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  • 1985-1989  (1,688)
  • 1960-1964
  • 1830-1839
  • 1985  (1,688)
  • General Chemistry  (879)
  • Organic Chemistry  (671)
  • Atomic, Molecular and Optical Physics  (138)
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  • 1985-1989  (1,688)
  • 1960-1964
  • 1830-1839
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  • 101
    Electronic Resource
    Electronic Resource
    Quantitative Line-Shape Analysis of Temperature- and Concentration-Dependent 13C-NMR Spectra of 6Li- and 13C-Labelled Organolithium Compounds. Kinetic and Thermodynamic Data for Exchange Processes in Dibromomethyllithium, (Phenylthio)methyllithium, and Butyllithium (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1848-1862 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using the ‘permutation of indices’ method proposed by Kaplan and Fraenkel, we could formulate the density-matrix equations required to fit the temperature-dependent 13C-NMR spectra observed with the title compounds. For 6Li13CHBr2 (1) and 6Li13CH2SC6H5 (2) an exchange mechanism is proposed by which monomers interchange C- and Li-atoms via a non-observed dimeric intermediate; the activation parameters of these intermolecular dynamic processes have been found to be ΔH≠ = 10.2 kcal/mol, ΔS≠ = 13.7 cal/mol·K for 1 and ΔH≠ = 11.1 kcal/mol, ΔS≠ = 20.6 cal/mol·K for 2 ((D8)THF as solvent). In the case of (6Li)butyllithium (3), the observed low-temperature spectra indicate that dimeric (3b) and tetrameric (3a) species are in dynamic equilibrium interchanging the C3H713CH2 groups (and THF molecules) bonded to the 6Li-atoms. The relative concentrations of the dimer and of the tetramer have been determined by peak integration or by line-shape fitting; the ‘pseudo’- equilibrium constant, defined by K′eq = [3b]2/[3a], was found to be 2.6·10-2 mol/1 (at -88°) and corresponds to ΔGR (-88°) = 2 ΔG°f(3b) - ΔG°f(3a) = 1.34 kcal/mol. The activation parameters of the dynamic process responsible for the exchange were estimated as ΔH≠ = 3.78 kcal/mol and ΔS≠ = -31.3 cal/mol·K. Tentative interpretation of the thermodynamic and kinetic parameters is given.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680707
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  • 102
    Electronic Resource
    Electronic Resource
    Photochemical reactions. 146th communication145th Communication: [1].. Photochemistry of conjugated methano-epoxydienes: Participation of the neighboring cyclopropane ring in product formation via carbonyl ylide and carbene intermediates (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1583-1591 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On singlet excitation (λ = 254 nm, THF, pentane or hexane), the diastereoisomeric methano-epoxydienes (E)-6 and (E)-7 undergo interconversion and yield the products 8-11. The main process is the cleavage of the oxirane ring to the vinyl carbene intermediate e which undergoes addition to the adjacent double bond furnishing the cyclopropene 8. The alternative carbene intermediate f is evidenced by the formation of the cyclobutene 10. For the fragmentation leading to 11, the carbene f as well as the dipolar species h are considered as possible intermediates. On triplet sensitization (acetone, λ 〉 280 nm), (E)-7 shows behavior typical of epoxydienes, undergoing fission of the C—O bond of the oxirane ring and isomerization to the compounds 13, 14 and (E/Z)-15.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680610
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  • 103
    Electronic Resource
    Electronic Resource
    Metal Complexes with Macrocyclic Ligands. Part XXIPart XX: [1].. A nonlinear relationship between the stability of Cu2+ complexes and their complexation rate with 1,4,8,11-tetraazacyclotetradecaneDedicated to Prof. Dr. S. Fallab on the occasion of his 60th birthday (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1611-1616 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The kinetics of the reaction (1) between 1,4,8,11-tetraazacyclotetradecane (Cy) and a series of Cu(II) complexes CuL (L) = glycolate, malonate, succinate, picolinate, glycinate, iminodiacetate, nitrilotriacetate, N-(2-hydroxyethyl)ethylenediaminetriacetate, ethyienediamine, 1,3-diaminopropane, diethylenetriamine and N,N-bis(3-aminopropylamine) were studied spectrophotometrically at 25° and I = 0.5 (KNO3). From the analysis of the log kobs/log [L] profiles obtained at different pH values the resolved bimolecular rate constants kCyHnCuLm (Table 3) were obtained by a nonlinear curve-fitting procedure. For nearly all systems studied, the rate constant kCyHCuL, describing the reaction between the 1:1 complex CuL and the monoprotonated form of the macrocycle CyH, was obtained. The nonlinear relationship between log kCyHCuL and log KCuL and its nature is discussed. It is shown that the inverse relationship between reactivity and stability described by others is only a special case of the more general Eqn. 3 described here.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680613
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  • 104
    Electronic Resource
    Electronic Resource
    Reaktionskinetik einer Monomolekularen Oberflächenbelegung von Germanium mit 4-(Trichlorsilylmethyl)benzonitril mit Hilfe von FTIR-Experimenten (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1617-1623 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Kinetics of Monomolecular Surface Modification of 4-(Trichlorosilylmethyl)benzonitrile on Germanium by Means of FTIR ExperimentsA Fourier transform-attenuated total internal reflection-infrared spectroscopy (FT-ATR-IR) technique is described, which allows to observe the kinetics of monomolecular surface modification on materials which are feasible to total internal reflection experiments in an appropriate wavelength region. First results are reported for the reaction of 4-(trichlorosilymethyl)benzonitrile on germanium. The reaction is slower than expected and is only completed after approximately 4 h.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680614
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  • 105
    Electronic Resource
    Electronic Resource
    Über die Strukturaufklärung von (Hydroxy-oxo-cyclopentenyl)alkansäuren, den Aldolkondensationsprodukten von Dioxoencarbonsäuren aus RinderleberProf. Dr. Dr. h. c. H.-H. Inhoffen zum 80, Geburtstag gewidmet (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1624-1634 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Structure Elucidation of (Hydroxy-oxo-cyclopentenyl)alkanoic Acids, the Aldol-Condensation Products of Dioxoene Acids from Cattle LiverDuring homogenization of cattle liver the highly instable dioxoene acids 13a, 13b, and 13c are formed. These acids cyclize in alkaline solution to yield pairs of stable (hydroxy-oxo-cyclopentenyl)alkanoic acids, which were isolated as methyl esters 4a/5a, 4b/5b, and 4c/5c. The structures of these compounds were deduced from an enriched 3-mg mixture sample by microchemical reactions combined with a GC/MS analysis of the reaction products. Compound 13a was obtained as methyl ester by oxidation of the methyl ester of the corresponding F-acid with NaOCl. It was not possible to isolate 13a in pure form due to its high sensitivity. Instead of the methyl ester of 13a, 4a and 5a were isolated, of which the structures were established.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680615
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  • 106
    Electronic Resource
    Electronic Resource
    A Mild, Facile Method for the Preparation of Amino-esters (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1644-1646 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Lithium alcoholates prepared in situ react spontaneously with imidazolides derived from substituted aromatic carboxylic acids to provide the amino-esters 4 in excellent yield.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680618
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  • 107
    Electronic Resource
    Electronic Resource
    The Synthesis of 4,7-Bis(dialkylamino)tricyclo[5.2.1.04,10]deca-1(10),2,5,8-tetraenes and their Reduction with Alkali Metal (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1658-1669 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis and characterization of the novel 4,7-bis(dialkylamino)tricyclo[5.2.1.04,10]deca-1(10), 2,5,8-tetraenes 12 from 1,4,7-trihalotriquinacenes 8 and secondary amines is reported. The structural and electronic characteristics of these as well as the acepentalene dianion (32-) and some related systems as determined by semiempirical (MNDO) calculations are discussed. Thereby, 32- should be a triply etheno-bridged trimethylenemethane dianion exhibiting Y-delocalization favored over the formation of a peripheral 10π-electronic system. Attempts directed towards the generation of 32- by reacting tetraenes 12 with Na led to the formation of tris(dialkylamino)triquinacenes 9, presumably by a kind of reduction/disproportionation mechanism.
