Four-Fold Alkyne Benzannulation: Synthesis, Properties, and Structure of Pyreno[a]pyrene-Based Helicene Hybrids.

The synthesis of pyreno[a]pyrene-based helicene hybrids was achieved in good yield via a four-fold alkyne benzannulation reaction that was promoted by Brønsted acid. The molecules are configurationally locked, allowing the enantiomers to be separated using chiral HPLC so that their photophysical and chiroptical properties, including circular dichroism and circularly polarized luminescence, could be studied.