Skeletal rearrangement of [4]helicenes under acid conditions; dynamic chirality and improved properties by subsequent peripheral editing

Article Article scientifique Article Skeletal rearrangement of [4]helicenes under acid conditions; dynamic chirality and improved properties by subsequent peripheral editing eng 2026 2026-05-13 author Gaucherand Arthur 418868 Chimie organique groupe 7 (CHOR7) author Duwald Romain 833167 author Herse Christelle 133298 author Besnard Céline 682138 Administration de la section de chimie (CHIAD) author Pescitelli Gennaro author Lacour Jérôme 0000-0001-6247-8059 99165 Département de chimie organique (CHIOR) 10422-10433 10.1039/D6SC03190K 2041-6520 http://pubs.rsc.org/en/Content/ArticleLanding/2026/SC/D6SC03190K Cationic diaza[4]helicenes are attractive fluorescent scaffolds, yet access to unsymmetrical substitution patterns remains limited. Here, we report that chiral 1,13-dimethoxyquinacridinium (DMQA) derivatives undergo an acid-mediated skeletal rearrangement after hydride or methyl addition, enabling the sequential migration of methoxy groups and providing unprecedented 1,11- and 3,11-substituted cationic [4]helicene regioisomers. Following aerobic photooxidation, the rearranged helicenes were isolated and characterized by spectroscopy, electrochemistry, crystallography, and computation. Relative to the parent 1,13-DMQA scaffold, these core-edited systems display progressive planarization, altered redox behavior, and marked hypsochromic shifts in both absorption and emission, together with improved fluorescence efficiencies. The mono-rearranged platform further enables selective peripheral editing through S<sub><i>N</i></sub>Ar substitution and regioselective demethylation/refunctionalization, giving access to a broad family of O- and N-substituted dyes with finely tunable optical properties. Importantly, relocation of one methoxy group away from the helical groove lowers strongly the configurational barrier, affording configurationally-labile helicenes with enantiomerization barriers of about 19 kcal·mol⁻¹. This dynamic chirality allows asymmetric induction studies through covalently bound chiral appendages and ion pairing with enantiopure TRISPHAT anion, leading to moderate diastereomeric enrichment and measurable ECD responses Dewey 540 Swiss National Science Foundation Superstable Chiral Cations and Reactive Ylides for Synthesis, Catalysis and Optical Applications 207539 CH Swiss National Science Foundation Superstable Cations and Reactive ylides for Synthesis, Catalysis and (Bio)Optical Applications 184843 CH 36 Département de chimie organique 141 false 760 Groupe Lacour https://doi.org/10.26037/yareta:dthr7jssmrcndfkvk6bjc7t4ta Chemical science 2026 17 38434a5d-2ca8-4444-af16-6e0e59dbeaca Article (Published version) Public ChemSci_2026_Rearranged_DMQAs_LSF_w.pdf 2310672 application/pdf CC BY-4.0 900ff697d1b034d0c0793d441367952ee6951b0f868d991ba638d1c9d6566f43 Vignette Public TOC.jpg 103705 image/png openAccess Faculté des sciences / Section de chimie et biochimie / Département de chimie organique

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Skeletal rearrangement of [4]helicenes under acid conditions; dynamic chirality and improved properties by subsequent peripheral editing	Chemical science			2026	67	38

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