Search results for "Molecule"
showing 10 items of 5162 documents
ChemInform Abstract: LEAD TETRAACETATE OXIDATION OF PHENYLHYDRAZONES OF 3-BENZOYLAZOLES. SYNTHESIS OF AZOACETATES AND THEIR CONVERSION INTO INDAZOLES
1985
Lead tetraacetate (LTA) oxidation of (E)- and (Z)-phenylhydrazones of 3-benzoyl-5-phenyl-1,2,4-oxadiazole, 3-benzoyl-5-phenylisoxazole, and 3-benzoyl-4-methyl-1,2,5-oxadiazole has been studied. Conversion of azoacetate products into 3-(azol-3-yl)-substituted indazoles has been achieved by reacting them with aluminium chloride in benzene at room temperature.
Preparation of 4-substituted 1,3-oxathiolan-5-onesviathe sulphenium ion intermediate generated by the pummerer rearrangement
1993
4-Substituted 1,3-oxathiolan-5-ones have been synthesized via the Pummerer rearrangement from the S-oxide of the parent molecule. The 4,5-dione is obtained in the presence of pyridine N-oxide.
Studies towards the development of lipophilic bifunctional N3S3 chelators for 68Ga
2010
Abstract The present study is concerned with a concept of charge-neutral, lipophilic, macrocyclic bifunctional chelators, suitable for the introduction of a gallium-68 label into small molecules. The synthesis of a novel bifunctional N3S3-type chelator, derived from 1,4,7-triazacyclononane, initial 68Ga-radiolabelling and the determination of stability and calculated lipophilicity of the compound are described. The 68Ga-labelled chelate was obtained in a maximum radiochemical yield of 93±5% after a reaction time of 2 min. It remained intact over 3 h in a DTPA-challenge and a transferrin challenge experiment, indicating sufficient stability for PET studies.
Synthesis and properties of polymers with unusual structure
1985
This lecture summarize some recent results of our current research. The first part describes the homopolymerization and copolymerization of a monocyclic and two bicyclic unsaturated acetals. In this way polyacetals with 1,4-cis-butadiene units and cyclohexene units respectively are obtained. Secondly, the N-substitution of polyamides is described. By N-metalation and subsequent alkylation comb-like polyamides are available. Longer branches cause a side-chain crystallinity. The anionic “grafting-from” technique forms irregular branched polyamides. By termination reaction between living ends of poly(2-isopropenylnaphthalene) and suitable electrophiles new macromonomers are available. The last…
Quinonoid π-extended tetrathiafulvalenes (TTFs)
2001
Publisher Summary Tetrathiafulvalene (TTF) is a fascinating planar πelectron-donor molecule with a broad range of potential applications. TTF and its derivatives play an important role in the field of organic conductors forming charge-transfer (CT) complexes and radical cation salts (Bechgaard salts) with a huge variety of electron-acceptor molecules and anions in the search for electrically conducting and superconducting materials. The chapter focuses on highly π-extended electron donors with p-quinodimethane structures as interesting precursors of materials with non-conventional properties. The first dimeric examples of π-extended TTF derivatives connected through an oxygen atom are also …
Structural characterization in solution of multifunctional nucleotide coordination systems
2000
The interaction in aqueous solution of the cyclophane receptors 2,6,10,13,17,21-hexaaza[22]orthocyclophane (L11) and 2,6,10,13,17,21-hexaaza[22]paracyclophane (L22) with the nucleotides ATP, ADP and AMP has been studied by pH titration and NMR. The obtained results are compared with those previously reported for the analogous meta-substituted receptor 2,6,10,13,17,21-hexaaza[22]metacyclophane (L). All the experimental data support the actuation of these cyclophane molecules as multi-point binders of nucleotides through electrostatic, hydrogen bonding and π-stacking interactions. The combined use of NMR and molecular dynamics permits us to get a rather reliable picture of the way in which th…
QENS from polymeric micelles in supercritical CO[sub 2]
2000
We report QENS measurements from PS-b-PFOA aggregates in supercritical CO2. These consist of dense cores of CO2-insoluble polystyrene surrounded by a ‘corona’ of PFOA surfactant molecules whose CO2-philic groups interface with supercritical CO2. Lineshapes are dominated by localized diffusive modes and segmental dynamics of the anchored, finite-length PFOA chains. For Q∼0.6 A−1, we obtain effective diffusion coefficients of ≈0.8×10−6 cm2/sec. At higher Q, a single component is not sufficient as shown by excess intensity on the flanks. For Q>1.5 A−1, the wings reflect contributions due to a distribution of faster, more localized chain modes.
ChemInform Abstract: Synthesis, Structures and DFT Calculations on Alkaline-Earth Metal Azide-Crown Ether Complexes.
2008
The first examples of azide complexes of calcium, strontium or barium with crown ethers have been prepared and fully characterised, notably [Ba([18]crown-6)(N3)2(MeOH)], [Sr([15]crown-5)(N3)2(H2O)], [Ca([15]crown-5)(N3)2(H2O)] and [Sr([15]crown-5)(N3)(NO3)]. Crystal structures reveal the presence of a variety of coordination modes for the azide groups including 1-, -1,3- and linkages via H-bonded water molecules, in addition to azide ions. The [Ba([18]crown-6)(N3)2(MeOH)]1/3 MeOH contains dinuclear cations with three -1,3-NNN bridges, the first example of this type in main group chemistry. The structures obtained have been compared with molecular structures computed by density functional th…
- conformational preference of , -9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid
1985
Abstract The 1 H and 13 C nmr spectra of exo , exo -9-oxobicyclo[3.3.1]nonane-2,4-dicarboxylic acid, 3, in DMSO-d 6 or alkaline D 2 O, clearly show that it exists in a boat - chair -conformation with equatorial carboxyl groups, thus being the first case of boat - chair preference of a bicyclo[3.3.1] nonan-9-one due to the presence of exo , exo -2,4- substituents.