Triptycene-Based Ladder Polymers with One-Handed Helical Geometry

Here we report an efficient synthesis of optically active ladder-type molecules and polymers through intramolecular cyclization of chiral triptycenes containing bis[2-(4-alkoxyphenyl)ethynyl]phenylene units. The electrophile-induced cyclization reactions are directed away from the bridgehead carbon atoms of triptycene by steric factors, thereby producing one-handed twisted ladder units without any detectable byproducts. Moreover, the quantitative and regioselective nature of this intramolecular cyclization allowed us to synthesize optically active ladder polymers with a well-defined one-handed helical geometry in which homoconjugated dibenzo[a,h]anthracene units are helically arranged along the main chain. This synthesis route enables the construction of a variety of nanoscale helical ladder architectures and provides an entry into new chiroptical materials.