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  • 1970-1974  (26)
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 53 (1970), S. 1937-1939 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Herstellung von O,O-Diacetyl-S-2-methylcyclodopa-methylester (7) durch Oxydation von S-2-Methyldopa-methylester (4) und anschliessende Reduktion und Acetylierung ist beschrieben. Im Gegensatz zu Cyclodopa (2) wird 2-Methylcyclodopa-methylester (6) am Stickstoff durch Acetanhydrid und Pyridin nicht acetyliert.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 53 (1970), S. 433-448 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The total synthesis of a neobetanidine derivative (3b) is described.Preliminary experiments led to the synthesis of neobetenamine (4), which presents the ring system of neobetanidine (3). A general method for the synthesis of several compounds containing the essential neobetanidine chromophore (a 1, 7-diazaheptamethine system incorporating a pyridine ring) consisted of Vilsmeier-Haack condensations involving the active (enolizable) methyl group of γ-picoline. Neobetenamine (4) resulted from this reaction with N-formyl-indoline, and also by an amine exchange between indoline and the Vilsmeier-Haack product from γ-picoline and N-methyl-formanilide.The methyl group of γ-picoline-2, 6-dicarboxylic ester 9, however, was resistant to the Vilsmeier-Haack condensation, but could be activated by introduction of a carboxyl into it: 4-chloropyridine-2, 6-dicarboxylic ester (11a) (from chelidamic ester) was used to alkylate malonic ester. The product (12a) lost only one carboxyl group when saponified. The resulting 2, 6-dicarboxy-pyridine-4-acetic acid (13a) readily underwent a novel decarboxylative condensation with the Meerwein acetal of dimethyl formamide to 4-(2-dimethylamino-vinyl)-2, 6-dimethoxycarbonyl-pyridine (14b), the first synthetic derivative of a neobetalaine. The enamine 14b was subjected to amine exchange reactions with indoline to 2-decarboxy-5, 6-dideoxy-neobetanidine dimethyl ester (15), and with (S)-cyclodopa (16) 5, 6-di-O-methyl-neobetanidine trimethyl ester (3b). The latter was identical with the diazomethane transformation product of betanidine (1), the aglucone of the pigment of the red beet, betanine.A few proton resonance and electron spectral properties, as well as the basicities of several of the synthesized compounds, are tabulated and discussed as far as they express special structural and electronic features of the common 1, 7-diazaheptamethine chromophore.
    Additional Material: 4 Tab.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The two isomeric tetrabromides, α-isomer mp. 198° and β-isomer mp. 226° described in [1], are identified as cis, cis, trans-2, 4, 6, 8-tetrabromo-cyclooctane-1, 5-dione (2) and cis, trans, cis-2, 4, 6, 8-tetrabromo-cyclooctane-1, 5-dione (3) by an analysis of their NMR.-spectra which also allows a derivation of their preferred conformations. Both exist in solution as boat-chair conformers, the geometries of which correlate well with the IR.- and UV.-spectra.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Homo-p-chinon (4 = Bicyclo[4.1.0]hept-3-en-2,5-dion) wurde hergestellt und auf seine Spektraleigenschaften untersucht. Die UV.-, IR.- und NMR.-Spektren sind charakteristisch für die darin enthaltene Endion-und cis-disubstituierte Cyclopropan-Substruktur, ohne eine starke Wechselwirkung zwischen den beiden zum Ausdruck zu bringen.Basische Thermolyse des Bis-p-toluolsulfonylhydrazons (9) von Homo-p-chinon ergab das bekannte 1,7 a-Diaza-inden (10). Dies bestätigt den früher postulierten Mechanismus der Bamford-Stevens-Reaktion mit den zwei isomeren Bis-homo-p-chinonen (1a und 2a).
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Doppelte Anlagerungen von Dichlorcarben und von Dibromcarben an Durochinon (1) ergaben 4,4,8,8-Tetrachlor-(3) und 4,4,8,8-Tetrabrom-1,3,5,7-tetramethyl-anti-tricyclo[5.1.0.03,5]octan-2,6-dion (4) (= Tetrachlor- und Tetrabrom-anti-bis-homodurochinon).Die anti-Konfiguration der beiden Diketone 3 und 4 wurde aus einfachen röntgenographischen Daten abgeleitet: Zwei Molekeln in der Elementarzelle und die Raumgruppe P21/n verlangen Zentrosymmetrie für die beiden Molekeln 3 und 4 im Kristallgitter, was die syn-Konfiguration ausschliesst.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 1872-1876 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,3,5,5-Tetramethylcyclohexa-1,3-diene, specifically deuterated in all positions except the gem.-dimethyl groups (11), was synthesized and found to undergo a rearrangement in the gas phase at 560°, which leads to a statistical distribution of the 6 hydrogen atoms to all 16 positions. This shows that the title compound (2) automerizes under these conditions and that the reaction proceeds via a series of ring openings (to 5) followed by degenerate [1,7]-H-shifts and rig closures (back to 2) rather than via [1,5]-CH3-shifts. It is suggested that the previously studied rearrangement of 5,5-dimethylcyclohexa-1,3-diene (1) to 1,5-dimethylcyclohexa-1,3-diene (3) takes its course by the same reaction pathway.