2017 年 75 巻 5 号 p. 458-465
The enantioselective synthesis of helicenes have been achieved via the rhodium-catalyzed [2+2+2] cycloaddition. The rhodium-catalyzed enantioselective intramolecular [2+2+2] cycloaddition of 2-naphthol-linked triynes afforded helicenes with good yields and ee values. The rhodium-catalyzed enantioselective double intramolecular [2+2+2] cycloaddition of a 2-naphthol-linked hexayne also proceeded to give a helicene-like molecule with high ee value, although the product yield was low. Not only the intramolecular reactions but also intermolecular ones were accomplished by combination of electron-rich tetraynes and electron-poor diynes to give - and helicenes, and heterohelicenes in varying yields and ee values. Fluorescence quantum yields of thus synthesized helicenes were higher than unfunctionalized carbohelicenes and some of them exhibited excellent circular polarized luminescence (CPL) activity.