Rhodium‐Catalyzed Enantioselective Synthesis, Structures, and Properties of Single and Double Azahelicene‐Like Molecules

• Published in: Chemistry : a European journal 2021-06, Vol.27 (36), p.9313-9319
• Main Authors: Hanada, Kyoichi, Nogami, Juntaro, Miyamoto, Kazunori, Hayase, Norihiko, Nagashima, Yuki, Tanaka, Yusuke, Muranaka, Atsuya, Uchiyama, Masanobu, Tanaka, Ken
• Format: Article
• Language: English
• Subjects: [2+2+2] cycloaddition; asymmetric catalysis; azahelicene-like molecules; Chemical synthesis; Chemistry; circularly polarized luminescence; cyanodiynes; Cycloaddition; Enantiomers; Fluorescence; Racemization; Rhodium
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202005479

The enantioselective synthesis of aza[6] and [7]helicene‐like molecules have been achieved by the cationic rhodium(I)/axially chiral biaryl bisphosphine complex‐catalyzed intramolecular [2+2+2] cycloaddition of cyanodiynes. This protocol was successfully applied to the diastereo‐ and enantioselective synthesis of an S‐shaped double aza[6]helicene‐like molecule with a high ee value of 89 %. Although no epimerization and racemization were observed in the double carbo[6]helicene‐like molecule at 80 °C, epimerization and racemization of the double aza[6]helicene‐like molecule proceeded at 80 °C. This double aza[6]helicene‐like molecule showed good fluorescent quantum yields and chiroptical responses under both neutral and acidic conditions. The diastereo‐ and enantioselective synthesis of a configurationally stable S‐shaped double azahelicene‐like molecule showing good chiroptical responses has been achieved with the high ee value of 89 % by the rhodium(I)/xyl‐segphos‐complex‐catalyzed double [2+2+2] cycloaddition of a dicyanotetrayne.