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Scientific article
English

Surprisingly Difficult Resolution of N-Methylated Cationic [4]Helicenes

Published inChirality, vol. 24, no. 11, p. 928-935
Publication date2012
Abstract

1,13-Dimethoxyquinacridinium ions of type 3 are highly configurationally stable [4]helicenes that can be synthesized in racemic form in a single step from tris(2,6-dimethoxyphenyl)methylium ion. Previously, it had been shown that the single enantiomers can be routinely obtained from racemic mixtures through Pummerer fragmentations of diastereomerically pure sulfoxide adducts that release the enantiopure cations after a C–C bond rupture. This resolution protocol is readily performed because of a (normally) large retention difference of the diastereomers over silica gel. Herein, we report that it is not always the case. Introduction of N-methyl side chain(s) at the periphery of the helical quinacridinium cations, which are needed for photophysical and biological studies, has a large negative effect of this separation. Instead of simple, rapid, and multigram separations by flash chromatography, extensive semi-preparative high-performance liquid chromatography sequences are now required.

Keywords
  • Chromatography
  • Helicene
  • Resolution
  • Side chain effect
  • Sulfoxide
Citation (ISO format)
MEHANNA, Nathalie, GRASS, Stéphane, LACOUR, Jérôme. Surprisingly Difficult Resolution of N-Methylated Cationic [4]Helicenes. In: Chirality, 2012, vol. 24, n° 11, p. 928–935. doi: 10.1002/chir.22032
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Article (Published version)
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Identifiers
ISSN of the journal0899-0042
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Technical informations

Creation10/24/2012 1:26:00 PM
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