    Additional Material: 8 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680620
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  • 108
    Electronic Resource
    Electronic Resource
    Totalsynthese von Decarboxybetalainen durch photochemische Ringöffnung von 3-(4-Pyridyl)alaninTeilweise vorgetragen von M.A.S. An der Sitzung der Schweizerischen Chemischen Gesellschaft vom 3./4. Oktober 1975 in Aarau [1]. (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1670-1678 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Total Synthesis of Decarboxybetalaines by Photochemical Ring Opening of 3-(4-Pyridyl)alanineA photochemical approach is presented for the total synthesis of the decarboxybetalaines, which were previously known from the mild decarboxylation of the natural plant colorants, the betalaines: Irradiation of rac-3-(4-pyridyl)alanine (1) yielded the rac-2-decarboxybetalamic-acid-imine (4, 86%), presumably via a Dewar pyridine 2, a cyclic aminal 3 and an electrocyclic ring opening. The imine-zwitterion 4 was treated with three amines, namely (S)-cyclodopa (6), (S)-proline (7), and indoline (8), to afford three decarboxybetalaines, namely (2S)-17-decarboxybetanidine (9, red, 34%), (2S)-13-decarboxyindicaxanthine (10, yellow, 56%), and rac-16-decarboxyindobetalaine (11, orange, 78%), respectively. The structures of these coloring matters were confirmed by their electrophoretic behavior and their spectroscopic properties. 17-Decarboxybetanidine 9 was shown to be a ca. 1:1 mixture of two C(15)-epimers 9a and 9b, separable by chromatography. The configuration of 9a was determined as (2S, 15S) and that of 9b as (2S, 15R), by correlating their optical rotations with those of betanidine (12a) and isobetanidine (12b), respectively. The decarboxybetalaines 9, 10, and 11 did not show the double-bond isomerism at C(β), (Cγ) of the chromophore which had been found characteristic for the corresponding betalaines 12, 13, and 14.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680621
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  • 109
    Electronic Resource
    Electronic Resource
    Plantes de Nouvelle-Calédonie. 94e Communication93e communication: [1].. Alcaloïdes monoterpéniques de Scaevola racemigera DÄNIKER (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1679-1685 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Monoterpene Alkaloids of Scaevola racemigera DÄNIKERNine alkaloids have been isolated from the aerial parts of Scaevola racemigera. Two of them are the known compounds cantleyine (1) and tetrahydrocantleyine (2). The seven others are novel alkaloids, strychnovoline (3), 6-O-nicotinoylstrychnovoline (4), 6-O-nicotinoyltetrahydrocantleyine (5), 6-O-(5-vinylnicotinoyl)tetrahydrocantleyine (6), racemigerine (7), 6,7-epoxyracemigerine (8), and scaevoline (9). The structures of the new compounds have been elucidated by their spectral data and confirmed by chemical correlations. Moreover, the absolute configuration of 2, which had not been previously determined, has been elucidated.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680622
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  • 110
    Electronic Resource
    Electronic Resource
    Face Selectivity in the Diels-Alder Additions and Chelotropic Addition of Sulfur Dioxide to 2-(D)Methylidene-3-methylidenebicyclo[2.2.1]heptane (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1716-1729 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stereoselectivity of the cycloadditions of 2-(D)methylidene-3-methylidenebicyclo[2.2.1]heptane (4) to various dienophiles has been determined. The exo- vs. endo-face selectivity depends on the type of dienophiles, and for olefinic ones, on the mode of attack (Alder- vs. anti-Alder endo rule). It is 〉 9:1 with N-phenyltriazolinedione (NPTAD) and ethylenetetracarbonitrile (TCNE), 〈 1:9 with dimethyl acetylenedicarboxylate (DMAD), 30 ± 5:70 ± 5 with DMAD in the presence of AlCl3, 15 ± 5:85 ± 5 with dehydrobenzene and 40 ± 5:60 ± 5 with 1O2 generated photochemically (Table 1). With para-benzoquinone and maleic anhydride, the exo- vs. endo- face selectivity is 〈 1:9 and 20 ± 5:80 ± 5, respectively, for their anti-Alder mode of attack; it is 50 ± 5:50 ± 5 and 55 ± 5:45 ± 5, respectively, for their Alder mode of reaction. Under conditions of kinetic control, the chelotropic addition of SO2 to 4 is endo-face selective.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680628
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  • 111
    Electronic Resource
    Electronic Resource
    Nucleophilic Additions to N-Glycosylnitrones. Asymmetric Synthesis of α-Aminophosphonic AcidsParts of this work have been presented at the 5th International Conference on Organic Synthesis in Freiburg i. Br., 27-30/8/1984.Dedicated to Professor Dr. A. Eschenmoser on the occasion of his 60th birthday (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1730-1747 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hypothesis which explains the diastereoselectivity of the 1,3-dipolar cycloaddition of the N-glycosylnitrones 1-3 leading to the 5,5-disubstituted isoxazolidines 4-6 on the basis of a kinetic anomeric effect predicts that nucleophiles should add to N-glycosylnitrones with a high degree of diastereoselectivity. To test this prediction, the nucleophilic addition of lithium and potassium dialkylphosphites to the crystalline (Z)-nitrone 11, prepared from oxime 9 and (benzyloxy)acetaldehyde has been examined. The addition of lithium phosphites gave the N-glycosyl-N-hydroxyaminophosphonates 12-16 (d. e. 78-92%) in high yields (Scheme 4). The addition of potassium phosphites showed a much lower diastereoselectivity. Glycoside cleavage, hydrogenolysis, and dealkylation of 12-16 gave (+)-(S)-phosphoserine (+)-19 (34-45% from 9). Its absolute configuration was confirmed by an X-ray analysis of the N-(3,3,3-trifluoro-2-methoxy-2-phenylpropionyl) derivative 24. Similarly, the crystalline nitrone 25 gave the N-glycosyl-N-hydroxyaminophosphonate 26, which was transformed into (+)-(S)-phosphovaline (+)-31 (42% from 9). The diastereoselectivity of the nucleophilic addition and the enantiomeric purity of (+)-31 were determined by the analysis of the derivative 30 (d.e. 92%) and 32 (d.e. 93%), respectively. The addition of lithium diethyl phosphite to the nitrone 33, prepared in situ, gave the N-glycosyl-N-hydroxyaminophosphonate 34, (41%; d.e. 91%), which was transformed in (+)-(S)-phosphoalanine (+)-37 (21% from 9).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680629
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  • 112
    Electronic Resource
    Electronic Resource
    Structure and Reactivity of Xanthocorrinoids. Part IIPart I [1].. Influence of the c-acetic-acid chain on the course of the hydroxylation of the corrin chromophore by oxygen in the presence of ascorbic acidDedicated to Prof. Albert Eschenmoser on the occasion of his 60th birthday (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1754-1770 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The yield of the main product from the reaction of heptamethyl dicyanocobyrinate with O2 in the presence of ascorbic acid has been optimised by systematic variation of the reaction conditions, and the structure of the obtained ‘stable yellow corrinoid’ has been established by X-ray analysis. From the relationship between the structures of analogous xanthocorrinoids obtained likewise from a series of dicyanocobyrinic-acid derivatives, which has been prepared by systematic modifications of the c-acetic-acid chain, and the functionality of the substituent at C(7), a reaction mechanism is suggested.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680631
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  • 113
    Electronic Resource
    Electronic Resource
    Mitteilungen - Communications (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1815-1815 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680636
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  • 114
    Electronic Resource
    Electronic Resource
    Ringerweiterung bei der Reaktion eines 1,3-Cyclohexandions mit Diphenylcyclopropenon (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 2140-2147 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ring Expansion during the Reaction of a 1,3-Cyclohexanedione with DiphenylcyclopropenoneThe reaction of 5,5-dimethyl-1,3-cyclohexanedione (1) in form of its Na-salt with diphenylcyclopropenone (2) in DMF yielded the bicyclic triketone 3 (58 %), the structure of which was deduced as an enolizeable bicyclo[5.2.0]nonane-β-diketone from spectral data and from the following reactions: hydrolysis or methanolysis of 3 cleaved the β-dicarbonyl moiety, thereby opening the 4-membered ring to yield the keto acid 9 or its methyl ester 10. Methylation of 3 afforded the two enol ethers 4 and 5. The ether 5 readily underwent a thermal electrocyclic ring opening to the monocyclic enol ether 8, whereas the ether 4 was thermally stable. The same electrocylic ring opening (in boiling benzene) converted 3 (probably via 3b) to the monocyclic triketone 7, which was also the hydrolysis product of the ring-opened enol ether 8. By heating 3 in DMF/H2O, a partial (56 %) conversion to the lactone 6 took place. The tricyclic intermediate 11 was found useful to rationalize the ring expansion during the formation of 3 from 1 and 2 as well as the corresponding ring contraction during the conversion of 3 into 6.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680808
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  • 115
    Electronic Resource
    Electronic Resource
    Bestimmung des Chiralitätssinns der enantiomeren 2,6-Adamantandiole (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 1815-1821 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Determination of the Chirality Sense of the Enantiomeric 2,6-AdamantanediolsThe enantiomers of 2,6-adamantanediol (1) are resolved via the diastereoisomeric camphanoates. The (2R,6R)-chirality sense for (-)-1 and (2S,6S) for (+)-1 was determined by chemical correlation with (-)-(1R,5R)-bicyclo[3.3.1]nonan-2,6-dion ((1R,5R)-3) of known absolute configuration in the following way: alkylation of the bis(pyrrolidine enamine) of (-)-(1R,5R)-3 with CD2I2 and hydrolysis of the product gives the enantiomer 4 of (4,4-D2)-2,6-adamantanedione. Reduction of 4 with LiAlH4 leads to one enantiomer (Scheme 2) of each of the three diols 5-7 of known absolute configuration. The three diols are themselves configurational isomers due to the presence of the CD2 group, but correspond otherwise entirely to the enantiomeric diols 1. Accordingly, they can also be separated by means of their diastereoisomeric camphanoates to give the diols 5/6 and 7. These samples are easily distinguished and identified by their characteristic 1H-NMR spectra (cf. Fig. 2). This allows to identify the (2R,6R)- and (2S,6S)-enantiomer of 1 on the basis of their behavior in the resolution experiment analogous to that of the diols 5/6 and 7, respectively. The diol (-)-1 must have the (2R,6R)-configuration because it forms, like the diols 5/6, with (-)-camphanic acid the diastereoisomeric ester less soluble in benzene. The diol (+)-1 has (2S,6S)-configuration, because it forms, like 7, with (+)-camphanic acid the diastereoisomeric ester less soluble in benzene. The bis(4-methoxybenzoate) of (-)-(2R,6R)-1 shows chiroptical properties which are in accordance with Nakanishi's rule for two chromophores having coupled electric dipol transition moments arranged with a left-handed torsion angle.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680702
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  • 116
    Electronic Resource
    Electronic Resource
    Warped linear analytic tetrahedral scheme for brillouin zone integrations (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 97-101 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We provide an alternative to the biquadratic analytic scheme BIQ published earlier. This form, AMPLIN, is similar to the older linear analytic scheme, LIN. This scheme is much faster than BIQ.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560270108
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  • 117
    Electronic Resource
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    Announcement (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 105-105 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560270110
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  • 118
    Electronic Resource
    Electronic Resource
    Isoscalar factors for tetragonal, orthorhombic, monoclinic and triclinic shubnikov point groups (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 45-58 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The relations between isoscalar factors for corepresentations of antiunitary magnetic point groups are discussed in the case of associated corepresentations. The tables of the isoscalar factors for the single- and double-valued corepresentations of all tetragonal, orthorhombic, monoclinic, and triclinic Shubnikov point groups are given. Some peculiarities of the calculation method of the isoscalar factors for corepresentations are considered.
    Additional Material: 10 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560270104
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    Symmetrization of operator matrix elements (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 89-96 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The method of Dupuis and King for generating matrix elements of a totally symmetric one-electron operator in terms of symmetry-distinct integrals only is generalized to the case of nontotally symmetric operators. For operators constructed from two-electron integrals, explicit reduction of integral processing to permutationally inequivalent symmetry-distinct integrals only is described, while for one-electron operators further reductions are derived using double coset decompositions. Finally, some computational consequences of this approach are briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560270107
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    Masthead (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560270201
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  • 121
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    EOM/Propagator ionization potentials: Effect of an extended operator manifold on the predicted valence-shell ionization spectra of ethane, ethylene, and acetylene (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 145-157 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The orthogonalized direct diagonalization (ODD) method is used to predict the valence-shell ionization spectra for the series of hydrocarbons ethane (C2H6), ethylene (C2H4), and acetylene (C2H2) within an EOM/propagator formalism. Both (a) third-order and (b) higher-order (with h5 terms in the excitation operator manifold) calculations are presented in order to illustrate the effect of the extended operator manifold on the predicted valence-shell spectra. It is shown that the major effect of the h5 manifold is concentrated in its “occupied” part. Along with a general shifting of the main lines for outer valence ionizations to lower values (together with a slight reduction in pole strength), it is found that the effect of the h5 manifold in the inner valence region is dependent on the system being studied.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560270205
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  • 122
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    Anomeric effect in phosphate moieties of carbohydrates: An Ab initio study (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 181-194 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio SCF MO calculations at the STO-3G level have been carried out on CH2OHOPO3-H and CH2OHOPO32-, which have been considered as model systems for the Cl-phosphate moiety of sugars. The results predict higher anomeric energy for the phosphate moiety at Cl atom of pyranosides. Also a trans arrangement of the exocyclic O - P bond is preferred rather than a gauche arrangement, thus exhibiting a reverse exo-anomeric effect. A complete potential energy map has been constructed for CH3OPO3-H, a model system for C6-phosphate moiety. It is seen that the bond angle optimization brings down the relative energies of various conformations. The effect of the phosphate group on the preferred conformation of phosphate containing polysaccharides is also discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560270209
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  • 123
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    Calculation of internal rotation spectra of three molecules with increasing asymmetry factors (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 235-244 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Internal rotation energy levels for phenol, fluoracetaldehyde, and difluoracetaldehyde are estimated with two methods: first, by means of the reduced inertia moment formula introduced by Pitzer; second, with use of an internal axis system and by taking into account the influence of the overall rotation through the inertia factor. Two methods have been used to estimate potential barriers (CNDO/2 and PCILO). Results are related to the asymmetry of the tops. Theoretical far IR spectra for the three molecules are calculated. In the case of phenol, good agreement is found with experimental data.