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 54 (1971), S. 6-15 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die vor kurzem beschriebenen 6-Trichlormethyl-2-pyrone wurden mit Zink und mit komplexen Metallhydriden reduziert. 6-Trichlormethylpyron (15) und drei an C4 verschieden alkylierte Derivate (5, 16 und 17) ergaben mit Zink in Eisessig die entsprechenden 6-Methyl-2-pyrone 18, 1, 19 und 20. Im Falle des 6-Trichlormethyl-4-(4′-methyl-pent-3′-en-yl)-2-pyrans (17) bildete sich auch 3,8,8-Trimethyl-5,6,7,8-tetrahydro-isocumarin (21).Die komplexen Metallhydrid-Reduktionen wurden am Beispiel des 6-Trichlormethyl-4-methyl-2-pyron (5) untersucht. Mit Natriumborhydrid in Äthanol entstanden 6-Dichlormethyl-4-methyl-2-pyron (6, 14%) und 6,6,6-Trichlor-3-methyl-hex-3-en-1, 5-diol (7, 37%). Mit Lithiumaluminiumhydrid in Tetrahydrofuran erhielt man 6-Chlor- (10, 47%) und 6,6-Dichlor-3-methyl-hexa-3,5-dien-1-ol (9, 19%). Für diese Hydridreduktionen wird ein Mechanismus vorgeschlagen, welcher mit den Produkten der Lithiumaluminiumdeuterid-Reduktion nicht in Widerspruch steht.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 56 (1973), S. 2523-2534 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Eine Synthese von Bicyclo[3.3.1]nonan-3,7,9-trion-9-(äthylen)acetal (6) durch doppelte Michael-Addition von Aceton-dicarbonsäure-dimethylester (9) an Benzochinonmono(äthylen)acetal (8) und anschliessende Verseifung und Decarboxylierung des intermediären 2,4-Dicarbomethoxy-bicyclo[3.3.1]nonan-3,7,9-trion-9-(äthylen)acetals (10) wird beschrieben. Bromierung des Triketon-monoacetals 6 mit Brom in Eisessig liefert 2α,4β,6α,8β-Tetrabrombicyclo [3.3.1]nonan-3,7,9-trion-9-(äthylen)acetal (12), dessen Konfiguration sich aus dem NMR.-Spektrum mit Hilfe von Symmetrieargumenten und aus Vergleichen von chemischen Verschiebungen ergibt. Durch Behandlung des rohen Tetrabromids (12) mit Triäthylamin entsteht ein Gemisch von 2,4-Dibrom- (13) und 2,6-Dibrom-triasteran-3,7,9-trion-9-(äthylen)acetal (14), welches sich einerseits mit Säure zu einem 1:2-Gemisch von 2,4-Dibrom- (15) und 2,6-Dibrom- triasteran-3,7,9-trion (16) hydrolysieren und andererseits mit Tri-n-butyl-zinnhydrid zu Triaste-ran-3,7,9-trion-9-(äthylen)acetal (17) reduktiv debromieren lässt. Hydrolyse des Triketon-mono-acetals (17) oder reduktive Debromierung des Triketodibromid-Gemisches (15 und 16) führt zum hochschmelzenden, in den meisten Lösungsmitteln wenig löslichen Triasteran-3,7,9-trion (4). Die Spektraleigenschaften der erwähnten Substanzen werden diskutiert und zur Bestätigung der Strukturen zugezogen.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 734-748 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The pyrrolidino-aminal (4) of bicyclo[3.1.0]hex-2-ene-6-endo-carbaldehyde (3) underwent a facile (80°), mildly acid catalyzed isomerization to the corresponding exo-aminal (6), which was characterized by hydrolysis to bicyclo[3.1.0]hex-2-ene-6-exo-carbaldehyde (7).At higher temperatures (140°), the two aminals 4 and 6 were converted smoothly to a 1:1 mixture of syn- and anti-4-(pyrrolidino-methylidene)-bicyclo[3.1.0]hex-2-ene (syn- and anti-7-pyrrolidino-homofulvene1) 8 and 9. The structures of 8 and 9 were derived from spectral data. This corrects a previous interpretation by Cook et al.The endo → exo-aminal isomerization (4 → 6) is considered to occur via the enamine (5) of bicyclo[3.1.0]hex-2-ene-6-carbaldehyde (3 or 7), with which the aminals (4 and 6) are in equilibrium. The same enamine (5), a methylidene cyclopropane derivative, is thought to be the intermediate in the aminal (4 or 6) → amino-homofulvene (8 and 9) conversion, which, therefore, belongs to the vinyl-methylidene-cyclopropane rearrangement type.A cationic mechanism for the endo → exo-aminal isomerization is excluded by the discrepancy in this reaction of the pyrrolidino-aminals (13 and 15) of 6-exo-methyl-bicyclo[3.1.0]hex-2-ene-6-endo-carbaldehyde (12) and of bicyclo[3.1.0]hexane-6-endo-carbaldehyde (14). While the former aminal (13) is stable even under acid catalysis and at higher temperatures, the latter (15) isomerizes readily to the exo-aminal 16.The three endo-aldehydes 3, 12 and 14 were prepared by the alkali catalyzed rearrangement of the three chlorohydrins 7-endo-chloro-bicyclo[3.2.0]hept-2-en-6-endo-ol (20ac), 7-endo-chloro-7-exo-methyl-bicyclo[3.2.0]hept-2-en-6-endo-ol (20ad) and 7-endo-chloro-bicyclo[3.2.0]heptan-6-endo-ol (20bc) according to the method of Brook.The configurations of the unsaturated endo-aldehydes 3 and 12 followed from their equilibria with the corresponding 2-oxa-bicyclo[3.2.1]octa-3,6-diene systems (23) and those of the saturated aldehydes 14 and 17 from oxidations to the corresponding carboxylic acids. The endo- and exo- isomers of the aldehydes and aminals treated in this work were readily distinguished by certain highly characteristic NMR.-signals.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 57 (1974), S. 602-615 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Die Struktur des Sesquiterpen-γ-Laktons Arteannuin B (1) wurde röntgenographisch und diejenige seines Hydrolyseproduktes (2) durch eine vollständige Analyse des NMR.-Spektrums ermittelt.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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