Triple Oxa[7]helicene with Circularly Polarized Luminescence: Enhancing the Dissymmetry Factors via Helicene Subunit Multiplication.

The development of multiple heterohelicenes with a high luminescence dissymmetry factor (glum) is an appealing yet challenging task. Herein, we disclose the synthesis of a structurally unusual furan-based triple oxa[7]helicene, which represents the first reported triple hetero[7]helicene, via [2+2+2] cyclotrimerization/intramolecular dehydrogenative annulation. Compared to the reported double oxa[7]helicene, the triple oxa[7]helicene exhibits an improved glum value of 1.8 × 10-3, exemplifying the potential of the helicene subunit multiplication approach to enhance the glum of heterohelicenes.