Hayase Norihiko, Sugiyama Haruki, Uekusa Hidehiro, Shibata Yu, Tanaka Ken
Org Lett. 2019 Jun 7;21(11):3895-3899. doi: 10.1021/acs.orglett.9b00820. Epub 2019 Apr 11.
The synthesis of C-symmetrical [6]cycloparaphenylene (CPP) tetracarboxylates has been achieved via macrocyclization by the rhodium-catalyzed intermolecular stepwise cross-alkyne cyclotrimerization and subsequent reductive aromatization. The H NMR spectra of the thus-obtained C-symmetrical [6]CPP-tetracarboxylates revealed that the rotation of unsubstituted benzene rings is slow at room temperature. These [6]CPPs formed columnar packing structures, and their absorption maxima were significantly blue-shifted compared to that of nonsubstituted [6]CPP due to the presence of four electron-withdrawing ester moieties.
通过铑催化的分子间逐步交叉炔烃环三聚反应进行大环化，随后进行还原芳构化，实现了C对称的[6]环对亚苯基（CPP）四羧酸盐的合成。由此获得的C对称[6]CPP-四羧酸盐的1H NMR光谱表明，未取代苯环在室温下的旋转较慢。这些[6]CPP形成柱状堆积结构，由于存在四个吸电子酯基，它们的吸收最大值与未取代的[6]CPP相比有明显的蓝移。