    Additional Material: 7 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560270302
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  • 124
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    Ab initio studies of F-(H2O)n and Cl-(H2O)n clusters for n = 1, 2 (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 281-292 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Ab initio Hartree-Fock calculations are performed on hydrates of the F- and Cl- ions using 6-31G, 6-31G**, and 6-21G basis sets. Geometries and binding energies are obtained. An estimate of the correlation energy is provided by an MP2/6-31G (Møller-Plesset second-order perturbation) calculation. Comparisons are made between the Cl-(SO2) and the Cl-(H2O) complexes.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560270306
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  • 125
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    The hydrogen molecule for a two-dimensional system (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 375-379 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The two-dimensional (2D) energy of the hydrogen molecule is carried out by the Heitler-London method. The 2D integrals (which are more localized compared to 3D ones) are performed in the light of the 3D Slater integrals. A discussion of such 2D systems is briefly outlined for doped semiconductors.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560270402
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  • 126
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    Structure of the electronic energy bands of molecular crystal NMP-TCNQ (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 407-416 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electronic energy band of the molecular crystal NMP-TCNQ is calculated by means of the EHMO/LCAO-MO-CO method. In the calculation, both NMP and TCNQ are treated as quasi-one-dimensional columns, respectively. The results demonstrate that (i) the positions of the electronic energy bands of a molecular crystal are determined by that of the corresponding molecular orbitals of the respective isolated molecules; (ii) the widths of energy bands are determined by the interaction between the molecular orbitals of adjacent molecules in the crystal. These facts support the conclusion which we have given in the previous articles. The relationship between the structure of energy bands of the crystal NMP-TCNQ and its electrical conductivity at room temperature is discussed and compared with the crystal TTF-TCNQ. The differences of electrical conductivities of both crystals can be explained by the formula given by Fröhlich and Sewell.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/qua.560270405
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  • 127
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    Electronic structures of the π-π type charge-transfer complexes of pyridine with boron trihalides (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 465-473 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The electronic structures of the π-π type complexes of pyridine with boron trihalides have been studied by means of IEHMO calculation. The results indicate that BX3(X = F, Cl, Br, I) tends to react with C5H5N in a planar configurations against the plane of C5H5N. The most stable configurations of complexes are at 60° of orientation angle ϕ for X = Cl, Br, I, but at 0° for X = F. A linear relationship between In Eb, the logarithm of rotation potential barriers, and the radii of halogen atoms r0 has been observed, and has been deduced from Morse potential function. In the complex, the donating properties of BX3 have an increase from X = F to I, and BF3 functions as an acceptor, but the others as donors. It has been shown that every energy level of the complex is corresponding to that of the donor or the acceptor, which we have discussed by the perturbation theory. The bonds between D and A appear essentially as π-π type but not pure.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560270411
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  • 128
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    Compliant fields for molecular interactions: Water dimer and formic acid dimer (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 547-557 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The redundancy-free internal valence compliance constants of open-chain water dimer and formic acid cyclic dimer have been determined by the combined use of the CNDO/Force method and the compliance constant formalism. The final compliant fields of these dimers have been refined with the help of experimental frequency data.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560270504
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  • 129
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    New concepts in bonded functions theory. I. alternative way of matrix elements evaluation (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 613-623 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new method of evaluation of energy matrix elements has been derived for bonded functions of Boys and a spinless Hamiltonian. In configuration-driven CI algorithm the new approach is two to four times faster than the original Reeves' one, the relative speed depending on the case. In integral-driven CI the new approach is about 10 to 12 times faster than the equivalent approach based on the Reeves' scheme.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560270510
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  • 130
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    Many-Electron, multicenter integrals in superposition of correlated configurations method. I. one- and two-electron integrals (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 641-651 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The calculations by means of the superposition of correlated configurations method (Hylleraas-CI), that is, the combination of configuration interaction with the Hylleraas-type correlation factors, needs the effective evaluation of some nontrivial integrals. This series of papers gives the formulas for all types of integrals needed for molecular calculations when Gaussian lobe functions are used as a basis set. The formulas for two-electron integrals are given in the present paper. The preliminary results for two-electron systems are presented.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560270602
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  • 131
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    An extension of the pairing theorem (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 699-707 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: An extended pairing scheme is presented which ensures the fulfillment of pairing conditions not only between the sets of occupied orbitals for spin α and for spin β, but also between their orthogonal complements, i.e., the sets of virtual orbitals for spin α and spin β, as well as between occupied orbitals for spin α and virtual orbitals for spin β and between virtual orbitals for spin α and occupied orbitals for spin β. It is shown that the extended pairing properties are suggested by some aspects of the construction of alternant molecular orbitals. The algorithm for singular value decomposition of rectangular matrices is proposed for use in practical implementations of the (extended) pairing scheme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560270607
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    Limiting behavior of partition functions of models with quadratically dependent energy spectra and consequences regarding theoretical study of chemical reactivity (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 691-697 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conventional partition functions of models with quadratically dependent energy spectra (e.g., translation in a box or free internal rotation), which are widely used in literature, exhibit an incorrect limit behavior in the region of low temperatures and/or small values of the characterizing molecular parameter. In particular, this leads to the absurd value  - ∞ for the contribution of these motions to the entropy term at these limit conditions. This incorrect behavior appears to be due to the replacement of rigorous summation by integration in conventional derivation of these partition functions. The derived improved practical formulas with the correct limit behavior indicate that it will be necessary to carry out quite substantial numerical corrections in the case of many reactivity characteristics reported in the literature. Particularly, the improved formulas should be applied with (small) molecular complexes at the typical temperatures of their observation, e.g., van der Waals molecules with free internal rotation. Simultaneously discussed is the possibility of application of the functional relation valid for a rigorous partition function of the considered type of energy spectrum. The reasoning in the case of the translational partition function indicates that, in principle, it can depend on the vessel shape. Possible consequences for thermodynamics of the ideal gas are analyzed.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/qua.560270606
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  • 133
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    N-Representability conditions generated by a one-particle grassmann factor of an antisymmetric function (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 709-730 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N-representability conditions for a two-particle density operator implied by positive-semidefiniteness of the projection operator PN+1(φ1 Λ ΨN) are derived and discussed. The operator PN+1(φ1 Λ ΨN) projects onto an (N + 1)-particle antisymmetric function φ1 Λ ΨN, the Grassmann product of a one-particle factor φ1 and an N-particle factor ΨN. The polar subcone P2N(g, q) to the set of N-representable two-particle density operators P2N which corresponds to these conditions is found. It is shown that its extreme rays belong to two orbits for the action of the unitary group of transformations in one-particle Hilbert space. The facial structure of the convex set P2N exposed by elements of P2N(g, q) is analyzed. An example of the operator that changes the structure of its bottom eigenspace when the number of fermions N surpasses a certain value is noted. A new approach to the diagonal conditions for N-representability is found. It consists of the decomposition of the N-particle antisymmetric identity operator onto the mutually orthogonal projection operators.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560270608
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    Ab initio calculations on H transfer in the HF trimer (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 27 (1985), S. 781-786 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Systematic ab initio LCAO MO calculations with basis sets of increasing size have been performed to analyze the changes in relative stabilization energies of the two cyclic (D3h and C3h symmetry) and the noncyclic HF trimers. The results form the basis for a discussion of cyclic H-transfer reactions.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560270612
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    Chemical ordering of molecules: A graph theoretical approach to structure-property studies (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 1-16 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The problem of ordering of chemical structures and subsequent comparison of their relative properties is initiated here by an approach which uses chemical points of view as well as graph theoretical considerations. Briefly, a collection of structurally related compounds (such as isomers, but even more broadly, compounds of similar chemical architecture even if involving different atoms) is examined pairwise and the degree of structural similarity is deduced from a comparison matching of their skeletons. Depending on the nature of the similarity found, some compounds qualify as related and are depicted as vertices of a graph with the corresponding connection. The derived “comparison graph” represents the framework for subsequent comparison of selected molecular properties. “Comparison graph” can also be viewed as depicting a hierarchy of dominance for the compounds and can be drawn with arcs (directed edges), or alternatively as a poset (partially ordered set). Usefulness of such viewing on a collection of structures is illustrated on hexane and heptane isomers and their properties. The results are discussed, particularly with respect to alternative ordering schemes. It was found that the present approach complements and does not duplicate other results, thus offering some novel structural insights.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280102
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    Maximization of atomic information-entropy sum in configuration and momentum spaces (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 311-314 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The maximum entropy procedure (MEP) of Jaynes has been extended to the case involving constraints in complementary spaces. It has been rigorously shown that the sum of information entropies in position and momentum spaces is invariant to uniform scaling of the electron coordinates. A new MEP procedure requires that this sum of entropies must be maximized subject to the known constraints in both spaces. A specific application of this maximization procedure for synthesizing atomic-electron densities in coordinate and momentum spaces has been outlined.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280212
