Rhodium‐Catalyzed Enantioselective Synthesis, Structures, and Properties of Single and Double Azahelicene‐Like Molecules
Kyoichi Hanada, Juntaro Nogami, Kazunori Miyamoto, Norihiko Hayase, Yuki Nagashima, Yusuke Tanaka, Atsuya Muranaka, Masanobu Uchiyama, Ken Tanaka
Abstract
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.