The lateral π-extension of helicenes would yield interesting physical properties derived from the enhanced π-stacking ability as well as intrinsic helical chirality. Here we report the regiodivergent synthesis of hexabenzocoronene (HBC)-based [6]helicenes via cationic rhodium(I)/segphos complex-mediated intramolecular [2 + 2 + 2] and [2 + 1 + 2 + 1] cycloadditions of triynes followed by Scholl reaction. The resulting HBC-based[6]helicenes possess stable helical chirality but more planar structure than previously reported HBC-based [7] and [9]helicenes. Therefore, these HBC-based [6]helicenes exhibit πstacking-induced chiral self-recognition in solution, allowing the measurement of enantiomeric ratios by 1 H NMR spectroscopy without any chiral additive.
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