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    Molecular orbital study of the ring nitrogen basicity of various dihydrofolate reductase inhibitors (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 315-334 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We present molecular orbital (CNDO/2) calculations on the key fragments of different dihydrofolate reductase inhibitors. Distance geometry analysis, physicochemical parameter dependent QSAR, and molecular shape analysis raised some questions regarding the basicity of the ring nitrogen (N1) in these inhibitors and the effect of the various substituents on the basicity. We show that the ring nitrogen N1 of methotrexate has a considerably higher tendency to be protonated compared to that of folic acid. However, not all 2,4-diamino inhibitors are equally basic. Even 2-amino-4-hydroxyquinazoline is sufficiently basic to be protonated, but not the 2,4-diamino-5-sulfonyl derivatives. The pyrimidinium ion seems to be highly solvated, since in spite of its high protonation energy it is strongly basic. Triazines were found to be the most basic of all the classes studied.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280302
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    Bond order and valence: Relations to Mulliken's population analysis (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 419-419 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280309
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  • 139
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    Theoretical studies on the interaction of proteins with base pairs. II. Effect of external H-bond interactions on the stability of guanine-cytosine and non-Watson-Crick pairs (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 399-409 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We studied the stability of guanine-cytosine and non-Watson-Crick pairs in the presence of H-bond interactions with various amino acid side chains, by using ab initio MO method. The external H-bond interactions stabilize or destabilize the base pairs, depending on the type of interacting residues and the site of the interaction. The pattern of the H-bond effect on the base-pair stability is quite different than in the case of adenine-uracil pair previously reported. From the present results, together with the previous results on adenine-uracil pair, we obtain a general rule for the effect of external H-bond interactions on the stability of base pairs. The site-specific effect of the H-bond interactions can be consistently explained by the cooperative interaction between external and base-pair H bonds. We discuss the application of the present results in the following biological processes: One is the protein-induced specific melting of double-stranded DNA, which is involved in transcription process. The present results suggest that H-bond interactions of protein residues at specific site of base pairs can weaken base-pair H bonding, which would assist the opening of double-stranded DNA. The other is the control of mutation in replication process. We suggest that proteins can discriminate non-Watson-Crick pairs against Watson-Crick pairs by H-bond interactions and can either induce or suppress mutation during DNA replication.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280307
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  • 140
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    Bond length alternation in cyclic polyenes. VI. Coupled cluster approach with wannier orbital basis (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 459-479 
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    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The role of electron correlation effects on the bond-length alternation in linear metalliclike systems, as modeled by cyclic polyenes CNHN, N = 2n = 4v + 2, v = 1,2,…, is examined using the coupled cluster approach in the localized Wannier basis formalism. A recently developed approximate coupled pair approach which accounts for connected quadruply excited clusters is employed together with various truncation schemes for the localized doubly-excited cluster components. It is found that for the physical value of the coupling constant, the electron correlation has only a very slight effect on the potential energy curves, yielding almost the same values for both the magnitude of the bond-length alternation and for the stabilization energy relative to the symmetric equidistant structures as the restricted Hartree-Fock theory. This is in contrast to a strongly correlated region where the correlation effects stabilize the undistorted non-alternating structures. Different mechanisms of the bond-length alternation or Peierl's distortion as implied by a simple Hückel Hamiltonian and by the Pariser-Parr-Pople Hamiltonian models are also pointed out.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280405
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    Masthead (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280501
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    The INDO/2-AHP (average hole potential) method for excited states: Comparison with the simple INDO/2-HP (hole potential) method (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 565-571 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The INDO/2 version of the average hole potential (AHP) model is analyzed. The model is applied to study the geometric features, molecular inversion barriers, singlet-triplet splittings, etc., of a few small carbonyl molecules (H2CO, HFCO, F2CO) in the 1,3nπ* states with partial as well as complete optimization of all geometric parameters in the excited states. The results are compared with those obtained by a simple hole-potential (HP) model.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280503
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  • 143
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    Perturbation calculation on the hydrogen atom in electric and magnetic fields (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 603-607 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A generalization of a perturbation theory without wave function is developed which applies to a hydrogen atom perturbed by magnetic and electric fields. A double perturbation expansion for the Stark-Zeeman effect for parallel fields is considered and results for the states obeying |m| = l = n - 1 in the zero field limit are presented. Other problems that can be treated this way are discussed.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280507
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  • 144
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    Effect of some factors on the energy band structure of proteins (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 573-579 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effects of four factors (different side chains, side-chain disorder, conformational change, and ions and water) on the energy band structures of proteins have been investigated with the aid of the CNDO/2 crystal orbital method. The results indicate that these factors are very important. The consequences of these effects on the semiconductive properties of proteins are discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280504
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  • 145
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    Masthead (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985) 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280601
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  • 146
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    A quality test for the Hartree-Fock-Roothaan SCF wave functions (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 687-690 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A quality test for the SCF wave function based on separate examination of the one- and two-electron contributions to the total energy is proposed. The test is applied to 12 different STO basis sets for the ground state of the Ni atom and its predictions compared with those deduced for the minimization of the total energy. The new test allows for a reduction in the cancellation of errors detected in some applications of the standard SCF procedure. Some relations between the quality of the basis set and its size and structure are discussed.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280603
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  • 147
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    On the evaluation of the integral 〈pu|∂/∂ν|s〉 occurring in covalency reduction factor (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 723-729 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Explicit expressions for integrals of the form 〈pu|∂/∂ν|s〉 occurring in expression of covalence reduction factors, introduced by Stevens and Tinkham, have been derived for various types of atomic functions. Numerical values of the integral for some common ligands are given. Misconceptions regarding the sign and the magnitude of this integral existing in the literature have been clarified.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280607
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  • 148
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    Cation-ligand interactions: Reproduction of extended basis set Ab initio SCF computations by the SIBFA 2 additive procedure (1985)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 28 (1985), S. 757-771 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In the framework of the additive SIBFA 2 procedure, the intermolecular interaction energy is computed as a sum of five terms: ΔE = EMTP + Erep + Epol + ECT + Edisp. In order to assess the accuracy of the procedure to compute cation-ligand interactions, the interaction of alkali (Na+, K+) and alkaline-earth (Mg2+, Ca2+) cations with two representative ligands H2O and HCOO- has been studied and the results compared with those of ab initio SCF extended basis set computations. The additive procedure reproduces very satisfactorily the results of ab initio computations as concerns the numerical values of the interaction energies and the equilibrium cation-ligand distances, as well as the evolution of the energy components. A detailed study of these components at different distances helps, in particular, to delineate the relative weights of the charge-transfer and polarization contributions within the second-order energy.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560280610
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  • 149
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    Melanotropin Receptors II. Synthesis and Biological Activity of α-Melanotropin/Tobacco Mosaic Virus Disulfide ConjugatesParts of this report have appeared as a thesis [1]. P.M. was on leave from the Chemistry Dept., Univ. of Athens; S.D.S. from the Central Drug Research Institute, Lucknow. Nomenclature and abbreviations, see [2] and Experimental. TMV is tobacco mosaic virus wild type.Dedicated to Prof. Dr. Hans Neurath on the occasion of his 75th birthday (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 12-22 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Asymmetric disulfide conjugates of mercaptosuccinyl tobacco mosaic virus (TMV ∼ SH) with Nα-desacetyl-Nα-5-(mercaptovaleryl)-α-melanotropin were prepared via the S-sulfoderivative of the peptide. The conjugates, TMV ∼ S—S ∼ α-MSH(n), contained up to n = 330 disulfide-linked peptide molecules/virion. Similarly, fluorescent conjugates, Rh(m) ∼ TMV ∼ S—S ∼ α-MSH(n) were prepared, containing m ≍ 200 rhodamine molecules linked to the virions by thiourea bridges. Such conjugates were designed to study α-MSH receptor localization and dynamics (mainly internalization), because the carrier virions which served to enhance specific receptor binding and as fluorescent or radioactive markers may be detached from the neuropeptides at will by reduction. Reduction occurred in solution and on the cell surface, but not in the cytoplasm, thus allowing detection of internalized agonist-receptor complexes. The conjugates were superpotent agonists for tyrosinase stimulation in Cloudman S-91 melanoma cell cultures, but were inactive for cyclic AMP accumulation. Their rather rapid internalization and the influence of reducing agents and other agonists on their biologic activity suggest a close connection between receptor location and biologic response as well as the presence of essential receptor HS-groups.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680103
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  • 150
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    Halochrome Molekeln. 5. Mitteilung. Synthese substituierter 6H-Chromeno[4,3-b]indolizine und ihrer Aza-analogen (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 56-63 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Halochromic Molecules. Synthesis of Substituted 6H-Chromeno[4,3-b]indolizines and their Aza-analoguesWe have synthesized a series of substituted chromeno[4,3-b]indolizines and their respective aza-analogues. Dyes generated from them contain the electrondonating 2-(2-hydroxy-5-methylphenyl)indolizin-3-yl moiety. The 90 MHz FT 1H-NMR spectra of starting and final products supported the postulated structures. Fragmentations in the mass spectra also were consistent with the assumed structures.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680107
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  • 151
