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  • Chemistry  (148)
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  • 1
    Electronic Resource
    Electronic Resource
    Didesoxy-Ribonucleoside durch Schmelzkondensation (1993)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 335 (1993), S. 415-424 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Dideoxy Ribonucleosides by Fusion MethodThe dideoxy nucleosides 2, 4 and 6 are synthesized from the 1-O-acetyl-2,3-dideoxyribose derivatives 1, 3 and 5 by fusion with chlorinated purines and other nitrogen heterocycles at 110-120°C without added catalyst. The 1H-NMR and 13C-NMR spectra of the compounds are given.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19933350504
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  • 2
    Electronic Resource
    Electronic Resource
    N-Funktionalisierte Cyclopentadienid-Anionen; Chloronium- und Bromonium-Cyclopentadienide (1994)
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 336 (1994), S. 145-149 
    Details
    ISSN: 0941-1216
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: N-Functionalized Cyclopentadienide Anions; Chloronium- and Bromonium-Cyclopentadienides2,3-Dicyano-1,4-diethoxycarbonylcyclopentadienide anion (3) is N-functionalized by nitration, nitrosation, azo coupling or diazo-group transfer. Phenylbromonium- and phenyl-chloronium-cyclopentadienes 14 and 15 are synthesized by photolysis of the diazo compound 13 in the appropriate halobenzene.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/prac.19943360208
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  • 3
    Electronic Resource
    Electronic Resource
    1,4-cis-Diaminotetra(di)deoxyheptitols from Tropilidene - a Variable Access to Tropa-Type Heterocycles (1997)
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1997 (1997), S. 1481-1497 
    Details
    ISSN: 0947-3440
    Keywords: 1,4-cis-Diaminotetra(di)deoxyheptitols ; Tropa-type heterocycles ; Total syntheses ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthetic potential of the dianhydrocycloheptenepentols 3 and dianhydrocycloheptaneheptols 4 - ultimately available from tropilidene - as intermediates en route to 1,4-cis-diaminotetra(di)deoxyheptitols is studied. With standard bivalent N nucleophiles (methyl-, benzylamine, hydrazines) the regioselective installation of two (e.g. 9, 34) amino functions has to compete with the generation of variously functionalized tropa-type 8-azabicyclo[3.2.1]octanes (e.g. 29, 30, 35, 45, 47). With azide (N3-) as monovalent nucleophile in unsaturated diepoxides 3 twofold, nearly regiospecific substitution (7) - in competition with [3,3]-sigmatropic migration (SN2′ substitution) -, in saturated diepoxides 4 regioselective monosubstitution (39) can be achieved.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jlac.199719970727
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  • 4
    Electronic Resource
    Electronic Resource
    Nucleosid-5′-carbonsäureester als Modelle für die Konformationsanalyse von Nucleosiden und Nucleotiden (1972)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 105 (1972), S. 642-649 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Esters of Nucleoside-5′-carboxylic Acids as Model Compounds for Conformational Analysis of Nucleosides and NucleotidesN.m.r. studies on the nucleoside-5′-carboxylates 5-8 lead to the detection of two rotamers with respect to the C-N-glycosidic bond. A method to distinguish between these syn- and anti-conformers is found in the influence of the conformational chirality (due to hindered rotation) on diastereotopic protons. The conclusions are augmented by o.r.d. and i.r. spectra. Procedures of esterification of the nucleoside-5′-carboxylic acids 1-4 are described.
    Notes: NMR-Studien an den Nucleosid-5′-carbonsäureestern 5-8 führen zum Auffinden von zwei Rotameren in Bezug auf die glykosidische Bindung. Als Methode zur Unterscheidung zwischen diesen syn- und anti-Konformeren wird der Einfluß der durch die Rotationshinderung bedingten konformativen Chiralität auf diastereotope Protonen herangezogen. Die Schlußfolgerungen werden durch ORD- und IR-Spektren unterstützt. Es werden Verfahren zur Veresterung der Nucleosid-5′-carbonsäuren 1-4 beschrieben.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19721050230
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  • 5
    Electronic Resource
    Electronic Resource
    Synthese und 13 C-NMR-Spektren hochgliedriger Cycloalkadiine (1976)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 109 (1976), S. 497-502 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Syntheses and 13C N.M.R. Spectra of High Membered CycloalkadiynesThe syntheses of cycloalkadiynes 3 with 19 up to 44 ring members by alkylation of the dilithium salts of terminal alkadiynes 2 with α,ω-dibromoalkanes 1 are described. The 13C n. m. r. spectra of 3 are recorded.
