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  • General Chemistry  (329)
  • 2000-2004  (37)
  • 1960-1964  (292)
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  • 1
    Electronic Resource
    Electronic Resource
    Rhodium and Iridium β-Diiminate Complexes - Olefin Hydrogenation Step by Step (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 753-769 
    Details
    ISSN: 1434-1948
    Keywords: Hydrogenation ; Isomerization ; Rhodium ; Iridium ; Hydrides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The bulky β-diiminate ligands [(2,6-C6H3X2)NC(Me)CHC(Me)N(2,6-C6H3X2)]- (X = Me, LMe; X = Cl, LCl) have been found to be effective in stabilizing low coordination numbers (CN) in Rh and Ir complexes. The 14- complex LMeRh(COE) (COE = cyclooctene) has a three-coordinate T-shaped Rh environment and is nonagostic. Coordinative unsaturation is avoided by incorporation of a small ligand (e.g. N2, MeCN, olefins), by the intramolecular coordination of a chlorine atom in LClRh(COE), or by an agostic interaction in LMeRh(norbornene). In solution at room temperature, LMeRh(COE) undergoes rapid isomerization according to the allyl hydride mechanism; the corresponding 2,3-dimethylbutene complex actually prefers the allyl hydride structure. Rhodium(I) complexes of LMe and LCl catalyze olefin hydrogenation; hydrogenation of 2,3-dimethylbutene has been shown to be preceded by isomerization. The shielding properties of the bulky β-diiminate ligands allow direct observation of a number of reactive intermediates or their iridium analogues, including an olefin-dihydrogen complex (with Rh) and an olefin dihydride (with Ir). These observations, together with calculations on simple model systems, provide us with snapshots of a plausible hydrogenation cycle. Remarkably, hydrogenation according to this cycle appears to follow a 14-e/16-e path, in contrast to the more usual 16-e/18-e paths.
    Additional Material: 9 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    Synthese von Verbindungen, die in Beziehung zum Anhydrotetracyclin stehen (1964)
    Weinheim : Wiley-Blackwell
    Zeitschrift für die chemische Industrie 76 (1964), S. 791-791 
    Details
    ISSN: 0044-8249
    Keywords: Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/ange.19640761829
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  • 3
    Electronic Resource
    Electronic Resource
    Synthesis of α- and β-Substituted Aminoethane Sulfonamide Arginine-Glycine Mimics (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1219-1228 
    Details
    ISSN: 1434-193X
    Keywords: Peptidomimetics ; Peptidosulfonamides ; Peptidomimetics ; Transition-state isosteres ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -In this paper we present a synthesis of both α- and β-substituted aminoethane sulfonamide arginine mimics. The α-substituted sulfonamides were obtained starting from an alkene, whereas the β-substituted sulfonamides were derived from an amino acid derivative.
    Additional Material: 1 Ill.
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  • 4
    Electronic Resource
    Electronic Resource
    Study of Copper(II) Polyazamacrocyclic Complexes by Electronic Absorption Spectrophotometry and EPR Spectroscopy (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 559-565 
    Details
    ISSN: 1434-1948
    Keywords: Macrocyclic ligands ; Copper ; EPR spectroscopy ; Electronic spectrophotometry ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Copper(II) mononuclear complexes with the polyazamacrocyclic ligands NOTA (1,4,7-triazacyclononane-N,N′,N″triacetate), DOTA (1,4,7,10-tetraazacyclo-dodecane-N,N′,N″,N″′-tetraacetate), NOTP [1,4,7-triazacyclononane-N,N′,N″-tris(methylenephosphonate)] and DOTP [1,4,7,10tetraazacyclododecane-N,N′,N″,N‴-tetrakis(methylenephosphonate)] were characterised in aqueous solution by electronic absorption spectrophotometry and electron paramagnetic resonance (EPR) spectroscopy. While two isomeric species were detected by EPR spectroscopy in frozen samples of the polycarboxylate complexes, only one complex form was found for the poly(methylenephosphonate) systems. The results obtained are in accordance with a six-coordinate pattern for the metal centre, yielding tetragonally distorted complexes in solution, in agreement with previously reported studies on CuII complexes, both in solution and in the solid state.
    Additional Material: 3 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Ci Symmetric and Non-Centrosymmetric Crystalline Complexes of [60]Fullerene with Octakis(dimethylamino)porphyrazinato-Copper(II) and -Nickel(II) (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 593-596 
    Details
    ISSN: 1434-1948
    Keywords: Porphyrazines ; Fullerenes ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: X-ray structural analysis of octakis(dimethylamino)porphyrazinato-metallo(II)·[60]fullerene complexes (M = Cu2+ and Ni2+) surprisingly revealed two totally different supramolecular structures, the first exhibiting a Ci symmetric sandwich complex of two slightly dished porphyrazine units enclosing one fullerene sphere, the other featuring a noncentrosymmetric 1:1 complex with a strongly warped porphyrazine unit.