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    Probes for a Regulatory Site on the Nicotinic Acetylcholine Receptor-Channel. Synthesis of (±)-7-Debutylperhydrohistrionicotoxin, (±)-2-Depentyl-7-debutylperhydrohistrionicotoxin, and their Analogues (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 49-55 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of glutarimide with pent-4-enylmagnesium bromide, followed by cyclization of intermediate ketoamide, and hydrolysis of the formates 10 and 13 led to the mixture of the hydroxylactams 11 (cis) and 14 (trans) which could be separated via their benzenecarbamates. Reduction of cis-hydroxylactam 11 with LiAlH4 yielded 2-depentyl-7-debutylperhydrohistrionicotoxin (6), whereas reduction of trans-isomer 14 gave the epimeric alcohol 9. cis-Hydroxylactam 11 was converted via thiolactam 17 and the methylthio derivative 18 to ketimine 19 which was reduced with NaBH4 yielding a mixture of natural 4 and unnatural 7, analogues of perhydrohistrionicotoxin (2). Reduction of 4 with H2 in the presence of Pd/C yielded (±)-7-debutylperhydrohistrionicotoxin (5).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680106
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  • 152
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    β-Funktionalisierte Hydrazine aus N-Phthalimidoaziridinen und ihre hydrogenolytische N,N-Spaltung zu Aminen (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 220-230 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: β-Functionalized Hydrazines from N-Phthalimidoaziridines and their Hydrogenolytic N,N-Cleavage to AminesThe three N-phthalimido-aziridines 1-3 were reacted with phenol, thiophenol, aniline, p-toluenesulfonic acid, and H2O in selected combinations. These nucleophiles opened the 3-membered ring to yield the N-phthalimidoamines 4a-d, 5a-d, 6a-c, and 6e; all these products (except the carbinol 6e) carry an aryl-substituted functional group on the C-atom vicinal to the N-substituent. Hydrazinolysis of 4, 5, 6a-c, and 6e afforded the β-functionalized hydrazines 7, 8, 9a-c, and 9e. The reducing medium Raney-Ni/N2H4 transformed 4, 5, 6a-c, and 6e to the β-functionalized amines 10, 11, 12a-c, and 12e. By a study with the hydrazide 6a and the hydrazine 9a, it was shown that the N,N-cleavage is a catalytic hydrogenolysis by H2 generated from N2H4 with Raney-Ni and that it does not take place on the hydrazide 6, but rather on the hydrazine 9, generated as intermediate from 6 with N2H4. Spectroscopic data confirmed that the conversions of 1-3 to 4-6 occurred exclusively with inversion and that the resulting configurations remained fully intact during the transformations of 4, 5, and 6 (via 7, 8, and 9) to 10, 11, and 12, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680128
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  • 153
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    Synthèse électrochimique de complexes Ni(O)-diazabutadiène (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 248-254 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Electrochemical Synthesis of the Ni(O)-Diazabutadiene ComplexesThe electrochemical reduction of Ni salts in the presence of diazabutadiene ligands (DAB = R—N=CH—CH=N—R, R = t-Bu, o-xylyl, p-anisoyl, p-tolyl) has been studied in DMF by cyclic voltammetry and rotating disc polarography. In solutions containing DAB and halide X-, Ni(II) can be reduced to Ni(DAB)2, and the features of this reduction agree with a mechanism where the second DAB replaces X- in the coordination sphere of Ni only after its reduction to Ni(O). Rather concentrated (≃ 0.1M) solutions of NiBr2 · DME and DAB in DMF have been electrolyzed without a supporting electrolyte, making the isolation of the product Ni(DAB)2 particularly easy. Thus, gram quantities of Ni(DAB)2 can be conveniently prepared within a few hours.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680131
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  • 154
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    Masthead (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680201
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  • 155
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    Synthesis of Macrobicyclic Polyamines by Direct Macrobicyclisation via Tripode-Tripode Coupling (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 289-299 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of five macrobicyclic polyamines 1-5 is described following a route in which the macrobicycle is formed by the coupling of two tripodal subunits. Such a sequence is appreciably shorter than the stepwise construction via a macrocycle, and may give higher yields, as illustrated by the case of bis-tren 3, which has been synthesized following both routes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680202
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  • 156
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    Tritylketone und Tritylenone. Beiträge zur sterisch erzwungenen Michael-Addition und zur diastereoselektiven Aldol-AdditionTeilweise in vorläufigen Mitteilungen publiziert [1].Herrn Prof. Dr. Günther Wilke zum 60. Geburtstage gewidmet (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 264-282 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Tritylketones and Tritylenones. Contributions to the Sterically Enforced Michael Addition and to the Diastereoselective Aldol AdditionTritylketones are prepared from trityllithium and aldehydes, with subsequent CrO3 oxidation (Scheme 1, 2a-f). Tritylenones are obtained from the saturated ketones and aldehydes or ketones, preferably by (CH3)3Al-mediated aldol addition with subsequent dehydration (Scheme 2, products 2e, 4b-e). The carbonyl of the tritylketone group is sterically protected, but electronically effective (see A-C); thus, amine-free enolate solutions can be obtained directly with BuLi; also, exclusive conjugate addition of organolithium derivatives occurs with tritylenones (Schemes 3-5, products 2d, 5-7, 15 examples). The lithiumenolates of tritylketones add to aldehydes with practically complete stereoselectivity (Scheme 6, products 10, 9 examples): due to the bulkiness of the trityl group, only the (Z)-enolates 8 are formed, and the approach of the two trigonal centers in the aldol-addition step is enforced to occur with relative topicity ul. As a first example of an X-ray structure determination of a silyl enol ether, the crystal structure of (Z)-2-(trimethylsilyloxy)-1, 1, 1-triphenyl-2-butene (9) is reported. Fortunately, the blocking of the carbonyl group in trityl ketones can be run very specifically (without epimerization at the α-carbonyl center) by lithium triethylborohydride to furnish, after aqueous workup, primary alcohols and Ph3CH (Eqn. 4, products 13-20, 10 examples); the OH-group of the aldols 10 must be EE-, MOM- or MEM-protected (Scheme 8) before this C,C-bond cleavage can be conveyed. Some of the cleavage products are used for the chemical correlation of the aldol configuration and for the demonstration of the synthetic value of the presented method (see 21-29).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680133
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  • 157
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    Disproof of the Overall Enzymatic Biosynthesis of Vindoline from Tryptamine and Secologanin by Cell-Free Extracts from the Leaves of Catharanthus roseus (L.) G. DON (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 315-318 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A cell-free extract, which was isolated from the leaves of mature Catharanthus roseus plants by a previously published procedure, does not convert a mixture of secologanin and radiolabelled tryptamine to vindoline, as was recently claimed. The radioactivity in the purified alkaloid extract determined by earlier workers is certainly due to ‘impurities’ in the presumed ‘vindoline’. This was shown by extensive purification of the alkaloid extract (which contained added unlabelled vindoline as a carrier) followed by chemical conversion of vindoline to two derivatives and subsequent purification, ultimately giving unlabelled deacetylvindoline.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680204
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  • 158
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    Reduktion von 1,2-bis[(Z)-(2-nitrophenyl)-NNO-azoxy]benzolBei der Benennung von 2 war in [1] irrtümlich der Deskriptor ONN anstelle von NNO verwendet worden; 2 kann auch als 2,2′-Dinitro-1,1′-[(Z,Z)-1,2-phenylenbis(ONN-azoxy)]dibenzol benannt werden.: Synthese von Cyclotrisazobenzol ( = (5E,6aZ,11E,12aZ,17E,18aZ)-5,6,11,12,17,18-Hexaazatribenzo[aei][1,3,5,7,9,11]cyclododeca-hexaen) (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 325-333 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reduction of 1,2-Bis[(Z)-(2-nitrophenyl)-NNO-azoxy]benzene1: Synthesis of Cyclotrisazobenzene ( = (5E,6aZ,11E,12aZ,17E,18aZ)-5,6,11,12,17,18-Hexaazatribenzo[aei][1,3,5,7,9,11]cyclododeca-hexaene)Na2S reduction of 1,2-bis[(Z)-(2-nitrophenyl)-NNO-azoxy]benzene (2) yielded 3 deoxygenated products: the (known) red 2,2′-((E,E)-1,2-phenylenbisazo)dianiline (3, 23%), the orange 2-[2-((E)-2-aminophenylazo)phenyl]-2H-benzotriazol (4, 55%) and the colorless 2,2′-(1,2-phenylene)di-2H-benzotriazol (5, 13%). The constitutions of 3-5 and of 6, the N-acetyl derivative of 4, were deduced from their 1H-NMR spectra (chemical shifts, couplings, and symmetry properties), and the configurations of 3, 4, and 6 at their N,N-double bonds are assumed to be the same as in 2. Oxidation of 3 with 2 mol-equiv. of Pb(OAc)4 afforded 5 (47%) and a novel, highly symmetrical macrocycle, called cyclotrisazobenzene (7, 24%). The constitution of 7 as a tribenzo-hexaaza[12]annulene and its (E)-configuration at the N,N-bonds was confirmed by X-ray analysis. The molecular symmetry expressed by the 1H-, 13C- and 15N-NMR spectra of 7 reveals a rapid torsional motion around the six N,C bonds. This implies that the N,N-double bonds in the cyclic 12π-electron system (or 24π-electron system if the benzene rings are included) of 7 are highly localized.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19850680206
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  • 159
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    The Radical Anions of syn-1,6:8,13-Bridged [14] Annulenes. A Compilation of Hyperfine Data (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 371-376 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hyperfine coupling constants and g-factors determined by ESR and ENDOR spectroscopy are given for the radical anions of 21 syn-1,6:8,13-bridged [14]annulenes. The great majority of these values is reported for the first time. The hyperfine data are consistent with the single occupancy of an orbital which resembles a π-perimeter-LUMO of the same nodal properties. The sum of the coupling constants of the protons attached to the π-perimeter can be used as a planarity criterion for this perimeter.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19850680211
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  • 160
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    Umlagerungsreaktionen von (2′-Propinyl)cyclohexadienolen und -semibenzolenIm folgenden werden nach einem Vorschlag von v. Auwers [1] die Bezeichnungen o- und p-Semibenzol für 6-Alkyliden-1,3-cyclohexadiene bzw. 6-Alkyliden-1,4-cyclohexadiene verwendet. (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 355-370 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Rearrangements of (2′-Propinyl)cyclohexadienols and -semibenzenesThe acid-catalyzed dienol-benzene rearrangement of 3- and 5-methyl-substituted (2′-propinyl)cyclohexadienols has been investigated. Treatment of the dienols with CF3COOH in CCl4 yields allenyl- and (2′-propinyl)benzenes via [3,4]- and [1,2]-sigmatropic rearrangements, respectively. The reaction with H2SO4 in Et2O leeds to a mixture of allenyl-, 2′-propinyl-, 3′-butinyl- and (2′,3′-butadienyl)benzenes (Scheme 3). The latter are products of a thermal semibenzene-benzene rearrangement (cf. Scheme 9). The corresponding semibenzenes have been prepared by dehydration of the cyclohexadienols with H2SO4 or POCl3 (Schemes 6 and 7). Under acidic conditions, the p-(2′-propinyl)semibenzenes 33-35 (Scheme 8) undergo [3,4]- and [1,2]-sigmatropic rearrangements to give again allenyl- and (2′-propinyl)benzenes, whereas the thermal rearrangements to the 3′-butinyl- and (2′,3′-butadienyl)benzenes (Scheme 9) involves a radical mechanism. In contrast, the o-(2′-propinyl)semibenzene b (Scheme 7) leads to (2′,3′-butadienyl)benzene 32 via a thermal [3,3]-sigmatropic rearrangement.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680210
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    Skeletal Migrations Observed during the Cob(I)alamin-Catalyzed Reduction of 4β-(tert-Butyl)-1β-(1-methylvinyl)cyclohexanecarbaldehyde15th Communication in the series ‘Cob(I)alamin as Catalyst’; for the 14th communication, see [1a]; for the structural formulae of cob(I)- and cob(III)alamin(1(I), 1(III)), cf. Scheme 1 in [1b].Dedicated to Professor Dr. K. Bernauer on the occasion of his 60th birthday (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 181-184 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: During the cob(I)alamin(1(I))-catalyzed reduction of 3, intermediate formation of 2 and final generation of 4-10 was observed (see Scheme 1, cf. Tables 1 and 2). Identical products in similar ratios were generated starting from either 2 or 3. Accepting the intermediate formation of six interconnected cobalt complexes, i.e. A-F (cf. Scheme 2), the generation of all the products observed can be explained.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19850680122
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  • 162
