Electrosynthetic access to unsymmetrical oxaza8helicenes with high chiral stability and strong circularly polarized luminescence (CPL)

Heterohelicenes are compelling chiral π-conjugated scaffolds for optoelectronic and chiral-photonic technologies because their helical frameworks and doped heteroatoms endow them with various photophysical, chiroptical, and electronic merits. However, unsymmetrical heterohelicenes remain rare, as their synthesis is often hindered by chemoselectivity and regioselective control. Here, we exploit the differential redox potentials of two coupling partners as a key player to achieve a chemo- and regioselective electrosynthetic access to a new family of unsymmetrical oxaza8helicenes. A controlled anodic sequence enables selective oxidative hetero-coupling followed by dehydrative cyclization, furnishing the extended 8helical scaffold efficiently under mild, oxidant-free conditions. Structural analyses show retained aromaticity, increased helical distortion, and higher configurational stability (≈38 kcal/mol) relative to their oxaza7helicene analogues (<25 kcal/mol). After chiral HPLC separation, the enantiomers display mirror-image CD and strong solution CPL, with | g lum | up to 2.6 × 10 −3 and fluorescence brightness up to 30.75 M −1 cm −1 .