One‐Pot Oxidative Aromatization and Dearomatization of Tetrahydro[5]helicene Diols: Synthesis, Structure, Photophysical and Chiroptical Properties of Chiral π‐Extended Diones

Abstract One‐pot oxidative aromatization and dearomatization (OADA) reactions of tetrahydro[5]helicene diols with 2,3‐dichloro‐5,6‐dicyanobenzoquinone (DDQ) as the oxidant were demonstrated, which provided an efficient method for the synthesis of chiral π‐extended diones. Consequently, a series of enantiomeric π‐extended diones were obtained in high yields by a one‐pot OADA of dibromo‐substituted tetrahydro[5]helicene diols, and then followed by Suzuki‐Miyaura cross‐coupling reactions, or vice versa. The absolute configurations of the chiral diones were determined by their CD spectral analysis and X‐ray structure of the dibromo‐substituted dione. Moreover, the enantiomeric diones also exhibited mirror‐imaged CD spectra and showed mirror‐imaged circularly polarized luminescence (CPL) properties with the luminescence dissymmetry factor up to ±9.0×10 −4 . It was further found that the chiral diones showed different fluorescence spectra, and substituent‐dependent fluorescence quantum yields. For the chiral diones with strong electron‐donating groups, high fluorescence quantum yields of up to 30.3% were found. Such chiral diones with high fluorescence quantum yields and significant CPL properties might have potential applications not only in asymmetric catalytic synthesis, but also chiroptical materials.