Abstract
<jats:p>We report an unexpected route to an oxo[4]helicene fluorescent dye scaffold via nucleophilic fluoride displacement, identified unintentionally during an attempted synthesis of a rosamine dye from pentafluorobenzaldehyde and an N,Ndialkyl-3-aminophenol. Structural assignment is supported by high-resolution mass spectrometry (parent dye Hel-Me: HRMS (ESI-TOF) m/z 411.125 for the molecular cation, calcd for C23H18F3N2O2+: 411.125) and multinuclear NMR spectroscopy (1H, 13C, 19F) of four independently synthesized dyes in this series (Hel-Me, Hel-Q, Hel-Jul, Hel-TOM), each showing a fluorine substitution pattern and mass inconsistent with the corresponding rosamine target but consistent with cyclization to a dioxo-fused helicene arising from intramolecular displacement of fluorine by the phenolic hydroxyl group. This scaffold is accessible in two to three steps from inexpensive, commercially available starting materials. A full account of the synthesis, scope, photophysical and electrochemical characterization of this dye series is in preparation and will be posted as a revised version of this preprint.</jats:p>