    Notes: Hochgliedrige Cycloalkadiine 3 mit 19 bis zu 44 Ringgliedern werden durch Alkylierung der Dilithium-Salze terminaler Alkadiine 2 mit α,ω-Dibromalkanen 1 dargestellt. Die 13C-Kernresonanzspektren von 3 werden kurz diskutiert.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19761090213
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  • 6
    Electronic Resource
    Electronic Resource
    Asterane, XIII Synthese des Tetraasterans durch Photodimerisierung von 3,6-Dihydrophthalsäure-anhydrid (1976)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 109 (1976), S. 3781-3792 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Asteranes, XIII Synthesis of Tetraasterane by Photodimerisation of 3,6-Dihydrophthalic AnhydrideThe cage dimeric tetraasteranetetracarboxylic dianhydride 8 as well as the open trans dimers 6 and 7 have been isolated among monomeric products (2-4) on irradiation 3,6-dihydrophthalic anhydride (1) in ether, acetone, and dioxane. Unsubstituted tetraasterane (pentacyclo-[6.4.0.02,7. 0.4,11 0.5,10]dodecane, 14, is obtained by degradation of tetraasterane-1,4,5,8-tetracarboxylic acid (12) with lead tetraacetate and N-chlorosuccinimide via the tetrachlorotetraasterane 13. The structures of 6 and 12 have been confirmed by X-ray analysis. The influence of substituents on fragmentation patterns of tetraasterane derivatives in the mass spectrometer is indicated.
    Notes: Bei der Belichtung von 3,6-Dihydrophthalsäure-anhydrid (1) in Äther, Aceton und dioxan werden neben monomeren Produkten (2-4) das käfigdimere Tetraasterantetracarbonsäure dianhydrid 8 sowie die offenen trans-Dimeren 6 und 7 isoliert. Der Abbau von Tetraasteran-1,4,5,8-tetracarbonsäure (12) mit Bleitetraacetat und N-Chlorsuccinimid ergibt über das Tetrachlortetraasteran 13, das unsubstituierte Tetraasteran (Pentacyclo[6.4.0.02,7 0.4, 110.5,10]dodecan,14, Die Strukturen von 6 und 12 wurden durch Röntgenanalyse bestätigt. Der Substituenteneinfluß auf den Zerfall von Tetraasteranderivaten im Massenspektrometer wird angedeutet.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19761091205
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  • 7
    Electronic Resource
    Electronic Resource
    Synthese von zweifach überbrückten Tetraamino-1,4-benzochinonen (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 3675-3684 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of Doubly-Bridged Tetraamino-1,4-benzoquinonesStarting with the bridged 2,5-diamino-3,6-dichloro-1,4-benzoquinone 1 the doubly-bridged tetraamino-1,4-benzoquinones 5a-e are synthesised. The reductive acetylation of 5c followed by methylation affords compound 7.
    Notes: Ausgehend von dem einfach überbrückten 2,5-Diamino-3,6-dichlor-1,4-benzochinon 1 werden die zweifach überbrückten Tetraamino-1,4-benzochinone 5a-e synthetisiert. Durch reduktive Acetylierung von 5c und nachfolgende Methylierung wird Verbindung 7 erhalten.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831161115
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  • 8
    Electronic Resource
    Electronic Resource
    Thermolabile Kohlenwasserstoffe, XVIII. 1-Substituierte Neopentyl-Radikale und ihre Dimeren (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 1787-1821 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Thermolabile Hydrocarbons, XVIII, 1-Substituted Neopentyl Radicals and their DimersFive 3,4-diaryl-2,2,5,5-tetramethylhexanes 1a-e were prepared as pure meso- and DL-isomers. According to the NMR spectra, x-ray analyses for meso- and DL-1e (with an (FB)2E conformation10) as energy minimum for DL-1e), and force field calculations the diastereomers have distinctly different minimum energy conformations, rotational potentials, and strain enthalpies. Also the activation parameters for the thermal dissociation into 1-arylneopentyl radicals 2 are typically differing. From an entropy discussion it is concluded that sandwich-like diastereomeric radical complexes are formed in these reactions as first intermediates. Their tightness influences ΔS≠. The recombinations of the radicals 2 likewise take place stereoselectively. The substituent effects on the selectivity can also be understood by primary formation of diastereomeric complexes of radical pairs.
