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Triptycene-Based Ladder Polymers with One-Handed Helical Geometry

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posted on 28.02.2019, 00:00 by Tomoyuki Ikai, Takumu Yoshida, Ken-ichi Shinohara, Tsuyoshi Taniguchi, Yuya Wada, Timothy M. Swager
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.