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    Asymmetric α-Acetoxylation of Carboxylic Esters. Preliminary CommunicationPresented by W. O. as part of a Simonsen-Lecture, London, November 27, 1984. (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 216-219 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Using the readily accessible chiral auxiliaries 1-3 the sulfonamide-shielded O-silylated esters 5 underwent π-face-selective α-acetoxylation on successive treatment with Pb(OAc)4 and NEt3 HF to give after recrystallization α-acetoxy ester 6 in 55-67% yields and in 95-100% d.e. Starting from conjugated enoates addition of RCu and subsequent acetoxylation 10→11→12 yielded α,β-bifunctionalized esters 12 with 〉95% configurational control at both Cα and Cβ. Nondestructive removal of the auxiliary (6→7, 6→8 and 12→13) gave either α-hydroxycarboxylic acids or terminal α-glycols in high enantiomeric purity. The prepared glycols 8c and 13a are key intermediates for previously reported syntheses of the natural products 16 and 17, respectively.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19850680127
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  • 163
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    Synthese und Reaktionen von Bicyclo[6.4.0]dodecan-3-carbonsäure-DerivatenHerrn Prof. Dr. Karl Schlögl mit den besten Wünschen zum 60. Geburtstag gewidmet (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 231-235 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis and Reactions of the Bicyclo[6.4.0]dodecane-3-carboxylic Acid DerivativesThe synthesis and some consecutive reactions of the compounds 5-8, derivatives of bicyclo[6.4.0]dodecane-3-carboxylic acid (1), are described. The esters 7 and 8 can be obtained by Baeyer-Villiger oxidation of 2-hydroxy-8-methyltricyclo[7.3.1.02,7]tridecan-13-one (4) and subsequent hydrolysis of the lactone 5. The structure and configuration of these compounds has been evaluated by spectroscopic techniques (mainly 2D-NMR methods). The formation of 7 via 1,2-H shift and subsequent isomerization to 8 has been studied. The esters 11 and 13 are formed stereospecifically from 7 and 8.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680129
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  • 164
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    d6 and d8 Metal Carbonyl Complexes of 7,7-Dimethoxy-5,6-dimethylidenebicyclo[2.2.1]hept-2-ene. Stereoselective Hydroformylation of an [Fe(CO)4(olefin)] Complex (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 236-247 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of 7,7-dimethoxy-5,6-dimethylidenebicyclo[2.2.1]hept-2-ene (2) with various metal carbonyls and their derivatives gave the η2-M(CO)4 (M = Fe (17), Ru (18)), η4-M(CO)3 (M = Fe (19x, 19n), Ru (20n)), and η2-M(CO)5 and η6-M(CO)3 (M = Cr, Mo, W) complexes. The trigonal bipyramidal η2-M(CO)4 complexes present an exceptional C3v symmetry at the metal with the C,C-double bond in an axial position. In all the η2-complexes, this double bond is stereospecifically coordinated by its exo-vs. endo-η4-Fe(CO)3 configuration was established by chemical correlation (hydrolysis, hydrogenation) with the corresponding complexes (24x, 24n) of 7,7-dimethoxy-2,3-dimethylidenebicyclo[2.2.1]heptane (5). The relative rates of hydrolysis (AcOH/H2O 2:1, 50°C) of ligands 2 and 5 and of complexes 19x, 19n, 24x, and 24n to the corresponding ketones showed an acceleration effect only when the metal is coordinated to the exo-face. This was attributed to an F-strain effect on the leaving group of the substrate. Compound 17 was further metallated by [Fe2(CO)9] giving the bimetallic isomers 21xn and 21xx. The endocyclic C,C-double bond of the latter can be stereospecifically hydroformylated (1 atm CO, AcOH/H2O, 25°C) giving 29x (49%). Hydroformylation of 17 gave the corresponding uncoordinated aldehydes 30x/30n in better yields (76%) but with lower selectivity (3:1). These are the first examples of hydroformylation of an isolated [Fe(CO)4(olefin)] complex.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19850680130
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  • 165
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    Synthesen von stellungsisomeren Alkoxyformylderivaten des 1,6-Methano[10]annulensHerrn Prof. Dr. Dr. h.e.mult. Günther Wilke in grosser Dankbarkeit zum 60. Geburtstag gewidmet (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 255-263 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses of Positionisomeric Alkoxyformylderivatives of 1,6-Methano[10]annulenesDifferent aldehydes of 1,6-methano[10]annulene - namely 3-6, 11, 12, 15, and 19 - were synthesized. They can be used as starting materials for synthetic reactions of other new bridged systems; the results of 1H-NMR- and 13C-NMR measurements are included.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19850680132
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  • 166
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    Stereoselective glycosylation of Alcohols and Silyl Ethers Using Glycosyl Fluorides and Boron Trifluoride Etherate (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 283-287 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The stereoselective glycosylation of alcohols and their silyl ethers has been achieved using O-alkyl-, O-acyl-, and acetal-protected glycosyl fluorides of the pyranose and furanose series and boron trifluoride etherate in CH2Cl2.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19850680134
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  • 167
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    Mitteilungen - Communications (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 288-292 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680135
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  • 168
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    On Cardioactive Steroids. XVI. Stereoselective β-Glycosylation of Digitoxose: The Synthesis of DigitoxinFor communication No. XV, see [1]. Systematic names of all compounds are given in the Exper. Part. (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 300-314 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two methods for stereoselective β-glycosylation of digitoxose were developed. The first achieved stereocontrol by a 1,3-participation of a N-methylurethane group under acid catalysis. The second utilized mercuric-ion catalyzed cleavage of thioglycosides and a 1,3-participation of a p-methoxybenzoyl group in a neutral medium. The first highly stereoselective and quite efficient synthesis of digitoxin (C7) was achieved by a combination of these methods. The furyl-substituted precursor IV of digitoxigenin (Scheme 1) was used as aglycone, and the furan group was converted to the unsaturated lactone of digitoxin by our known oxidation procedure (m-chloroperbenzoic acid/NaBH4) after the assembly of the carbohydrate portion of the molecule and its deblocking was completed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680203
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  • 169
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    Reversed Stereochemical Course of the Michael Addition of Cyclohexanone to β-Nitrostyrenes by Using 1-(Trimethylsiloxy)cyclohexene/Dichloro(diisopropoxy)titanium. Preliminary Communication (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 319-324 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Induced by a stoichiometric excess of dichloro(diisopropoxy)titanium, 1-(trimethylsiloxy)cyclohexene and p-substituted β-nitrostyrenes (Y = H,CH3,CH3O,CN) combine in CH2Cl2 solution at -90° preferentially with relative topicity ul - opposite to the corresponding reaction of enolates or enamines. The primary products are the bicyclic nitronates 3-5 which can be separated, and which are cleaved by KF in MeOH to give the aryl(nitroethyl)-substituted cyclohexanones 1 and 2 (Tables 1 and 2, two typical procedures are given). The major products (2:1 to 4:1) are the hitherto not readily available diastereoisomers 2 of l-configuration. Instead of being solvolyzed, the bicyclic nitronate 5 can be used for nitroaldol additions (→6) and for [3 + 2]-dipolar cycloadditions (→7), diastereoselectively furnishing products with 4 asymmetric C-atoms (not counting acetal centers). The Michael addition described here is yet another example of an ul-combination of trigonal centers induced by Lewis acids, overriding the influence of the configuration of the donor component.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19850680205
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  • 170
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    Synthesis and Diels-Alder Reactivity of 1-(Dimethoxy)methyl-2,3,5,6-tetramethylidene-7-oxabicyclo[2.2.1]heptaneInteraction between non-conjugated chromophores, Part 22; Part 21; [1]; Part 20; [2].. Preliminary communication (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 334-337 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A short synthesis of the title compound 13 is reported. The acetal group in 13 enables one to control the regio- and stereoselectivity of the two successive Diels-Alder additions of the tetraene. The first addition is significantly faster than the second one, thus making 13 a versatile reagent for regio- and stereoselective ‘tandem’ cycloadditions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680207
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  • 171
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    Investigation of the Cyclopentenone Formation via the α-Alkynone Cyclisation: Synthesis of the Acorone Intermediate 8-Methylspiro[4.5]deca-3,7-dien-2-one (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 338-344 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As a further application of the cyclopentenone formation A→C via the thermal α-alkynone cyclisation B→C and in order to test the fate of an isolated C,C-double bond within a molecule under these conditions, we investigated the synthesis of the acorone intermediate 3starting from the known carboxylic acid 1. The α-alkynone 2 was obtained from 1 via the acyl chloride 6 and a Pd(II)-catalysed route (22%). The thermolysis of 2 at 550° provided the target molecule 3 (48%) together with the product 9 (20%) of a competing intramolecular ene reaction and its dimer 10 (4%). At a higher thermolysis temperature (650°), the spiro ketone 3 was found to be unstable, affording the retro-Diels-Alder fragments 4-methylidene-2-cyclopentenone (12) (33%) and isoprene (32%). A further example of the influence of an isolated double bond on the yield of the cyclopentenone-formation sequence A→C was provided by the comparison of the annelation 14→20 (5% overall with Pd(II)-catalysed acylation) with that of its non-olefinic analogue 17→21 (53% overall with Friedel-Crafts acylation).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680208
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  • 172
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    The Molecular Ion of 5-Methylene-1,3-cyclohexadiene: Electronic Absorption Spectrum and Revised Enthalpy of Formation (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 345-354 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The title compound (1) is prepared in situ from 5-methylenebicyclo[2.2.0]hex-2-ene by pyrolysis and subsequent photoionization in a photoelectron spectrometer or by X-ray irradiation in an Ar matrix where its electronic absorption spectrum is obtained. The results confirm earlier conjectures that the title cation exists as a distinct entity on the C7H8+ hypersurface and can be obtained photochemically from other isomeric ions or by a McLafferty rearrangement. The enthalpies of formation of 1, its precursor and the corresponding radical ions are compared to the most recent data available for other C7H8 isomers and their ions. It is shown that the thermodynamic stability of 1+ is closer to that of toluene cation than concluded on the basis of earlier results.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680209
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  • 173
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    The Radical Anions of [2.2]Paracyclophane-1,9-diene and Some of its Derivatives. An Unexpected Conformational InterconversionDedicated to Prof. Virgil Boekelheide on the occasion of his 65th birthday (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 377-390 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The radical anions of [2.2]paracyclophane-1,9-diene (2) and its 1,10,12,13,15,16-hexadeuterio derivative 2-D6, as well as those of 4,5,7,8-tetramethyl[2.2]paracyclophane-1,9-diene (3) and its 12,13,15,16-tetradeuterio derivative 3-D4, have been studied by ESR spectroscopy. The coupling constants for 2-· at 178 K are 0.422 mT for four equivalent olefinic protons and 0.046 and 0.020 mT, each for a set of four equivalent aromatic protons. This hyperfine pattern is consistent with either benzene ring bearing two pairs of equivalent protons and it points to a lowering of the anticipated D2h symmetry. The ESR spectra of 2-· are strongly temperature dependent, due to modulation of the two coupling constants of 0.046 and 0.020 mT; these have opposite signs and average to 0.013 mT at 273 K. The experimental findings are interpreted in terms of a transition state of D2h symmetry, 33 kJ/mol above two interconverting equivalent conformations of lower symmetry. Several pieces of evidence suggest that this symmetry is D2, i.e., the benzene rings in 2-· are twisted in opposite directions about the vertical axis. Temperature dependence of the ESR spectra, resulting from modulation of the hyperfine interactions with the aromatic protons, is also observed for 2-D6-· and 3-·. In the case of 3-·, the olefinic protons are, as expected, only equivalent in pairs, the pertinent coupling constants being 0.560 and 0.325 mT. Upon standing at low temperatures, 2-· and 3-· gradually convert into the radical anions of [2.2]paracyclophane (1) and its 4,5,7,8-tetramethyl derivative, respectively. At higher temperatures, cleavage of one bridging chain in 2-· also occurs, with the formation of the radical anion of (E)-4,4′-dimethylstilbene (7). Both reactions of 2-· must involve the transient radical anion of [2.2]paracyclophane-1-ene (4) as proved by the observation of the spectra of 1-· and 7-· with 4 as the starting material.