    Notes: Die 3,4-Diaryl-2,2,5,5-tetramethylhexane 1a-e wurden als reine meso- und DL-Isomere dargestellt. Nach NMR-Analyse, Röntgenstrukturbestimmungen für meso- und DL-1e (mit (FB)2E-Konformation10) als Energieminimum für DL-1e) und Kraftfeldrechnungen unterscheiden sich die Diastereomeren charakteristisch in ihren Vorzugskonformationen, Rotationspotentialen und Spannungsenthalpien sowie in den Aktivierungsparametern ihres thermischen Zerfalls in 1-Arylneopentyl-Radikale 2. Aus einer Entropiediskussion wird gefolgert, daß die thermische Dissoziation dabei über primär gebildete diastereomere sandwichartige Radikalkomplexe verläuft, deren Festigkeit ΔS≠ beeinflußt. Die Rekombination der Radikale 2 erfolgt ebenfalls stereoselektiv. Die Substituenteneffekte auf die Selektivität werden durch primäre Bildung der diastereomeren Radikalpaar-Komplexe verständlich.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831160509
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  • 9
    Electronic Resource
    Electronic Resource
    Über den Anwendungsbereich gezielter Catenansynthesen. Verbesserte Synthese von zweifach überbrückten 1,4-Diaminobenzol-Derivaten (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 1866-1872 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Scope and Limitations of Directed Syntheses of Catenanes., Improved Synthesis of Double-Bridged 1,4-Diaminobenzene DerivativesIn a one-flask reaction the double-bridged 1,4-diaminobenzene derivative 4a is synthesized in different solvents from 1,4-diaminobenzene and 1,10-dibromodecane. The highest yields are obtained in 2-pentanol and tert-amyl alcohol. - In a multi-step reaction sequence the [2]-precatenane 10 is synthesised starting from 3,5-tetracosamethylenepyrocatechol (7) and 1,19-dichloro-10-nonadecanone (8). The attempted transformation of this compounds into the corresponding [2]-catenane by splitting the bonds between the aromatic nucleus and the bridgehead atoms was unsuccessful.
    Notes: Das zweifach überbrückte 1,4-Diaminobenzol-Derivat 4a wird in einer Eintopfreaktion in verschiedenen Lösungsmitteln aus 1,4-Diaminobenzol und 1,10-Dibromdecan synthetisiert. Die höchsten Ausbeuten werden in 2-Pentanol- und tert-Amylalkohol erhalten. - In einer mehrstufigen Reaktionsfolge wird das [2]-Praecatenan 10, ausgehend von 3,5-Tetracosamethylenbrenzcatechin (7) und 1,19-Dichlor-10-nonadecanon (8) synthetisiert. Seine Umwandlung in das entsprechende [2]-Catenan durch Spalten der Bindungen zwischen dem aromatischen Kern und den beiden Brückenkopfatomen gelingt nicht mehr.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831160514
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  • 10
    Electronic Resource
    Electronic Resource
    cis,trans-Oxaaza-bis-σ-homobenzole - 4H-1,4-Oxazocine (1983)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 2492-2523 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: cis,trans-Oxaaza-bis-σ-homobenzenes - 4H-1,4-OxazocinesThe cis-oxaaza-bis-σ-homobenzene framework has been synthesised via two routes starting from readily accessible materials (11, 25). As expected the N-SO2R derivatives 3a, b are sufficiently stable to be isolated; on heating, they readily and quantitatively undergo [π2 + σ2 + σ2]-cycloreversion to the 4H-1,4-oxazocines 6a, b (3b: t1/2 (60°C) = 33.2 min; ΔG≠ = 104.0 kJ·mol-1). The latter prefer a non-planar, folded conformation. Using a precursor of 3b (27a), the thermally stable trans-oxaaza-bis-σ-homobenzene 9 was obtained in very small yield (2-6%) by two alternative pathways.
    Notes: Mit jeweils gut zugänglichen Ausgangsmaterialien (11, 25) werden zwei Synthesen für das cis-Oxaaza-bis-σ-homobenzol-Gerüst entwickelt. Die erwartungsgemäß isolierbaren N-SO2R-Derivate 3a, b gehen beim Erwärmen rasch und einheitlich die [π2 + σ2 + σ2]-Cycloreversion in die 4H-1,4-Oxazocine 6a, b ein (3b: t1/2 (60°C) = 33.2 min; ΔG≠ = 104.0kJ. mol-1). Letztere bevorzugen eine nicht-planare, gefaltete Konformation. Ausgehend von einem Synthesezwischenprodukt (27a) wird in zwei Varianten und in jeweils sehr geringer Ausbeute (2-6%) auch das thermisch beständige trans-Oxaaza-bis-β-homobenzol 9 hergestellt.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19831160711
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