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Limited access to UNIGEOther version: http://doi.wiley.com/10.1002/ejoc.201402863
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unige:40860 
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Modular Synthesis of pH-Sensitive Fluorescent Diaza[4]helicenes |
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| Published in | European Journal of Organic Chemistry. 2014, vol. 2014, no. 29, p. 6431-6438 | |
| Abstract | Configurationally stable diaza[4]helicenes have been prepared in two steps by using a particularly facile N–N bond-cleavage reaction. The synthetic procedure uses hydrazine (NH2NH2) for the introduction of a single nitrogen atom. The strategy is general, modular and highly tolerant to functional groups. A mechanistic rationale is proposed for the spontaneous N–N bond-cleavage reaction. The resulting helical quinacridines are dyes that present absorption and emission properties that can be modulated as a function of pH; the pink quinacridine and green protonated forms (pKa ≈ 9.0) display distinct optical features in the near-IR region. Single enantiomers were obtained by chiral stationary phase HPLC resolution. The absolute configurations were assigned by comparison of the ECD spectra of the conjugated acids with those of known dialkylquinacridinium derivatives. A rather high racemization barrier was measured by means of variable-temperature ECD experiments (ΔG‡ = 30.7 ± 4.0 kcal mol–1 at 140 °C). | |
| Keywords | Fluorescence — PH Sensing — Helicenes — Chiral resolution — Reaction mechanisms | |
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Article (Published version) (1 MB) - Limited access to UNIGE Other version: http://doi.wiley.com/10.1002/ejoc.201402863 |
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| Citation (ISO format) | WALLABREGUE, Antoine et al. Modular Synthesis of pH-Sensitive Fluorescent Diaza[4]helicenes. In: European Journal of Organic Chemistry, 2014, vol. 2014, n° 29, p. 6431-6438. https://archive-ouverte.unige.ch/unige:40860 |
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