Triptycene-Based Ladder Polymers with One-Handed Helical Geometry

J Am Chem Soc. 2019 Mar 20;141(11):4696-4703. doi: 10.1021/jacs.8b13865. Epub 2019 Mar 11.

Abstract

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.