Modular Synthesis of pH-Sensitive Fluorescent Diaza[4]helicenes

Article Article scientifique Article Modular Synthesis of pH-Sensitive Fluorescent Diaza[4]helicenes eng 2014 author Wallabregue Antoine 735776 author Sherin Petr 718687 author Guin Joyram 676787 author Besnard Céline 682138 author Vauthey Eric 0000-0002-9580-9683 133895 author Lacour Jérôme 0000-0001-6247-8059 99165 6431-6438 10.1002/ejoc.201402863 1099-0690 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). Fluorescence PH Sensing Helicenes Chiral resolution Reaction mechanisms Dewey 540 36 Département de chimie organique 141 38 Département de chimie physique 142 false European journal of organic chemistry 2014 29 64efd7a0-80f0-4a41-b755-e4c0a672bd3a Article (Published version) Restricted 6431_ftp.pdf 1099590 application/pdf restrictedAccess Faculté des sciences / Section de chimie et biochimie / Département de chimie organique Faculté des sciences / Section de chimie et biochimie / Département de chimie physique

Title	Published in	Year	Views	Downloads

Modular Synthesis of pH-Sensitive Fluorescent Diaza[4]helicenes	European journal of organic chemistry	2014	770	10
Highly selective additions of hydride and organolithium nucleophiles to helical carbenium ions	Chemical science	2011	602	14
Synthesis, resolution, and stabilities of a cationic chromenoxanthene [4]helicene	Organic letters	2010	760	0

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Guin, Joyram