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  • 1
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Metal-π-Complexes of Benzene Derivatives, XV. Bis(η6-naphthalene)chromium(0): X-Ray Structure Determination and Investigation by Nuclear Magnetic Resonance SpectroscopyBis(η6-naphthalene)chromium(0) (2) crystallizes in the space group P21/n with two molecules in the unit cell. The ligands in individual molecules of 2 are syn-oriented. The implied presence of a center of symmetry in 2 is caused by disorder that consists in the statistical occupation by chromium atoms of two equivalent sites between the six membered ring of pairs of parallel naphthalene ligands. The 1H and 13C NMR spectra of 2 are analysed and the spectroscopic parameters are discussed with reference to the respective data of free naphthalene as well as other (η-naphthalene)metal complexes.
    Notes: Bis(η6-naphthalin)chrom(0) (2) kristallisiert in der Raumgruppe P21/n mit zwei Molekülen in der Elementarzelle. Die Liganden in individuellen Molekülen von 2 nehmen dabei eine syn-Anordnung ein. Das Vorliegen eines Symmetriezentrums in 2 wird durch eine Fehlordnung vorgetäuscht, die darin besteht, daß in Paaren parallel angeordneter Naphthalin-Liganden linke und rechte Lücken zwischen den Sechsringen statistisch mit Chromatomen besetzt sind. Die 1H- und 13C-NMR-Spektren von 2 werden analysiert, und die spektroskopischen Parameter werden im Vergleich mit entsprechenden Daten des freien Naphthalins sowie anderer (η-Naphthalin)metall-Komplexe diskutiert.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 113 (1980), S. 995-1009 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions to the Chlorination - Dehydrochlorination of Perhydro-1,4-thiazepin-5-onesThe synthesis of unsaturated derivatives of perhydro-1,4-thiazepin-5-ones 3 is investigated. Depending on the substitution the thiazepin-5-ones 3 thereby react with sulfuryl chloride to yield 7- and 2-chloro derivatives 6 and 7; the latter eliminate hydrogen chloride only in the presence of a base (PVP, 8) to give the Δ2-thiazepines 9a,b,d,e,g, whereas the 7-chloro derivatives in situ afford the Δ6-thiazepines 10a - f, the 1,4-thiazepinium chloride 11c being isolated as intermediate. tert-Butyl hypochlorite forms according to the substituent size and solvent polarity 2- and 7-halogenation products, as well as 1,4-thiazepin-5-one-S-oxides 22. Further halogenation of the Δ6-1,4-thiazepines 10a - c results in the formation of unsaturated halogen derivatives 24, 25, and 26.
    Notes: Es wird versucht, ungesättigte Derivate von Perhydro-1,4-thiazepin-5-onen 3 herzustellen. Die Thiazepin-5-one 3 reagieren dabei je nach Substitution mit Sulfurylchlorid zu 7- und 2-Chlorderivaten 6 und 7; letztere eliminieren Chlorwasserstoff erst in Basen-Gegenwart (PVP, 8) zu den Δ2-Thiazepinen 9a,b,d,e,g, die 7-Chlorderivate dagegen in situ zu den Δ6-Thiazepinen 10a - f, wobei das 1,4-Thiazepinium-chlorid 11c in Substanz erhalten wird. tert-Butylhypochlorit ergibt je nach Substituentengröße und Solvenspolarität neben 2- und 7-Halogenierung auch durch Umlagerung 1,4-Thiazepin-5-on-S-oxide 22. Erneute Halogenierung der Δ6-1,4-Thiazepine 10a - c ergibt die ungesättigten Halogenderivate 24, 25 und 26.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 360-366 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Evidence for 4-Homocubyl Carbenium Ions as Reactive Intermediates4-(Hexafluoroisopropoxy)homocubane (6) is the main product of the thermolysis reaction of N-(4-homocubyl)-N-nitrosoacetamide (9) and of the solvolysis reaction of 4-homocubyl bromide (5) in hexafluoro-2-propanol. This is experimental evidence for 4-homocubyl carbenium ions as intermediates in both reactions. The solvolysis rate of 4-homocubyl bromide at 120°C in the same solvent (k1120°C=1.3 · 10-7s-1) by far exceeds that of 1-norbornyl bromide which does not react at a detectable rate under these conditions. According to force field calculations the strain enthalpy is increasing by as much as 66 kcal · mol-1 in the ionisation of 4-homocubyl bromide. Therefore nonclassical stabilization of the 4-homocubyl carbenium ion is postulated.
