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  • 1
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1980 (1980), S. 693-698 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of Heteroaromatic Substituted Ureas and ChloroformamidinesCurtius degradation of heteroaromatic carbonyl azides leads to isocyanates, which react with amines to give the trisubstituted ureas 1. Some of these can be converted into the corresponding chloroformamidines 2 by chlorination with CCl4/(C6H5)3P.
    Notes: Der Curtius-Abbau heteroaromatischer Carbonsäureazide führt zu Isocyanaten, die mit sekundären Aminen zu den trisubstituierten Harnstoffen 1 reagieren. Einige dieser Harnstoffe können durch Chlorierung mit CCl4/(C6H5)3P in die entsprechenden Chlorformamidine 2 übergeführt werden.
    Additional Material: 2 Tab.
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1984 (1984), S. 1180-1192 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: 1,5-Dimethylbicyclo[3.3.0]octane-,6-dione and 1,5-Dimethylbicyclo[3.3.0]octa-3,7-diene-2,6-dione. - Basic Building Blocks for Substituted SemibullvalenesMichael reaction of dimethyl methylmalonate (13) and tert-butyl acrylate (14) affords almost quantitatively the triester 15a which is selectively hydrolyzed to yield the diester-acid 15b. When subjected to Kolbe electrolysis, this produced a 1:1 mixture (28% yield) of the diastereomeric tetraesters rac-12b and meso-12b. After Dieckmann condensation of this mixture followed by hydrolysis of the intermediate β-keto esters 16 and 17 and decarboxylation of the β-keto acids a 93% yield of the bicyclo[3.3.0]octane-2,6-dione 4 and a 61% yield of the crystallized cyclopentanone ester-acid 18 were isolated. On bromination of the diketone 4 using four moles of copper(II) dibromide in chloroform/ethyl acetate as solvent, the α,α′-dibromo diketone 19 is formed as the major product. Dehydrobromination of the crude bromination product of 4 using four moles of copper(II) dibromide in chloroform/ethyl acetate as solvent, the α,α′-dibromo diketone 19 is formed as the major product. Dehydrobromination of the crude bromination product of 4 by means of calcium carbonate in dimethylacetamide as solvent afforded a 67% yield of the α,β-unsaturated diketone 5 besides 4-8% of the unsaturated α-bromo diketone 21. All reactions can be readily carried out on large scale.
    Notes: Michael-Addition von Methylmalonsäure-dimethylester (13) an tert-Butyl-acrylat (14) führt nahezu quantitativ zum Triester 15a, der selektiv zur Diestersäure 15b hydrolysiert wird. Deren Kolbe-Elektrolyse ergibt mit 28% Ausbeute ein (1:1)-Gemisch der diastereomeren Tetraester rac-12b und meso-12b. Nach Dieckmann-Kondensation dieses Gemisches, anschließender Verseifung der intermediären β-Ketoester 16 und 17 und Decarboxylierung der β-Ketosäuren isoliert man 93% Bicyclo[3.3.0]octandion 4 und 61% kristallisierte Cyclopentanonestersäure 18. Bei der Bromierung des Diketons 4 mit 4 mol Kupfer(II)-dibromid in Essigester/Chloroform entsteht hauptsächlich das α,α′-Dibromdiketon 19. Durch Dehydrobromierung des rohen Bromierungsprodukts von 4 mit Calciumcarbonat in Dimethylacetamid erhält man 67% α,β-ungesättigtes Diketon 5 und 4-8% ungesättigtes α-Bromdiketon 21. Alle Reaktionen können sehr einfach im größeren Maßstab durchgeführt werden.
    Additional Material: 2 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1978 (1978), S. 427-430 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of Pseudouridine CPseudouridine C [5-(β-D-ribofuranosyl)uracyl, 6b] has been prepared in an overall yield of 9% (based on 4-bromouracil) by a seven-step synthesis starting from D-ribose (as derivative 3) and 5-bromouracil. By addition, pseudouridines AF, SS (5a, b), and B (6a) are also obtained in a joint total yield of about 30%.
    Notes: Ausgehend von D-Ribose (als Derivat 3) und 5-Bromuracil wird über sieben Stufen PseudouridinC[5-(β-D-Ribofuranosyl)uracil, 6b] in einer Gesamtausbeute von 9% (bezogen auf 5-Bromuracil) dargestellt. Die Pseudouridine AF, AS (5a, b) und B (6a) werden daneben in einer Ausbeute von zusammen rund 30% erhalten.
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  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 438 (1924), S. 202-216 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 45 (1962), S. 504-506 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 17O-NMR spectra of benzofurazan oxide at room temperature show two resonance lines. This adds evidence to support the N-oxide structure to be correct. The 17O spectra are dependent on temperature, due to an equilibration. The average lifetime of the tautomers is of the order of 10-4 s at + 45°C. The activation energy of the equilibrium is found to be 17,2 ± 1,5 kcal/mole and the frequency factor is 3 · 1014 to 3 · 1016 s-1.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 44 (1961), S. 865-880 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Measurements of 17O-NMR-chemical shifts (relative to H2O) have been carried out in a variety of 125 compounds of which 115 are organic.1The resonance of singly bonded oxygen is shifted to low field by all substituents except CH3. The effects of atoms directly bonded to oxygen increases in the order H, C, S, Cl 〈 N 〈 O. Double bonds —O—C=X (X = C, 0) give rise to considerable shifts, whereas groups bonded to C affect the resonance only slightly.2In carbonyl groups the resonance of doubly bonded oxygen is shifted to high field (relative to acetaldehyde) by all substituents. The effect of heteroatoms bonded to C decreases in the order N 〉 O 〉 F 〉 Cl 〉 Br. Conjugation does not affect the shifts. The chemical shifts of the carbonyl group are sensitive to solvents.3An isotope effect on the chemical shift has been detected in water (H317O/D217O).
    Additional Material: 4 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 106 (1923), S. 17-24 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 25 (1842), S. 105-105 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1980 (1980), S. 699-702 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: New Heterocyclic Compounds from N-(2-Thienyl)chloroformamidines and N-NucleophilesN-(2-Thienyl)chloroformamidines 1a - c form unstable intermediates with nucleophilic reagents. These cyclize by two different mechanisms to give thieno[2,3-d]pyrimidines 2-5. Reactivities and mechanisms are discussed.
    Notes: N-(2-Thienyl)chlorformamidine 1a - c bilden mit geeigneten nucleophilen Reagenzien instabile Zwischenstufen, die nach zwei verschiedenen Mechanismen zu Thieno[2,3-d]pyrimidinen 2-5 cyclisieren. Reaktivitäten und Bildungsmechanismen werden diskutiert.
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