    Additional Material: 8 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Ionic Silver Amino Complexes Displaying Liquid Crystalline Behavior Close to Room Temperature (2000)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 2000 (2000), S. 133-138 
    Details
    ISSN: 1434-1948
    Keywords: Metallomesogens ; Liquid crystals ; Silver ; N ligands ; Amines ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The liquid crystalline properties of a series of ionic silver complexes [Ag(NH2n-CnH2n+1)2]X (X = NO3, n = 6, 8, 10, 12, 14; X = BF4, n = 8, 10, 12, 14), derived from silver nitrate or tetrafluoroborate and aliphatic amines, have been investigated by optical microscopy, DSC, and X-ray diffraction. The materials exhibit a birefringent fluid phase identified as a smectic A mesophase by optical microscopy and X-ray diffraction. Some of the complexes are liquid crystalline at temperatures close to room temperature. The X-ray results are consistent with the existence in the mesophase of a bilayer organization. The silver cations adopt a U-shape, which allows for the adoption of this bilayer arrangement, with alternating ionic and apolar regions and a short-range square-planar array inside the cationic sublayers. The thermodynamic parameters suggest that the melting transition clearly involves only disorder (melting) of the chains, whereas the clearing transition implies breaking the anion-cation arrangement.
    Additional Material: 6 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    Neutral Anion Receptors with Multiple Urea-Binding Sites (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 165-170 
    Details
    ISSN: 1434-193X
    Keywords: Neutral anion receptor ; Hydrogen bonds ; Urea moieties ; Donor-acceptor systems ; Macrocycles ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The synthesis of macrocyclic and acyclic cleft-like anion receptors in which four hydrogen bond donating urea moieties are present in a preorganized fashion is described. NMR spectroscopy shows the complex formation with H2PO4- and Cl -. Cleft-like receptors bind H2PO4- in a 2:1 guest-host stoichiometry (Ka = 107M-2) in DMSO, whereas Cl - is bound in a 1:1 stoichiometry (Ka = 103M-1). The macrocyclic receptors form a 1:1 complex with H2PO4- (Ka = 103M-1 in DMSO) with a 100-fold selectivity for H2PO4- over Cl -.
    Additional Material: 3 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Synthesis of (Hemi)Carceplex Adsorbates for Self-Assembly on Gold (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 269-274 
    Details
    ISSN: 1434-193X
    Keywords: Cage compounds ; Calixarenes ; Cavitands ; Carcerands ; Gold ; Interfaces ; Monolayers ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---The synthesis of sulfide-functionalized (hemi)carceplexes suitable for self-assembly on gold is described. A noncentrosymmetrical carceplex 9 (guest DMF) was synthesized by the combination of calix[4]arene 4 and resorcin[4]arene 3, while a noncentrosymmetrical hemicarceplex 12 (guest NMP) was prepared by the combination of two different resorcin[4]arenes, 3 and 10. These adsorbates form ordered self-assembled monolayers on gold with their quasi C4v axis perpendicular to the surface. The two positions possible for the incarcerated guest lead to diastereotopic surfaces.
    Additional Material: 1 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Synthesis of Allylic Isoprenoid Diphosphates by SN2 Displacement of Diethyl Phosphate (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 1401-1410 
    Details
    ISSN: 1434-193X
    Keywords: Phosphorylations ; Deuterium labeling ; Asymmetric labeling ; Terpenoid biosynthesis ; Enzyme inhibitors ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Allylic polyenyl diphosphates such as geranyl and (E,E,E)-geranylgeranyl diphosphates are ubiquitous substrates for monoterpene and diterpene synthases and transferases in isoprenoid biosynthesis. These enzyme substrates were prepared in asymmetrically labeled form by reduction of 1-deuterio aldehyde precursors with (R)- and (S)-Alpine boranes®, conversion into diethyl phosphates, and SN2 displacements with tris(tetrabutylammonium) pyrophosphate which occurred slowly with essentially complete inversion of configuration over 2-5 days. The 8α- and 8β-hydroxy-17-nor analogs (13 and 14) of copalyl diphosphate as well as the (15R)-deuterium-labeled form of 13 were similarly prepared from nor-diols 11, (15S)-[15-2H1]-11, and 12 by means of regioselective phosphorylation of the allylic hydroxy groups and displacements with pyrophosphate anion. The configurations and enantiopurities of the deuterium-labeled geraniols, before and after the SN2 displacements, and the diastereopurity of the bicyclic keto alcohol intermediate (15S)-[15-2H1]-15 were determined by conversion into (1S)-camphanate esters and 1H-NMR analysis. Amino alcohol 18 was similarly converted into amino diphosphate 19, 15-aza-14,15-dihydro GGPP, a potential aza analog inhibitor for diterpene synthases which generate stereoisomeric forms of copalyl diphosphate.
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  • 10
    Electronic Resource
    Electronic Resource
    Highly Substituted Homoallylvinylcyclopropanes by Indium-Mediated Reaction of α,β-Unsaturated Ketones and Aldehydes with Allylic Halides (2000)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 2000 (2000), S. 963-974 
    Details
    ISSN: 1434-193X
    Keywords: Indiumallyl compounds ; Vinylcyclopropanes ; α,β-Unsaturated carbonyl compounds ; Diastereoselectivity ; Dibenzylideneacetone ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---Allylindium reagents, prepared from excess allylic halide (Br or I) and indium metal, react with α,β-unsaturated ketones and aldehydes to give, after aerobic acidic workup, homoallyl-substituted vinylcyclopropanes. This process was explored and developed after a chance discovery arising from a side reaction in an attempted Pd-catalysed process. The structure of the cyclopropane arising from the reaction of bis(p-chlorobenzylidine)acetone was confirmed by X-ray crystallography. Whilst bis-α,β-unsaturated ketones give rise to a single homoallylcyclopropane species, α,β-unsaturated ketones and aldehydes give diastereomeric mixtures whose relative stereochemistry were assigned by NOE experiments. Crotylindium reagents react with good to perfect regioselectivity to afford tetrasubstituted cyclopropanes but prenylindium reagents fail to generate the analogous pentasubstituted rings.
    Additional Material: 5 Ill.
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