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Showing 1 to 17 of 17 for “"stereochemical course"”.
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Stereochemical Course of the Tandem [4+2]/[3+2] Cycloaddition of Nitroalkenes
The [4+2] cycloaddition of nitrobutene was further examined with both experimental and theoretical studies. Small, soft Lewis acids (such as Me 3Al) promote endo cycloaddition with the vinyl ether reacting in an s-trans conformation. Most other Lewis acids favor exo cycloaddition due either to …
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On the stereochemical course of the chlorine-38 for chlorine substitution in diastereomeric and enantiomeric compounds
… in solution. It was found that the stereochemical course of the substitution reaction exhibits a strong dependence on the concentration and nature of the solvent added when the diastereomeric compounds were used as substrate. Similar results with a lesser degree of solvent dependence …
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I. Catalyst development in asymmetric phase transfer catalysis employing QSAR methods II. Computational investigations on the stereochemical course of the addition of allylsilanes to aldehydes
Part I of this dissertation describes the investigation in APTC employing a chemoinformatic analysis of the alkylation of a protected glycine imine with libraries of enantiomerically enriched quaternary ammonium ions. The synthesis of the quaternary ammonium ions follows a diversity oriented …
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Chlorine-38 for chlorine substitution in geometric and diastereomeric compounds: mechanism and stereochemistry
In order to determine how solvents control the stereochemical course of the hot substitution reactions, the stereochemistry of the energetic ³⁸Cl for Cl was studied in diastereomeric 1,2-dichloro-1,2-difluoroethane and the geometric isomers of 1,2-dichlorohexa-fluorocyclobutane. In each system, the …
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Structure and Biosynthesis of the Diterpene Hydrocarbon, Casbene
The stereochemical course of the enzyme catalyzed cyclization of geranylgeranyl pyrophosphate (GGOPP) to casbene, (1S,14R)-(E,E,E)-3,7,11,15,15-pentamethylbicyclo{14.1.0}pentadeca-2,6,10-triene, was defined in the castor bean plant (Ricinus communis L.,) by resolving the four stereochemical …
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Investigations of transition state geometry in the intramolecular aldol reaction and the intramolecular reaction of allylsilanes with aldehydes
… counterions, solvents, and additives have on the stereochemical course of cyclization in these models. These models are the first to provide data concerning the factors which influence the preference for an open versus closed transition state in the absence of extraneous steric bias. Results …
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Extension of Chromatographically - Derived Molecular Recognition Concepts to Stereoselective Reactions and Transformations
… were used to study the stereochemical course of the coupling of chiral acids and chiral amines.
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Stereochemistry of the Allene-Forming Cycloelimination of 4-Diazo-3,5-Diethyl-3,5-Dimethyl-1-Pyrazoline
… this investigation was the determination of the stereochemical course of the decomposition of diazopyrazoline 1a to 3,5-dimethyl-3,4-heptadiene (2). To achieve this goal, a stereospecific synthesis of 1a which would permit its optical resolution was devised. Cyclization of tosylhydrazine and …
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Stereoselective alkylations and rearrangements of chiral phosphonic and phosphinic acid derivatives
The stereochemical course of carbon migration from phosphorus to nitrogen and oxygen were investigated. Optically active ($\geq$99.9% e.e.) phosphonic and phosphinic azides were prepared and photolyzed in methanol to effect the phosphorus analogues of the carbonyl-Curtius rearrangement. These …
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On the Stereochemistry of Allylmetal-Aldehyde Condensations (Allyltrimethylsilane, Allyltributylstannane, Homoallylic Alcohols)
The stereochemical course of the intramolecular allylmetal-aldehyde condensation of allylsilane 3a, allylstannane 3b, and pentadienylsilane 6 has been investigated. A modest preference for the syn isomer 4 arising from a synclinal orientation of double bonds was observed with the Lewis acid …
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Investigations of Bicyclo(3.1.1)heptane Terpenes in Higher Plants: Stereochemistry of Pinene Biosynthesis and Isolation of Bergamoten-12-Oic Acids
… and ($-$)-$\beta$-pinene (cyclase II). The stereochemical course of these cyclizations at the gem dimethyl position of the pinene products was investigated. (6E)- (8-$\sp3$H) GPP was synthesized in ten steps from geraniol and incubated with each cyclase to afford (+)- ($\sp3$H) …
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Mechanistic Studies on Memory of Chirality Alkylations of 1,4-Benzodiazepin-2-ones & Structure-based Design of Insecticidal AChE Inhibitors for Malaria Mosquito, Anopheles gambiae
… in the intermediate; trapping then captures the stereochemical information, and generates a new stereogenic center with high fidelity. We experimentally and computationally studied the highly retentive deprotonation/alkylations of 1,4-benzodiazepin-2-ones (BZDs) that rely upon this strategy. We …
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Synthesis, crystallography and biological activity of myo-inositol phosphates
… which would be useful for the analysis of the stereochemical course of phosphate hydrolysis catalysed by inositol monophosphatase.
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Improving synthetic efficiency through C—H activation
… organometallic intermediate and influences the stereochemical course of the catalytic process. Additionally, this work establishes that the asymmetric branched allylic oxidation reaction can be combined with other enantioselective transformations to afford enantiopure, polyoxygenated allylic …
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METHODOLOGY DEVELOPMENT OF N-SULFINYL METALLOENAMINES AND ASYMMETRIC TOTAL SYNTHESIS OF (+)-EPIIBOGAMINE
… affecting stereoselectivity revealed that stereochemical erosion occurred using SnCl4 combined with LiHMDS, but not with NaHMDS or KHMDS. A (Z)-metallodienamine with metal chelated transition state was proposed and supported by DFT calculations to rationalize the stereochemical course of …
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The development of palladium-catalyzed cross-coupling reactions of allylic silanolate salts with aromatic bromides
… can rationalize all of the observed trends. The stereochemical course of palladium-catalyzed cross-coupling reactions of an enantioenriched, alpha-substituted, allylic silanolate salt with aromatic bromides was determined. The allylic silanolate salt was prepared in high geometrical (Z/E, 94:6) …