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

Cationic diaza[4]helicenes are fluorescent scaffolds whose properties can be tuned by late-stage functionalization, although access to unsymmetrically substituted derivatives remains limited. Here, we report an acid-mediated skeletal rearrangement of 1,13-dimethoxyquinacridinium derivatives that enables sequential migration of methoxy groups and provides new 1,11- and 3,11-substituted cationic [4]helicene regioisomers. The rearranged compounds were obtained through reduction or methyl addition, Brønsted acid treatment, and aerobic photooxidation, and their structures supported by spectroscopic and crystallographic analyses. These core-edited dyes display progressive planarization, modified redox behavior, and marked hypsochromic shifts in absorption and emission relative to the parent scaffold. The mono-rearranged platform also undergoes selective peripheral editing by SNAr and demethylation/refunctionalization, giving access to a diverse family of O- and N-substituted derivatives with finely tuned photophysical properties. Importantly, the new helicenes are configurationally labile, with enantiomerization barriers around 19 kcal·mol⁻¹, in contrast to the configurationally stable parent system. This dynamic chirality enables asymmetric induction through covalently bound chiral auxiliaries and ion pairing with enantiopure TRISPHAT, leading to moderate diastereomeric enrichment and measurable ECD responses

Organizational unit

Laboratory of Professor Jérôme Lacour

Type

Dataset

DOI

10.26037/yareta:dthr7jssmrcndfkvk6bjc7t4ta

License

Creative Commons Attribution 4.0 International

Keywords

cationic diaza[4]helicenes, skeletal rearrangement, acid-mediated, quinacridinium dyes, late-stage functionalization, dynamic chirality, peripheral editing, nucleophilic aromatic substitution, photophysical properties, TRISPHAT