    Notes: Bei der Thermolyse von N-(4-Homocubyl)-N-nitrosoacetamid (9) und bei der Solvolyse von 4-Homocubylbromid (5) in Hexafluor-2-propanol entsteht 4-(Hexafluorisopropoxy)homocuban (6) als Hauptprodukt. Dies beweist das Auftrete von 4-Homocubyl-Carbenium-Ionen als Zwischenstufen beider Reaktionen. Die Solvolysegeschwindigkeit von 4-Homocubylbromid bei 120°C in Hexafluor-2-propanol (k1120°C = 1.3 · 10-7 s-1) ist wesentlich höher als die von 1-Norbornylbromid, dessen Solvolyse unter diesen Bedingungen nicht nachweisbar ist. Da die Ionisation von 4-Homocubylbromid nach Kraftfeldrechnungen mit 66 kcal · mol-1 Ansteigen an Spannungsenthalpie verbunden ist, wird für das 4-Homocubyl-Carbenium-Ion eine nichtklassische Stabilisierung angenommen.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 115 (1982), S. 3032-3041 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Introduction of Oxygen Functions into the α-Position of β-Diketones, 8 Ozonolysis of Sulfonium Ylides(Dimethylsulfonio)diacylmethanides 1, prepared by known methods, are cleaved by equimolar amounts of ozone in aprotic medium yielding vicinal triketones 2 and DMSO. Peroxydic reaction products are not detectable.
    Notes: Auf bekannte Weise leicht zugängliche (Dimethylsulfonio)diacylmethanide 1 lassen sich in aprotischem Medium durch äquimolare Mengen Ozon zu vicinalen Triketonen 2 und DMSO spalten. Peroxidische Reaktionsprodukte sind nicht nachweisbar.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1436-1454 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Evidence for a Radical Chain Mechanism for the Knabe Reaction of 1,2-Dihydro-2-methylpapaverineA free radical chain mechanism is proposed for the Knabe reaction and the accompanying elimination reaction on account of their nonintegral reaction order and of successful inhibition experiments. 3,4-Dimethoxybenzyl radicals are the chain carrying species. Battersby's synthesis of N-methylpavine (19) from 1,2-dihydro-2-methylpapaverine (9) is dependent on the presence of formic acid as radical chain inhibitor. In the presence of inhibitors 1-benzyl-1,4-dihydro-2-methyl-isoquinolinium ions like 10 are persistent species whose chemistry can now be investigated.
    Notes: Die Knabe-Reaktion von 1,2-Dihydro-2-methylpapaverin (9) und die begleitende Eliminierungsreaktion wurden durch ihre gebrochene Reaktionsordnung und durch die Möglichkeit der Inhibition als Radikalkettenreaktionen erkannt, deren kettentragendes Radikal das 3,4-Dimethoxybenzylradikal ist. Die Synthese von N-Methylpavin (19) aus 1,2-Dihydro-2-methylpapaverin (9) ist an die Anwesenheit von Ameisensäure als Inhibitor der Radikalketten gebunden. Durch Zusatz von Inhibitoren können nun Immoniumionen 10 und analoge Verbindungen stabilisiert und ihre Chemie untersucht werden.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 2238-2249 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thermolabile Hydrocarbons, XXI. Relationships between Thermal Stability and Strain of Non-Symmetrical Highly Branched HydrocarbonsThe pyrolysis reaction of 20 hydrocarbons 3 into radicals 4 and tert-butyl radicals was investigated by product analysis and kinetics. It is shown that the same relationships between the free enthalpies of activation and the strain energies observed earlier for the cleavage of symmetrically substituted CC bonds are valid for the cleavage of unsymmetrical substituted bonds. The introduction of the new concept „strain energy of dissociation“ (difference in strain between the ground state 3 and the residual strain in the radical fragments 4 and 5) has proven to be particularly useful. It is now possible to predict the rate of homolytic cleavage of almost all simple CC bonds by force field calculations.
