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  • 1980-1984  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Reaktionen der Cyclopropene, IV. Cyclooligomerisierung des 3,3-Dimethylcyclopropens an Palladium(0)-Katalysatoren (1980)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 113 (1980), S. 2372-2382 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of Cyclopropenes, IV. Cyclooligomerisation of 3,3-Dimethylcyclopropene with Palladium(0) CatalystsThe cyclooligomerisation of 3,3-dimethylcyclopropene (1) with phosphane-free palladium(0) catalysts, e.g. bis(1,5-cyclooctadiene)palladium, bis(dibenzylideneacetone)palladium, or a catalyst prepared “in situ” from palladium acetylacetonate and ethoxydiethylaluminium, leads to the trans-tricyclohexane derivative 2 and to three isomeric tetrakishomocyclooctatetraene compounds (4) [4a (anti,syn,anti); 4b (anti,anti,anti); 4c (possibly syn,anti,anti)]. In contrast, a (tri-sec-alkylphosphane)palladium(0) catalyst (Pd/P = 1:1) cyclotrimerises 1 in aromatic hydrocarbons to give the trans-σ-trishomobenzene derivative 3 in over 90% yield. The cyclooligomerisation of 1 using other triorgano-phosphane or -phosphite/palladium(0) catalysts leads to a mixture of products. Besides 2, 3, and 4 a second cyclotrimer of 1 (5) and higher oligomers of 1 are produced. The cyclotrimerisation of 1 to 3 is also influenced by the Pd/phosphane ratio and the solvent used.
    Notes: 3,3-Dimethylcyclopropen (1) wird an phosphan-freien Palladium(0)-Katalysatoren, wie Bis(1,5-cyclooctadien)palladium, Bis(dibenzylidenaceton)palladium oder einem „in situ“ aus Palladiumacetylacetonat und Ethoxydiethylaluminium hergestellten Katalysator, zum trans-Tricyclohexanderivat 2 und zu drei isomeren Tetrakishomocyclooctatetraenen (4) [4a (anti,syn,anti); 4b (anti,anti,anti); 4c (vermutlich syn,anti,anti)] cyclisiert. Dagegen erfolgt an tri-sec-alkylphosphan-modifizierten Palladium(0)-Katalysatoren (Pd/P = 1:1) in aromatischen Kohlenwasserstoffen glatt eine Cyclotrimerisierung von 1 zum trans-σ-Trishomobenzolderivat 3. Andere Triorganylphosphan oder -phosphit/Palladium(0)-Katalysatoren bewirken eine uneinheitlichere Cyclooligomerisierung von 1. Neben 2, 3 und 4 entstehen auch 5 als weiteres Cyclotrimeres von 1 und höhere Oligomere. Auch das Palladium/Phosphan-Verhältnis sowie das Lösungsmittel können die Cyclotrimerisierung von 1 zu 3 beeinflussen.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19801130706
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  • 2
    Electronic Resource
    Electronic Resource
    Reaktionen der Cyclopropene, VI. Nickel(0)-katalysierte [2 + 1]-Cycloadditionen von 3,3-Diorganylcyclopropenen mit elektronenarmen Olefinen (1984)
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 117 (1984), S. 1551-1560 
    Details
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of Cyclopropenes, VI. Nickel(0) Catalyzed [2 + 1]-Cycloadditions of 3,3-Diorganocyclopropenes with Electron-deficient Olefins[2 + 1]-Cycloadditions of 3,3-diorganocyclopropenes [3,3-dimethyl- (1a), 3-methyl-3-phenyl-(1b), 3,3-diphenylcyclopropene (1c)] with electron-deficient olefins, e. g. methyl acrylate, methyl crotonate, dialkyl fumarate, and dialkyl maleate, to give the (2,2-diorganylvinyl)cyclopropanes 3 and 6 - 8 are catalyzed by phosphane-free nickel(0) compounds. In the cycloadducts the configuration of the olefins is mainly retained; with dialkyl maleates also the cycloaddition to 7a, c is stereoselective whereas with methyl acrylate a mixture of the cis/trans is formed.
    Notes: Phosphanfreie Nickel(0)-Verbindungen katalysieren die [2 + 1]-Cycloaddition von 3,3-Diorganyl-cyclopropenen [3,3-Dimethyl- (1a), 3-Methyl-3-phenyl- (1b), 3,3-Diphenylcyclopropen (1c)] mit elektronenarmen Olefinen, wie Methylacrylat, Methylcrotonat, Dialkylfumaraten und Dialkylmaleaten zu den (2,2-Diorganylvinyl)cyclopropanen 3 und 6 - 8, wobei die Konfiguration der Olefine weitgehend erhalten bleiben. Mit Maleaten verläuft auch die Cycloaddition stereoselektiv zu 7a, c, während mit Methylacrylat ein cis/trans-Gemisch von 3a - c entsteht.
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cber.19841170423
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