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  • 11
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1974 (1974), S. 1895-1907 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Enol Ethers, XII1). - Reactions of Cyclopropylolefins and Enol Ethers with Organic AzidesΔ1-Triazolines 3 are formed from cyclopropylolefins 2 and p-nitrophenylazide (1a). Enol ethers 4 react with 1a at 50°C to yield either Δ1-triazolines 3d-f and/or N-(p-nitrophenyl)-imidic esters 5a-i, while reaction with tosyl azide(1b) at room temperature affords N-tosylimidic esters 6. - Reaction of 4 with 1 primarily yields Δ1-triazolines 3; the secondary reactions of 3 are discussed in terms of substituent effects and reaction conditions. Elimination of N2 from 3 may proceed via the zwitterion I. This reaction becomes easier the better the resulting carbocation II is stabilized.
    Notes: Cyclopropylolefine 2 bilden mit p-Nitrophenylazid (1a) in der Hitze Δ1-Triazoline 3. Enoläther 4 reagieren mit 1a bei 50°C in Abhängigkeit von ihrer Struktur und der Reaktionszeit zu Δ1-Triazolinen 3d-f und/oder N-(p-Nitrophenyl)imidsäureestern 5d-i, während mit Tosylazid (1b) bereits bei Raumtemperatur N-Tosylimidsäureester 6 entstehen. - Die Umsetzung von 4 mit 1 über primär entstehende 1-Triazoline 3 und deren Folgereaktionen wird in Abhängigkeit von Substituenten und Reaktionsbedingungen diskutiert. Die Weiterreaktion von 3 kann über das Zwitterion I erfolgen, wobei N2 um so leichter abgespalten wird, je besser das hierbei entstehende Carbokation II stabilisiert ist.
    Additional Material: 6 Tab.
    Type of Medium: Electronic Resource
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  • 12
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 729 (1969), S. 246-248 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Enol Ethers, VIII. Reactions of Aldehydes with Electron-rich Alkenes1-Dimethylamino-1-ethoxyethylene (1) and 1,1-dipiperidinoethylene (2) react with aromatic aldehydes 3 to give cinnamamides. Coumarines are obtained on reaction with salicylic aldehydes.
    Notes: 1-Dimethylamino-1-äthoxy-äthylen (1) und 1.1-Dipiperidino-äthylen (2) reagieren mit aromatischen Aldehyden 3 zu Zimtsäureamiden. Mit Salicylaldehyden erhält man in glatter Reaktion Cumarine.
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  • 13
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 673 (1964), S. 88-92 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Bildung von Purinen aus Aminoacetonitrilen und Formamidinacetat erfolgt über intermediär entstehende 4-Amino-imidazole und anschließende Anellierung des Pyrimidinrings.
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  • 14
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 673 (1964), S. 82-87 
    ISSN: 0075-4617
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aus Alkyl(Aryl)amino-acetonitrilen und Formamidinacetal erhält man in einer Stufe 7-substituierte Purine (30-60% d. Th.), die sich mit Alkali in hoher Ausbeute (83-95% d. Th.) zu 4-Amino-5alkyl(aryl)amino-pytrimidinen aufspalten lassen.
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  • 15
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1993 (1993), S. 1303-1311 
    ISSN: 0170-2041
    Keywords: 2-Azidocarboxylates ; Rhenium catalysts ; Peptides ; Amino acids ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amino Acids, 17. - A New Synthesis of Didehydro Dipeptides and Didehydro TripeptidesEsters of N-phthaloyl-protected (R)- or (S)-didehydro dipeptides 5-7 were obtained in good yields by the perrhenate-catalyzed decomposition of 2-azidocarboxylates 1 with N-phthaloyl-protected (R)- or (S)-amino acid chlorides 2 in presence of at least equimolar amounts of N-methyl-2-pyridone (4) as acylation catalyst. Esters of didehydro tripeptides 16 were obtained in a comparable procedure from the optically active amino acid chlorides 2 and 2-(2-azidoacyl)amino acid esters 15, which were prepared from 2-azidocarboxylic acids 12 or the corresponding chlorides 13 with 2-amino acid ester hydrochlorides (S)-14. - As an example, the unprotected (S)-alanly-didehydrovalin 20 was prepared from the didehydro dipeptide 18a without any racemization by hydrolysis of the benzyl ester and subsequent hydrogenolytic removal of the N-phthaloyl group.
    Additional Material: 7 Tab.
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  • 16
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1994 (1994), S. 1069-1074 
    ISSN: 0170-2041
    Keywords: 2-Azidocarboxylates ; Rhenium catalyst ; 2-Isocyanato-2-alkenoates ; Amino acids ; Alkenoates ; Diels-Alder reactions ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Amino Acids, 18. - Preparation and Reactions of 2-Isocyanato-2-alkenoates2-Isocyanato-2-alkenoates 3 were obtained in good yields by the perrhenate-catalyzed decomposition of 2-azidoalkanoates 1 in the presence of diphosgene (2a) or phosgene (2b). Methyl 2-azidopropionate (1h) reacts to give a mixture of methyl 2-isocyanato-2-propenoate (3h) and methyl 2-chloro-2-isocyanatopropionate (4). The addition product 4 could easily be converted into 3h by elimination of HCl with triethylamine at 0°C. With benzyl alcohol (5a) and tert-butyl alcohol (5b) the isocyanates 3 react smoothly to give the corresponding Z- or Boc-protected 2,3-didehydroamino acid esters 6 and 7, respectively. The acrylic acid derivative 3h reacts as dienophile with various dienes to yield the Diels-Alder adducts 8-10.
    Additional Material: 6 Tab.
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