Inducing Axial Chirality in a "Geländer" Oligomer by Length Mismatch of the Oligomer Strands

Helical molecules are not only esthetically appealing due to their structural beauty, they also display unique physical properties as a result of their chirality. We describe herein a new approach to “Geländer” oligomers by interlinking two oligomer strands of different length. To compensate for the dimensional mismatch, the longer oligo(benzyl ether) oligomer wraps around the oligophenyl backbone. The new “Geländer” oligomer 1 was assembled in a sequence of functional-group transformations and cross-coupling steps followed by final cyclizations based on nucleophilic substitution reactions, and was fully characterized, including X-ray diffraction analysis. The isolation of pure enantiomers enabled the racemization process to be studied by circular dichroism spectroscopy.