    Additional Material: 10 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19850680212
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  • 174
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    Light-Induced and Thermal π-Skeletal Rearrangement of Heptalenes with Retention of ConfigurationPresented in part by H.-J. H. at lectures in Vienna (1982), Berlin (1982), Lodz (1984), and Zurich (1985). (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 429-438 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that dimethyl 5, 6, 8, 10-tetramethyl- (3) and 8- (tert-butyl)-5,6,10-trimethylheptalene-1, 2-dicarboxylate (5), and their derivatives rearrange reversibly on irradiation or on heating to yield the corresponding 1,6,8,10-tetramethyl- (4) and 8-(tert-butyl)-1,6,10-trimethylheptalene-1,2-dicarboxylate (6), and their derivatives by double-bond shift (π-skeletal rearrangement) via a transition state with D2 symmetry as the highest possible one. This follows from the fact that (-)-(P)-3 is photochemically as well as thermally rearranged to give (-)-(P)-4 i.e. the π-skeletal rearrangement occurs with retention of configuration of the heptalene skeleton and without loss of optical purity.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19850680216
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  • 175
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    Acid-Catalysed Rearrangements of α-Vinylcyclobutanones (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 439-449 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The BF3 · Et2O- and the CH3SO3H-catalysed rearrangements of 10 α-vinylcyclobutanones have been examined. With little acid, the β,β-dialkyl derivatives 1 were transformed into linear dienones 2 and 3; with more acid, they were converted into cyclopentenones 4 by Nazarov cyclisation of initially formed 2/3. The β-monoalkyl (including the β,γ-dialkyl) derivatives 7 rearranged only with a high acid concentration to afford the cyclopentenones 8 by 1,2-acyl migration. In the case of 7a, the cyclopentenone 8a was accompanied by the unexpected constitutional isomer 9a, which is explained by a reversible interconversion of the cyclobutanone 7a with its isomer 19 via a cyclopropane intermediate like 18. In the case of the β,β-dialkyl derivative 5, which contains an α-isobutenyl (instead of an α-vinyl) group, the acid-catalysed rearrangement product was the bicyclo[3. 1. 0]hexanone derivative 6.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680217
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  • 176
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    First Optically Active Heptalenes and their Absolute ConfigurationPresented in part by H.-J. H. at lectures in Basle (1980), Vienna (1982), Berlin (1982), Lodz (1984), and Zurich (1985). (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 415-428 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: It is shown that dimethyl 7-isopropyl-5, 10-dimethylheptalene-1, 2-dicarboxylate (1) and dimethyl 5, 6, 8, 10-tetramethylheptalene-1, 2-dicarboxylate (2) can be resolved via the corresponding mono-acids and with the aid of optically active primary or secondary amines such as 1-phenylethylamine or ephedrine into the (-)-(P)- and (+)-(M)-enantiomeres, respectively. Characteristic for the (P)-chirality of the heptalene π-skeleton with C2 or pseudo-C2 symmetry are two (-)-CE's at the long wavelength region (450-300 nm) followed by at least one intense (+)-CE at wavelengths about or below 300 nm. The absolute configuration of the heptalenes was correlated with the well-established absolute configuration of (+)-(R)- and (-)-(S)-1-phenylethanol.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19850680215
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  • 177
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    Nucleoside und NucleotideTeil 21: [1].. Teil 22. Synthese eines Tridecanucleosiddodecaphosphats, das die unnatürliche Base 2(1H)-Pyrimidinon enthält (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 475-483 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nucleosides and Nucleotides. Part 22. Synthesis of a Tridecanucleoside Dodecaphosphate Containing the Unnatural Base 2(1H)-PyrimidinoneThe tridecanucleosid dodecaphosphate d(TpTpMpCpGpTpCpApApApApTpC incorporating the modified nucleoside 1-(2′-deoxy-β-D-ribofuranosyl)-2(1H)-pyrimidione (Md, 2) was synthesized using the triester method. The intermediates were the suitably protected trimer d(TpTpM) and the pentamer d(TpTpMpCpG). The latter was condensed with the protected octamer d(TpCpApApApApTpC) to yield the desired tridecanucleotide.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19850680221
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  • 178
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    Synthese macrocyclischer Lactame aus Ketonen durch RingerweiterungHerrn Prof. Dr. Karl Bernauer zum 60. Geburtstag gewidmet (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 484-492 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Synthesis of Macrocyclic Lactams from Ketones by Ring Enlargement ReactionA general synthesis of N-unsubstituted and N-alkyllactams of general structure III is given. Starting materials for this conversion are the aldehydes of general structure I which, by reductive amination, are converted to the corresponding amines II. Under base catalysis, the ring enlargement II→III takes place (Scheme 3).
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    URL: http://dx.doi.org/10.1002/hlca.19850680222
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  • 179
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    Selektive Reaktionen an den Tetranortriterpenen Bussein A und B (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 522-533 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Selective Reactions of the Tetranortriterpenes Busseins A und BBussein A (1) was transformed to the 1′-O- and 2-O-acetyl and the 1′-O - and 2-O-chloroacetyl derivatives 3,5,4, and 6, respectively. By hydrolysis with H2SO4 in MeOH bussein J (7) was obtained from 1 and bussein K (8) from bussein B (2). Treatment of 1 with H2SO4 in H2O and tetrahydrofuran yielded 7, the acid 9, and the dilactone 16. Hydrolysis of 1 with aqueous NH3 in MeOH gave 10; at higher temperature, 12, 13, and 14 were obtained as additional products. With NaOH in aqueous MeOH 7, 10, 15, and 17 - the latter being an isomer of 15 of unknown structure - were formed from 1. Photooxidation of 1 led to 20β,21β:21β,23β-diepoxybussein A (18).
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19850680225
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  • 180
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    Mitteilungen - Communications (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 545-548 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680227
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  • 181
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    Masthead (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680301
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  • 182
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    Stoffwechselprodukte von Mikroorganismen. 232. Mitteilung231. Mitteilung: [1].. (E)-3-(1H-Pyrrol-3-yl)-2-propensäure und (E)-3-(1H-Pyrrol-3-yl)-2-propensäureamid aus Streptomyces parvulus, Stamm Tü 2480 (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 559-562 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: (E)-3-(1H-Pyrrol-3-yl)-2-propenoic Acid and (E)-3-(1H-Pyrrol-3-yl)-2-propenamide from Streptomyces parvulus, Strain Tü 2480The title compounds were isolated from cultures of Streptomyces parvulus. They give a deep blue colour reaction with Ehrlich reagent. Their structures were elucidated by spectroscopy and comparison with synthetic samples. They do not show any antimicrobial activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680304
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  • 183
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    Conformational Studies on Potential β-Turn-Forming Model Peptides (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 705-714 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The conformational behavior of POE-bound model peptides Boc-(L-Ala)2-X-Y-(L-Ala)2-NHPOE (X - Y = L-Pro-Gly (I), Gly-L-Ile (II); NHPOE = aminopoly(oxyethylene)) as well as of the repetitive hexapeptide of elastin, Boc-L-Val-L-Ala-L-Pro-Gly-L-Val-Gly-A-NHPOE-M (III) (A = photosensitive 3-nitro-4-(bromomethyl)benzoyl group; NHPOE-M = aminopoly(oxyethylane) monomethyl ether) has been studied by means of 1H-NMR and CD spectroscopy. Compounds I and III form a β-turn with Pro and Gly in positions i + 1 and i + 2, respectively, while an aggregated state for II, has been identified. The results are in good agreement with published prediction codes giving experimental evidence for the dominance of short-range interactions to establish secondary structure in solution.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19850680320
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  • 184
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    Total Synthesis of (-)-Crinine. Use of Tandem Cationic Aza-Cope Rearrangement/Mannich Cyclizations for the Synthesis of Enantiomerically Pure Amaryllidaceae AlkaloidsPart 14 in the series ‘Synthesis Applications of Aza-Cope Rearrangements’; for Part 13, see [1].Dedicated to the memory of Professor R. V. Stevens (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 745-749 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The total synthesis of enantiomerically pure (-)-crinine (1) in 10 steps and 6% overall yield from cyclopentene oxide is reported. The key step was the rearrangement of 7 upon reaction with AgNO3 at 25°C to give cis-perhydroindolone 8 in 81% yield.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680324
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  • 185
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    Synthesis and Antagonistic Activity of Two Covalently Linked Dimers of Adrenocorticotropin-(11-24)-tetradecapeptide (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 770-776 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The chemical synthesis of two dimers of the sequence 11 to 24 of adrenocorticotropin is described. The two monomers were covalently linked through their N-or C-termini, respectively, using N-acetylglutamic acid or lysine amide as spacers. Compared to the monomer, the first dimer showed moderately, the second strongly increased inhibitory potency upon steroidogenesis in isolated adrenal cells.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19850680327
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  • 186
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    The adamantane rearrangement of 1,2-trimethylenenorbornanes. Part VFor Part IV, see [1].. Rearrangements of 1,2-trimethylenenorbornanes initiated by regioselective formation of carbocation centers at C(2) and C(6) (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 734-744 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The behaviour of the regioselectively generated carbocation centers at C(2) and C(6) in 1,2-trimethylenenorbornanes was investigated in order to study the occurrence or absence of a degenerate rearrangement E⇄M in the adamantane rearrangement of both 1,2-endo- (1) and 1,2-exo-trimethylenenorbornane (2) to 2-endo,6-endo-trimethylenenorbornane (3). A degenerate rearrangement E⇄M is inevitably involved inasmuch as a 1,2-trimethylenenorborn-2-yl cation E not only is formed directly as manifested by the conversions of the reactants 4 (C(2), C(3)-olefin) and 6 (C(2), C(3′)-olefin), but also indirectly (via F→E) if the leaving group at C(6) to be ionized occupies the endo-position (6-endo-alcohol 8). No degenerate rearrangement E⇄M is operative starting from reactants that lead directly to a 2,6-trimethylenenorborn-2-yl cation G; this is the case with both the ionization of the 6-exo-alcohol 10 having the leaving OH-group in a stereoelectronically favoured configuration to undergo simultaneous C(1), C(2)-bond migration (→G) as well as the protonation of the olefin 13 which is followed by same reaction pathway.
    Additional Material: 1 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19850680323
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  • 187
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    Isomérisation cis-trans en Série Alkyl-4-vinyl-3-pipéridine par Sigmatropie [3.3]. Synthèse des Epivinyl Isomères des Alcaloïdes du Quinquina (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 789-800 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: cis, trans Isomerization of 4-Alkyl-3-vinylpiperidines by [3.3] Sigmatropic Rearrangement. Synthesis of Epivinyl Isomers of Cinchona AlkaloidsIsomerization of 4-alkyl-3-vinylpiperidines induced by formaldehyde has been studied for ethyl meroquinate and quinotoxine. The equilibration of cis- and trans-isomers occurs by involvement of a [3.3] sigmatropic rearrangement. This process permits an easy access to the trans-isomers from natural products of cis-configuration and has been used to obtain the epivinyl isomers of cinchona alkaloids.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19850680329
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  • 188
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    Konformation und Dynamik von [6]Paracyclophan-8,9-dicarbonsäure-dimethylester. Eine 1H- und 13C-NMR StudieHerrn Prof. Dr. Dr. h.c. mult. G. Wilke zum 60. Geburtstag gewidmet (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 801-812 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Conformation and Dynamics of Dimethyl [6]Paracyclophane-8,9-dicarboxylate. A 1H- and 13C-NMR StudyThe 1H- und 13C-NMR spectra of dimethyl [6]paracyclophane-8,9-dicarboxylate have been assigned and analyzed in the slow-exchange limit (-20°C) for the ring-inversion process of the methylene bridge using several 2D-NMR techniques. The vicinal 1H, 1H coupling constants of the methylene chain show a Karplus-type dependence on torsional angles. The observed values indicate that the solution conformation of 1 closely resembles that found in the crystal. No significant changes in the 1H-NMR shielding properties of the boat-shaped benzene ring were detected. The 13C chemical shifts of the methylene C-atoms can be explained without invoking ring current contributions, which are too small for unambiguous identification. A lineshape analysis for the AB⇌BA exchange system of the aromatic protons yielded ΔH≠ = 43.25 ± 0.72 kJ/mol, ΔS≠ = -51.27 ± 2.66 J/K mol, and ΔG≠(298) = 58.53 kJ/mol for the dynamic process corresponding to an inversion of the methylene bridge.
