planar-chiral catalyst for the enantioselective additions of HN3 to hindered ketenes was investigated. It was demonstrated that a new planar-chiral catalyst (1.5) is an excellent catalyst for the enantioselective addition of HN3 to hindered ketenes, en route to enantioenriched …
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Asymmetric cyclopropanation via catalysts incorporating the 1,4-diol ligands and the newly designed dioxaborolane /
… new methodology for the asymmetric synthesis of chiral organic compounds is a major focus in modem organic chemistry. The use of chiral catalysts is replacing chiral auxiliaries as a new tool for synthetic chemists. An efficient chiral catalyst allows for large quantities of optically active …
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Lewis Base Catalyzed Aldol Additions of Chiral Silyl Enol Ethers and Total Synthesis of Rk-397
The double diastereodifferentiation in chiral Lewis base catalyzed aldol additions was examined using chiral silyl enol ethers derived from hydroxyisobutyrate and hydroxybutyrate. Trichlorosilyl enolates derived from the chiral methyl and ethyl ketones were subjected to the Lewis base catalyzed …
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Asymmetrischer katalytischer Phenyltransfer zur Synthese von Diarylmethanolen und Diarylmethylaminen
… was developed, employing catalytic amounts of a chiral catalyst precursor. The results of synthetic studies and investigations in order to reveal the nature of the active species in the catalysis by means of low-temperature-NMR- and IR-spectroscopic methods are presented. Previous syntheses of …
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Bicyclische Triazoliumsalze als Präkatalysatoren in der asymmetrischen Benzoin- und Acyloinkondensation und asymmetrische Synthese von Oxazolidin-2-onen
… salt and its application as an efficient chiral catalyst in the form of the corresponding Wanzlick carbene in the asymmetric variant of the benzoin condensation is described. The chiral bicyclic triazolium salt is currently the most efficient precatalyst for the asymmetric benzoin …
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Synthesis of Chiral Surfactants for Enantioselective Organic Synthesis.
… step of the synthesis of the hydrocarbon-based chiral surfactant <b>(2)</b> involved the methylation of (S)-leucinol to give (2S)-N-hexadecyl-N,N-dimethyl-(1-hydroxy-4-methyl-1-pentyl)-2-ammonium bromide (2.92g, 67%). The chiral surfactant was synthesized by reacting …
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Asymmetric hydrogenation of unfunctionalized trisubstituted and tetrasubstituted olefins
A highly reactive chiral catalyst for the asymmetric hydrogenation of aryl trisubstituted olefins was generated by combining the complex (EBTHI)MMe2 (EBTHI = ethylenebistetrahydroindenyl, M = Ti, Zr) with [PhMe2NH]+[(BC6F5)4]- under a hydrogen atmosphere. A number of unfunctionalized trisubstituted …
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Homochiral Crystals for Selective Synthesis
… with enantiomeric excesses up to 90 %. Three chiral Ru(II) complexes with bidentate sulfide ligands were prepared and all three crystallized as conglomerates. They were used in absolute asymmetric synthesis and oxidized enantioselectively. The oxidations resulted in a selectivity of > 98% …
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Katalytische, enantioselektive Synthesen von Diarylmethanolen und Allylalkoholen
… reactions to aldehydes for the synthesis of chiral diarylmethanols were developed. Diarylmethanols are important intermediates for the synthesis of pharmaceutically active compounds. In the foregoing research, it was found that, in presence of an appropriate catalyst, diarylmethanols could be …
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Stereoselective monoalkyl diazene synthesis for mild reductive transformations : direct synthesis of densely substituted pyridines and pyrimidines
… of optically active substrates or the use of chiral catalyst systems for the reduction of racemic and prochiral substrates. Sensitive substrates are reduced in a highly selective manner. III. Direct Synthesis of Pyridine Derivatives A single-step conversion of various N-vinyl and N-aryl amides …
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Heterogeneous asymmetric epoxidation of cis-ethyl cinnamte over Jacobsen's catalyst immobilized in inorganic porous materials
… is one of the most relevant methods. However the chiral catalyst, a Manganese(lll) salen complex coexists with the reaction products in one unique phase. This makes it difficult to separate the reaction products and catalyst reusability, two key features in the drive to develop an industrial …
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Indium complexes and their role in the ring-opening polymerization of lactide
The synthesis and characterization of a series of chiral indium complexes bearing a tridentate NNO ligand are reported. The ligand 2-[[[(dimethylamino)cyclohexyl]amino]methyl]- 4,6-bis(tert-butyl) phenol (H₂NNO) was synthesized via a previously published procedure and bound to indium by both a …
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The Kinetic Resolution of Secondary Alcohols Through A Tandem Enantioselective Silylation and the Synthesis of Bis(Oxazolidinyl)Pyridine Metal-Organic Complexes
… reaction. The design of a bi-functional organic chiral catalyst, which comprises of a Lewis base acetate anion paired with a chiral quaternary ammonium cinchona alkaloid, is discussed. We found that when the addition of a silyl ketene acetyl to benzaldehyde is catalyzed with our bi-functional …
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Gold compact disc appended Tröger’s base scaffolds as MALDI-TOF biodetection probes
… V-shaped structure with C2 symmetry containing a chiral, hydrophobic cleft creating an angle of 90˚. For many years its chiral cleft has been utilised for the stationary phase of chiral HPLC columns, a chiral resolving agent and as a chiral catalyst. Over the past 30 years it has been reported …
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Asymmetrische Synthese von cyclischen allylischen S-tert-Butylsulfonen : Pd-katalysierte kinetische Racematspaltung racemischer Allylcarbonate und zur Struktur chiraler, cyclischer allylischer Alpha-tert-Butylsulfonyl-Carbanionen
… asymmetric substitution in presence of a chiral bisamide-bisphosphane-Ligand. The sulfones were formed from the corresponding racemic carbonates and lithium-tert-butylsulfinate in a two phase system composed of dichlormethane and water at 0 °C containing THAB as a phase transfer catalyst …
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Organoselenium redox-catalyzed, enantioselective syn-difunctionalization of alkenes
… selenofunctionalization reactions with chiral, enantioenriched organoselenium electrophiles, as well as the growing field of selenofunctionalization-deselenenylation reactions catalyzed by achiral organoselenium reagents. Finally the intersection of these two approaches, enantioselective …
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Isomerization-Locked Alkene Analogues of Xaa–Pro Dipeptides in the Proteins Collagen and Bora
… (Z)-fluoro-alkene Gly–Pro isostere. We used the chiral catalyst, L-Thr, for asymmetric aldol addition to cyclopentanone, which inadvertently enhanced the yield of the wrong enantiomer, in contrast with aldol addition to cyclohexanone. A Mg2+-promoted Horner-Wadsworth-Emmons reaction afforded the …
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Novel Chiral Diamines and (S)-6-Chloronicotine Derivatives as Catalysts for Asymmetric Synthesis
… are highly desirable. Asymmetric synthesis using chiral compounds has become the preferred way to make enantiopure material. For example, selectively synthesizing secondary alcohols that are ubiquitous in natural products and pharmaceuticals can be achieved through the catalytic asymmetric …
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The synthesis of N-substituted ferrocenes and CH activation towards the synthesis of Organosilanols
… ortho-silylated product. The synthesis of planar-chiral ferrocene-based organosilanols was also described. High enantioselectivities and yields of up to 91 and 87%, respectively, have been achieved in collaboration with Frank Schmidt using both zinc and boron-based aryl sources. Although silanols …