Synthesis of Dithiahelicenes and Enantioselective Synthesis of Helically Chiral Thiahelicenes via Rh-Catalyzed Intramolecular [2 + 2 + 2] Cycloaddition of Triynes.J Org Chem. 2023 Jun 16; 88(12):7703-7711.JO
Dithiahelicenes and helically chiral thiahelicenes were synthesized in high yields via a cationic Rh-catalyzed intramolecular [2 + 2 + 2] cycloaddition of triynes bearing sulfur-containing 1,6-diynes. Thiahelicene could be obtained with a high enantiomeric excess of P-isomers by using (S)-SEGPHOS as a chiral ligand. This protocol is the first example of the synthesis of thiahelicenes via [2 + 2 + 2] cycloaddition and can also be used for the asymmetric construction of an azahelical skeleton.