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  • 1
    ISSN: 1434-4475
    Keywords: Alkoxyalkylation of (trimethylsilyl) keten acetals, with ZnCl2·Et2O as Lewis-acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung O-Methyl-O-(trimethylsilyl)keten-acetale wurden mit 2-Alkoxy-1,3-dioxolanen1 in Gegenwart von Zinkdichlorid regioselektiv alkoxyalkyliert. Dieses Verfahren stellt einen guten Weg zur Gewinnung von α-geschützten β-Ketokarbonsäureestern4 dar.
    Notes: Abstract O-Methyl-O-(trimethylsilyl) keten acetals2 were regioselectively alkoxyalkylated by 2-alkoxy-1,3-dioxolanes1 in the presence of zinc chloride. This method represents a good way for synthesis of α-protected β-keto carbonic esters4.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 112 (1979), S. 2436-2443 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reaction of α-Halogen Sulfides with Antimony PentachlorideContrary to reports in the literature 5-7), the carbenium salts 2 and 3 are not obtained from antimony pentachloride and chloromethyl methyl sulfide or dichloromethyl methyl sulfide; instead, the reaction leads to the chlorosulfonium salts 8 and 11. On the other hand trichloromethyl methyl sulfide is indeed converted into the carbenium salt 4 by treatment with antimony pentachloride 7). The structures of 8, 11, and 4 are confirmed by analytical and spectroscopic data as well as by the reaction of the isolated compounds with dimethyl sulfide and triphenylphosphane. The carbenium ion 3 may be generated in solution around - 30°C and characterized as a mixture of E/Z isomers by 13C NMR spectroscopy.
    Notes: Die Reaktion von Antimonpentachlorid mit (Chlormethyl)methylsulfid und (Dichlormethyl)-methylsulfid führt entgegen den Literaturangaben5-7) nicht zu den Carbeniumsalzen 2 und 3, sondern zu den Chlorsulfoniumsalzen 8 und 11. Die analoge Umsetzung von Antimonpentachlorid mit (Trichlormethyl)methylsulfid liefert hingegen das Carbeniumsalz 47). Reaktionen mit Dimethylsulfid und Triphenylphosphan stützen die analytisch und spektroskopisch abgeleiteten Konstitutionen von 8,11 und 4. Das Carbenium-Ion 3 läßt sich in Lösung bei etwa - 30°C erzeugen und im 13C-NMR-Spektrum als Gemisch von E/Z-Isomeren charakterisieren.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Functionalizations with Silyl Enol Ethers, V. - Zinc Chloride-mediated Alkoxyalkylation of Trimethylsilyl Enol Ethers with 2-Alkoxy-1,3-dioxanes to α-Dioxanyl KetonesThe synthetic potential of Lewis acid-mediated alkoxyalkylation of silyl enol ethers with some SN1-active 2-alkoxy-1,3-dioxanes 1, 2 for the preparation of α-dioxanyl ketones 6 is described.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of Electron-rich Heterocycles with Orthocarboxylic Acid Derivatives, 9. - Acylation of Indole and Methylindoles with Dialkoxycarbenium TetrafluoroboratesIndole and some methylindoles 1 were acylated regioselectively with dialkoxycarbenium tetrafluoroborates 2 under mild conditions. The formyl cation equivalent 2a′ reacts with excess of indoles 1 to give the bisindolylcarbenium tetrafluoroborates 13a - d.
    Notes: Indol und einige Methylderivate 1 lassen sich unter milden Bedingungen mit den Dialkoxycarbenium-tetrafluoroboraten 2 in meist guten Ausbeuten regioselektive acylieren. Mit dem Formylkation-Äquivalent 2a′ werden mit überschüssigem 1 auch die Bisindolycarbenium-tetrafluoroborate 13a - d erhalten.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1981 (1981), S. 47-51 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Stabilization of Thioniumcarbenium Salts by + M SubstituentsIn order to stabilize thioniumcarbenium salts apart from the methylthio group further substituents with a + M effect such as chlorine or phenyl are needed. The (methylthio)phenylmethylium hexachloroantimonate (8) and the (methylthio)diphenylmethylium hexachloroantimonate (12) are described as an illustration for this. Reaction of chloromethyl methyl sulfide (4a) with aluminium or boron trichloride yields only the sulfonium salts 5, with boron tribromide the betain 6a is obtained.
    Notes: Zur Stabilisierung von Thioniumcarbenium-Salzen sind außer der Methylthiogruppe weitere Substituenten mit einem + M-Effekt wie Chlor oder Phenyl erforderlich. Als Beispiele hierfür werden das (Methylthio)phenylmethylium-hexachloroantimonat (8) und das (Methylthio)diphenylmethylium-hexachloroantimonat (12) beschrieben. Die Umsetzung von (Chlormethyl)methylsulfid (4a) mit Aluminium- oder Bortrichlorid liefert lediglich die Sulfoniumsalze 5, mit Bortribromid das Betain 6a.
    Additional Material: 1 Tab.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Liebigs Annalen 1986 (1986), S. 1628-1631 
    ISSN: 0170-2041
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Reaction of Indoles with 1,3-Dithiolenium Ions: a Simple Access to 3-(1,3-Dithiolan-2-yl)indoles3-Unsubstituted indoles 1 react regioselectively with 2-methyl- and 2-phenyl-1,3-dithiolenium ions 2 under mild conditions to give the 3-(1,3-dithiolan-2-yl)indoles 4 as protected 3-acylindoles.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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