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Z. Naturforsch. 2014,
69b, 605 – 614
doi:10.5560/ZNB.2014-3324
Syntheses and Characterization of N-(Indolyl)pyridinium Salts and of Their Ylides
Clausthal University of Technology, Institute of Organic Chemistry, Leibnizstrasse 6, D-38678 Clausthal-Zellerfeld, Germany
Reprint requests to Prof. Dr. Andreas Schmidt. E-mail:
schmidt@ioc.tu-clausthal.de
Received December 11, 2013 / published online May 7, 2014
3-Methylindole reacts with pyridines in the presence of NBS to give indol-2-yl-pyridinium salts which were converted into their ylides by an anion exchange resin in its hydroxide form. Indol-3-amine was subjected to a nucleophilic ring transformation with pyrylium salts which resulted in the formation of indol-3-yl-pyridinium salts, the 2,4,6-trimethylpyridinium derivative of which proved to be unstable. The 2,4,6-triphenylpyridinium derivate was deprotonated to the corresponding ylide. The isomeric indol-2-yl and indol-3-yl derivatives are cycloimmonium ylides which are members of the compound class of heterocyclic mesomeric betaines (MB). By contrast, the ylide of indol-2-yl-pyrrolidinium is a cycloammonium ylide. It was prepared by reaction of 3-methylindole with pyrrolidine in the presence of NBS, followed by deprotonation.
Key words: Mesomeric Betaines, Ylides, Mesoions, Immonium Ylides, Ammonium Ylides