    Notes: Die thermische Zerfallsreaktion von 20 Kohlenwasserstoffen 3 zu den Radikalen 4 und tert-Butylradikalen (5) wurde präparativ und kinetisch untersucht. Die früher für die thermische Spaltung symmetrisch substituierter C — C-Bindungen festgestellten quantitativen Beziehungen zwischen den freien Aktivierungsenthalpien und den Spannungsenthalpien können auf unsymmetrisch substituierte C — C-Bindungen übertragen werden. Die Einführung des Begriffs der „Dissoziationsspannung“ (Differenz von Grundzustandsspannung und Restspannung in den radikalischen Bruchstücken) hat sich als besonders vorteilhaft erwiesen. Durch einfache Kraftfeldrechnungen kann nun die thermische Spaltungsgeschwindigkeit der meisten einfachen aliphatischen CC-Bindungen vorausgesagt werden.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1259-1261 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A Simple Synthesis of 5-Cyano-2-pyridinecarboxylic Acid and its AmideThe title compounds 3 and 2 (X = CN) are prepared in good yields by regioselective carbamoylation of 3-cyanopyridine in a Minisci reaction and by consecutive amide hydrolysis with amyl nitrite in HCl-saturated acetic acid. The observed regioselectivity apparently remains confined to carbamoyl and possibly acyl radicals and to - M-effect substituents in 3-position.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Metal π-Complexes of Benzene Derivatives, XXIV1). 1H NMR Coordination Shift and Ring Current Quenching in Sandwich Complexes as Studied for Bis(η6-[10]paracyclophane)chromium(0)The title compound was prepared by means of metal atom-ligand vapor cocondensation. Its most conspicuous feature, the well defined disposition of 20 methylene groups in the periphery of the title complex is employed to gauge via 1H NMR the coordination induced quenching of the aromatic ring current in arenes.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1748-1764 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thermolabile Hydrocarbons, XXII. Thermolysis of symm. Tetraalkyldiarylethanes and the Resonance Energy of α,α-Dialkylbenzyl RadicalsThe products and the activation parameters for the thermolysis reactions of the hydrocarbons 1 - 10 were determined. From correlations between δG† and the ground state strain Hsp or the change in strain during the dissociation process Dsp10) the steric accelleration of this reaction was analyzed quantitatively. A comparison of this analysis with a corresponding correlation for simple Cq - Cq alkanes8) results in a resonance energy of 8.4 ± 1.1 kcal · mol-1 for α,α-dialkylbenzyl radicals. The origin of the appreciable variation of δS† in this series and for the poorer precision of δH†/Hsp correlations is discussed.
    Notes: Die Produkte und die Aktivierungsparameter der Thermolyse der Kohlenwasserstoffe 1 - 10 wurden bestimmt. Die sterische Beschleunigung des Zerfalls dieser Verbindungen in die Radikale 11 wurde aus der Korrelation der δG†-Werte mit der Grundzustandsspannung Hsp bzw. der Dissoziationsspannung Dsp10) quantitativ analysiert. Durch Vergleich dieser Analyse mit der entsprechenden Korrelation der Thermolysedaten einfacher Cq - Cq-Alkane8) ergibt sich für tert. Benzylradikale eine Resonanzenergie von 8.4 ± 1.1 kcal · mol-1. Die Ursachen der beachtlichen Schwankung der δS†-Werte in dieser Reihe und der geringen Präzision der δH†/Hsp-Korrelationen werden diskutiert.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1834-1855 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Functionalised Dioxides (syn-1,4) and Trioxides (anti,anti) of TropilideneTropone (1) is the starting material of a preparatively useful access to C-2 functionalised syn-1,4-tropilidene dioxides (3, 6, 7). Upon highly selective HOCl addition to the syn-1,4-tropone dioxide 3 (80 - 85% 6β, 7α-chlorohydrin 21a) and an unselective reduction step an entry is opened via the 2α-alcohol 35a to the C-8-functionalised anti,anti-tropilidene trioxides (19, 33, 36).
    Notes: Tropon (1) ist Edukt eines präparativ brauchbaren Zugangs in die Reihe der C-2-funktionalisierten syn-1,4-Tropilidendioxide (3, 6, 7). Nach hochselektiver HOCl-Addition an das syn-1,4-Tropondioxid 3 (80 - 85% 6β, 7α-Chlorhydrin 21a) und (unselektiver) Reduktion gelingt über den 2α-Alkohol 35a der Einstieg in die Reihe der C-8-funktionalisierten anti,anti-Tropilidentrioxide (19, 33, 36).
    Type of Medium: Electronic Resource
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