    Additional Material: 8 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19850680330
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  • 189
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    Masthead (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985) 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680401
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  • 190
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    Deoxy-nitrosugars. 10th Communication9th Communication: [1].. Synthesis of Isosteric Phosphonate Analogues of Ulose-1-Phosphates (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 819-830 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A general approach to isosteric phosphonate analogues of ulose-l-phosphates is described. A base-catalysed chain elongation via a Michael addition of 1-deoxy-1-nitro-sugars 4, 8, and 16 to the vinylphosphonate 18 followed by hydrolysis of the nitro adducts gave the analogues of D-ribulose-1-phosphate, D-fructose-1-phosphate, and D-sedoheptulose-1,7-diphosphate 21, 23, and 27, respectively, in high yields.
    Additional Material: 2 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19850680402
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  • 191
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    Aromatic nucleophilic substitution. Part 2Part 1: see [1].. Preparation of novel 3-substituted xanthone and thioxanthone derivativesPresented in part at the Herbstversammlung der Schweizerischen Chemischen Gesellschaft, Berne, October, 1981. (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 854-859 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The novel 3-nitro-9-oxo-9H-xanthene- and 3-nitro-9-oxo-9H-thioxanthene-l-carboxylic acids 2a-d were prepared by intramolecular acylation of 3-aryloxy- and 3-arylthio-5-nitrophthalic anhydrides 1 (Scheme). The 3-nitro group was readily substituted by O- and S-nucleophiles and halide and azide ions to give a range of 3-substituted thioxanthone derivatives 3 with varied λmax.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19850680406
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  • 192
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    Synthesen von Dibenzo[b,e][1,4]dioxin-2,3-chinonen, einschliesslich der Ecklonochinone A und B sowie der Isoecklonochinone A und B (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 860-881 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Syntheses of Dibenzo[b,e][1,4]dioxin-2,3-quinones Including the Ecklonoquinones A and B and the Isoecklonoquinones A and BOxidation of monomesyloxy-substituted pyrocatechols with MnO2 in toluene using phase-transfer conditions leads in high yield to monomesyloxy-substituted dibenzo[b,e][1,4]dioxin-2,3-quinones with loss of one mesyloxy group. In this way, ecklonoquinone A (2), ecklonoquinone B (3), isoecklonoquinone A (43), and isoecklonoquinone B (44) were prepared. Their structures are based on X-ray analyses of ecklonoquinone-A leucoacetate (45) and the mesyloxy-substituted quinone 20. The reddish-violet dibenzodioxin-diquinone 49 was prepared from an intermediate of the iso-series. The parent compound 1 has been synthesized in yields better than 50% from pyrocatechol and methyl 2,5-dioxo-2,5-dihydrobenzoate as oxidant and 2-methoxypyridin as catalyst. To rationalize the specific effect on the dimerisation step of the mesyloxy group, the intermediacy of 1,4-quinone monoacetals is proposed. This also applies to a proposed biogenetic scheme.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19850680407
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  • 193
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    Inductive Charge Dispersal in Quinuclidinium Ions. Polar Effects, Part 13 (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 882-886 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Inductive charge dispersal to the α- β- and γ-positions of the solvated quinuclidinium ion has been examined by comparing the pKa and the derived inductivities ρI of several 2- 3- and 4-substituted quinuclidinium perchlorates 4, 5, and 6, respectively. The same inductivity is observed at the practically equidistant β- and γ-positions. It, therefore, appears that polar substituent effects are transmitted directly through the molecule. As expected, inductivity is considerably higher at the α-positions where through-bond and direct induction coincide. The fact that the pKa of all three series of salts correlate linearly with each other points to the common nature of these inductive electron displacements.
    Additional Material: 2 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19850680408
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  • 194
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    Transferts d'hydrogènes dans les cations radicaux ethylène-acetals dérivés de cyclopentanones et cyclohexanones (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 903-911 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Hydrogen Transfer during Decompositions of Molecular Ions of Acetals Derived from Substituted Cyclopentanones and CyclohexanonesThe isomerisation process of ethylene-acetal radical ions of low internal energy has been reinvestigated in more detail. The ring contraction of cyclohexane derivatives into methylcyclopentanes is quite general for these ions. The relative rates of [1, n] H transfers to the C free radical resulting from C—C cleavage α to the acetal group plays the most important part in the mechanism.
    Additional Material: 5 Tab.
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    URL: http://dx.doi.org/10.1002/hlca.19850680412
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  • 195
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    Laser Flash Photolysis of Chloranil in SolutionDedicated to Prof. Albert Eschenmoser on the occasion of his 60th birthday (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 912-918 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chloranil (2,3,5,6-tetrachloro-2,5-cyclohexadiene-1,4-dione; C) in deoxygenated acetonitrile shows transient absorptions which are assigned to the radical anion \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {C}^{- \kern-4pt {.}} $\end{document} and to the triplet 3C*. The absorption due to \documentclass{article}\pagestyle{empty}\begin{document}$ \rm {C}^{- \kern-4pt {.}} $\end{document} rises ‘instantly’ during the 12 ns laser flash and then more gradually in a time of μs. This observation is explained as electron capture from neat acetonitrile by photoexcited C taking place from both its singlet and triplet states with rate constants estimated as 109 and 104 s-1 M-1, respectively.
    Additional Material: 7 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19850680413
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  • 196
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    Photochemical reactions. 144th Communication143rd Communication : [1].. Photochemistry of 5,6-epoxy-1,3-dienes in the ionone series: Influence of a methoxy group in position 7 (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 919-929 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: On triplet excitation (λ 〉 280 nm, acetone), the epoxydiene (E)-5 undergoes initial cleavage of the C(5)—O bond of the oxirane and subsequent cleavage of the C(6)—C(7) bond leading to the diradical intermediate e which reacts by recombination furnishing the cyclic compounds (E/Z)-6, (E/Z)-7,8, and 9. Alternatively, a H-shift leads to the aliphatic methyl-enol ether 10 which undergoes a photochemical [2+2]-cycloaddition to compounds 12 and 13, the main products on triplet excitation of (E)-5. On singlet excitation (λ = 254 nm, MeCN), (E)-5 undergoes cleavage to the carbene intermediates f and g. The vinyl carbene f reacts with the adjacent double bond furnishing the cyclopropene 14 as the main product. From the carbene intermediate g, the methyl-enol ether 15 arises by carbene insertion into the neighboring C—H bond. Furthermore, the diastereomer of the starting material, the epoxydiene (E)-16, and compounds 17A+B are formed via the ylide intermediate h. Finally, the cyclobutene 18 is the product of an electrocyclic reaction of the diene side chain.
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    URL: http://dx.doi.org/10.1002/hlca.19850680414
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  • 197
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    Makrocyclische Ionophore beruhend auf oligomeren Terephthaldiamiden mit von Gastmolekülen abhängiger Selektivität (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 940-944 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Macrocyclic Oligolactams Based on Terephthalic Acid as Ionophores with Selectivity Depending on Included Guest MoleculesMacrocyclic 20- to 60-membered oligolactam hosts exhibit ion selectivities in poly(vinyl chloride) membranes which depend on the ring size and on the substituents of the amide N-atoms. The selectivity may be changed by loading the macrocyclic host with CHCl3 as guest molecule.
    Additional Material: 4 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19850680416
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  • 198
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    The Synthesis and Some Physical Properties of New Laterally Substituted Phenyl Ethers Containing a trans-1,4-Disubstituted Cyclohexane Ring (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 813-817 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis, liquid-crystal transition temperatures, and some physical properties of a variety of substituted phenyl ethers, most of which incorporate a lateral substituent, are reported. Many of the liquid crystals described exhibit nematic phases with negative dielectric anisotropy at elevated temperatures. The relationship between the nature of the lateral substituents and the observed liquid crystal phases and transition temperatures is discussed.
    Additional Material: 1 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19850680331
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  • 199
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    Nature et stabilité des complexes métalliques de cryptands dinucléants en solution. III. Le monocycle [22]-Py2N4 (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 840-845 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nature and Stability of Some Metallic Complexes of Dinucleating Cryptands in Solution III. The Monocycle [22]-Py2N4The nature and stability of complexes formed by a new 22-membered monocycle L = [22]-Py2N4 with the cations Mn+ = Cu2+, Co2+, Ni2+, Zn2+, Cd2+, Pb2+, and Ag+ have been determined in aqueous solutions (0.01M NaClO4, 25°) by pH-metry and also, for the copper system, by UV-absorption spectrophotometry. The stepwise protonation constants of the four amine functions of L were 9.1, 8.3, 7.1 and 3.7 logarithms units, respectively. No evidence was found for the protonation of the two pyridine nitrogen atoms. Mononuclear complexes MLn+ were identified in all systems investigated, but the dinuclear species M2L2n+ were only found with Cu2+ and Ag+. The logarithms of the overall stability constants for the copper and silver complexes are CuL2+, 12.9; Cu2L4+, 18.6; Agl+, 6.3; Ag2L2+, 10.9, respectively. Mononuclear hydroxy species MLOH(n-1)+ were identified in all systems except those of copper and silver. No dinuclear hydroxy complexes were detected. The complexing properties of L are compared to those of the large and less rigid bis-dien.
    Additional Material: 3 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19850680404
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  • 200
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    Nature et stabilité des complexes métalliques de cryptands dinucléants en solution II. Polythiamacrotricycles et monocycles apparentés (1985)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 68 (1985), S. 831-839 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nature and Stability of Some Metallic Complexes of Dinucleating Cryptands in Solution II. Polythiamacrotricycles and Related Monocyclic SubunitsThe stability constants of the Cu2+ and Ag+ complexes of the cylindrical macrotricycle 1a (1,7,13,19-tetraaza 4,16-dioxa 10,22,27,32-tetrathiatricyclo[17.5.5.5]tetratriacontane) have been determined by pH-metry, as well as those of the Cu2+, Co2+, Zn2+, Cd2+, Pb2+, and Ag+ complexes of the monocyclic subunit 2a (1,7-dimethyl-1,7-diaza 4,10-dithiacyclododecane), in aqueous solutions (NaClO4) at 25°. In the Cu(II) systems, equilibria were reached slowly, and the results established by pH-metry were confirmed by UV/VIS spectrophotometric studies. The tricycle 1a forms dinuclear cryptates with copper and silver, with overall stability constants log β210 (Cu2-1a)4+ = 18.5, log β21-2 (Cu2-1a(OH)2)2+ = 4.8, log β210(Ag2-1a)2+ = 23.0. Ag+ also forms a mononuclear (Ag-1a)+ complex, with log β110 = 13.1, but no mononuclear species were detected in the Cu-1a system. The absorption spectra of the bis-Cu(II) complexes of 1a and 2a in aqueous medium, MeOH and propylene carbonate (PC) are given, as well as those, in MeOH and PC, of the bis-copper complexes of the related monocycles 3 and 4 (1,7-diaza-4,10,13-trithiacyclopentadecane and 1.10-diaza 4,7,13,16-tetrathiacyclooctadecane, respectively), and tricycle 5 with two benzyl groups in the lateral chains.The complexing properties of the polyoxa- and polythia macrotricycles (Parts I and II of this series) are compared to those of other bis-chelating ligands, the bicyclic bis-tren and the monocyclic bis-dien.
    Additional Material: 5 Ill.
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    URL: http://dx.doi.org/10.1002/hlca.19850680403
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