Abstract
The regioselective acylation of 2-methylindole (2) with acyclic di- and trialkoxycarbenium tetrafluoroborates1 produces, by way of the stable indolyl-alkoxycarbenium ions4, the 3-acylated indoles5a–5c, and the 3-methoxy-carbonylindole5d. The ambident electrophilic cations1 all react as a1-electrophiles with the very nucleophilic indole2. In the reaction of2 with trimethoxycarbenium tetrafluoroborate (2d) methylated products are formed additionally.
Zusammenfassung
Die regioselektive Acylierung von 2-Methylindol (2) mit acyclischen Di- und Trialkoxycarbenium-tetrafluoroboraten1 liefert über die stabilen Indolyl-alkoxycarbenium-Ionen4 die 3-acylierten Indole5a–5c und das 3-Methoxycarbonylindol5d. Die ambidenten elektrophilen Kationen1 reagieren gegenüber dem gut nukleophilen Indol2 bevorzugt als a1-Elektrophil. In der Reaktion von2 mit dem Trimethoxycarbenium-tetrafluoroborat1d werden zusätzlich auch methylierte Produkte gebildet.
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Pindur, U., Flo, C. Regioselective, mild acylation of 2-methylindole with di- and trialkoxycarbenium tetrafluoroborates—A simple procedure for deriving 3-acyl-2-methyl-indoles and 3-methoxycarbonyl-2-methylindole. Monatsh Chem 117, 375–383 (1986). https://doi.org/10.1007/BF00816532
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DOI: https://doi.org/10.1007/BF00816532