Naphthalene- and Anthracene-Based Aromatic Foldamers with Iminodicarbonyl Linkers: Their Stabilities and Application to a Chiral Photochromic System Using Retro [4 + 4] Cycloaddition

A circular dichroism (CD) spectral study on chiral aromatic chain imides possessing anthracene and
naphthalene moieties with bulky N substituents showed that their helical chirality based on folding remained
for a reasonably long time without racemization in solution. Racemization due to conformational
equilibration occurred very slowly, requiring over 1 week at ambient temperature. Their CD spectra both
in solution and in the solid state gave similar CD signals, suggesting retention of helicity observed in the
solid state even after dissolving. As an application of this novel chiral folding of aromatic chain imides,
a chiral photochromic system was investigated based on the photo [4 + 4] cycloaddition and its thermal
cycloreversion of an anthracene−naphthalene system. The foldamer possessing an anthracene moiety in
the center connected with two naphthalene moieties below and above it by iminodicarbonyl linkers was
prepared for this purpose. Induced CD was observed for the foldamer with (S)-1-(1-naphthyl)ethyl
substituents at the imide nitrogen atoms. Chiral photochromic cycles were monitored by CD spectral
measurement.