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Showing 1 to 20 of 57 for “"steric bulk"”.
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Development of an Improved Synthesis of S-D-Ribosyl-L-Homocysteine (SRH) and Progress Toward SRH Analogs Modified at the C3 Position
… the synthesis of SRH analogues with increased steric bulk installed through use of a stereoselective anti-Mannich reaction. SRH analogues with increased steric bulk are hypothesized to act as inhibitors of LuxS – with the ultimate goal decreasing the amount of AI-2 in the environment and …
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Surface Modification and Controlled Assembly of Molecular Materials
… of the crystals and that the surface and bulk properties had potential to be modified independently. Copper-pyridine crystals were studied to determine how the steric bulk on pyridine influenced the pyridine coordination to copper. It was found that as the steric bulk of the pyridine …
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N-Ligand Stabilized Lanthanide Complexes
… overall results emphasize the importance of the steric bulk of the applied ligands to stabilize various lanthanide complexes with a distinct reactivity. To highlight and compare the steric bulk of an aminopyridinato with those of amidinate ligands mononuclear seven coordinated complexes of …
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Scope of enantioselective reduction of imines with trichlorosilane
… (68-85 %), the enantioselectivity depended on steric bulk in proximity to the nitrogen, steric bulk improved the enantioselectivity (up to 78 % ee), probably due to thwarting the coordination of the nitrogen to HSiCl3. 2. Aromatic heterocycles containing sulfur – sulfur in the ring was …
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Early Transition Metal Complexes Stabilized by Bulky Aminopyridinato Ligands
… of electrophilicity of the metal centre, the steric bulk of the applied ligands, and the route of syntheses. Trialkyltantalum complexes were synthesized by salt elimination or toluene elimination by reacting the corresponding lithiated ligand with trialkyltantalum dichloride or the …
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Development of asymmetric catalysts based on planar-chiral [pi]-complxes of nigrogen heterocycles with iron
… into nucleophilic catalysts while minimizing steric bulk in the vicinity of the nucleophilic atom was explored. Because many of the most effective nucleophilic catalysts have planar structures (e.g., 4- (dimethylamino)pyridine, pyridine, and imidazole), we were interested in the synthesis of …
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Discrete polyene oligomer synthesis and related polymer characterization : (Appendix I: Reduced tungsten dimeric compounds)
… been established based on solvent polarity and steric bulk at the ester functionality. Extrapolation of the data here yields pertinent information to the polymer field since the oligomers mimic polymeric materials made by RCMP of 1,6-heptadiyne substrates that are fully five-membered ring …
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Preparing Biological surfaces with well defined density and spatial distribution
… done using supramolecular interactions and the steric bulk of dendrons (to achieve the spacing). In order to do this, the axle component of a pseudorotaxane complex would have to be synthesised and absorbed to the surface via covalent bonding (chemisorption) to create a self-assembled monolayer …
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Reductive elimination of alkylamines and ethers: reactions of bisphosphine-ligated palladium(II) complexes
… reaction, and is favored by the increased steric bulk of the neopentyl ligand. We also investigated azametallacyclic palladium complexes with a norbornyl hydrocarbyl ligand, and observed reductive elimination occurs to form a norbornyl indoline product. We found that the yield was slightly …
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Synthesis of Group (lV) Transition Metal Complexes and their Applications as Catalysts for Ethylene Polymerization
… metallocene dichloride complexes bearing bulky alkoxy substituents on indenyl moieties and the investigation of their potential as ethylene polymerization catalysts. Indenyl compounds bearing bulky alkoxy substituents can be prepared by refluxing phenol or naphthol derivatives with …
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Investigations into cyclopropanation and ethylene polymerization via salicylaldiminato copper (II) complexes
… test reaction for homogeneous catalysts. Sterically bulky salicylaldimine (SAL) ligands should select for the ethyl trans-2-phenylcyclopropanecarboxylate diastereomer. Steric bulk poorly influences trans:cis ratios. Salicylaldiminine ligands do not posses the correct symmetry to affect …
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Palladium(II)-Catalysed sp 3 C–H Functionalisation of Hindered Amines and its Application in Synthesis of Astemizole Analogues
… hindered secondary amines that facilitates a sterically promoted palladium-catalysed C–H activation. A range of functional groups are shown to be compatible with this catalytic process, and with exclusive regioselectivity for the terminal ethyl sp 3 C–H in most cases. This method allows an …
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Synthesis and utilization of guanidine catalysts for applications directed towards the preparation of butenolide and modified amino acid derivatives
… enantioselectivity by increasing backbone steric bulk.
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Diastereoselective α-Alkylation of Chiral β-Borylated Esters
… that possess varying degrees of substitution and steric bulk. Results show that the reaction is syn-selective and provides yields of up to 60%, with diastereomeric ratios as high as (9.7:1). Additionally, alkylation products from bulkier tert-butyl esters provide higher DR values compared to those …
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Functional Supramolecular Hydrogels Mediated by Host-Guest Chemistry
… combine both electronic repulsion and increasing steric bulk. The resultant hydrogels are characterised by rheology, tensile testing, nuclear magnetic resonance spectroscopy, small-angle x-ray scattering and differential scanning calorimetry across a range of water contents. A theory that …
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The tandem chain extension -aldol reaction of beta-keto esters
… of the TCEA reaction. A study, in which the steric bulk of the hydroxyacetaldehyde's protecting group was varied, has indicated that the erosion in syn-selectivity is likely due to complexation of the aldehydes hydroxy-functionality to zinc in the transition state of the TCEA …
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Modeling the active sites of non-heme diiron metalloproteins with sterically hindered carboxylates and syn N-Donor ligands
… the Fe-Fe distance occurs with the increase in steric bulk of the neutral donor L, resulting in values of up to 3 A without disassembly of the paddlewheel structure. Reactions with an excess of water do not lead to decomposition of the diiron(ll) core, indicating that these quadruply bridged …
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Modeling the active sites of diiron and dicopper metalloproteins with napthyridine-, phthalazine-, and diethynylbenzene-based ligands
… Hydroxide-Bridged Diiron(II) Complexes with a Sterically Hindered Phthalazine Ligand The synthesis and crystallographic characterization of a series of diiron(II) complexes with a sterically hindered bridging phthalazine ligand are presented. The compounds [Fe₂(Ph₄bdptz)([mu]-O₂CR)₂]²⁺ (R = CH₃ …
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Molecular design of conjugated polymers for the control of conformation, electronics and self-assembly
… complexes are attributed to the introduction of steric bulk that prevents the formation of quenched aggregates. The donor-acceptor strategy to bandgap engineering was applied to the preparation of a highly selective fluorescent probe for thiol bioimaging (Chapter 4), and to the synthesis of …
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Reductive coupling and related reactions with Mo and Ti tris- anilides
… unique combination of well-defined composition, steric bulk, and strong reducing ability embodied in Ti(N[t- Bu]Ar)₃ lends itself particularly well to mechanistic studies of the classical Pinacol coupling.
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