A three-dimensional π-conjugated chiral cage with six [5]helicene units (a triple helicene cage) was synthesized for the first time. Taking advantage of the Yamamoto coupling reaction, the triflate-substituted triple [5]helicene, a strained and preorganized precursor, was dimerized to afford the target compound. Single-crystal X-ray diffraction analysis revealed the unique structural features of the triple helicene cage: a cage-shaped rigid structure with outer helical grooves and an inner chiral cavity. All-P and all-M enantiomers were separated successfully by HPLC over a chiral column and their chiroptical properties were characterized by circular dichroism spectra.
Keywords: aromaticity; chirality; multiple helicene; polycyclic aromatic hydrocarbons; π-conjugated cages.