Hashimoto S, Nakatsuka S, Nakamura M, * Hatakeyama T. * Kwansei Gakuin University, Hyogo, Kyoto University, and Japan Science and Technology Agency, Tokyo, Japan
Construction of a Highly Distorted Benzene Ring in a Double Helicene.
Angew. Chem. Int. Ed. 2014;
53: 14074-14076
Key words
aromaticity - helical structures - ligand design - Friedel–Crafts reaction
Significance
The authors report a new approach to construct distorted benzene rings by constraining a benzene ring between two opposing [5]helicenes. Double helicene 5 was synthesized via a tandem intramolecular phospha-Friedel–Crafts reaction. By X-ray crystallography, the central benzene ring of 5 was found to possess a bending angle of 23°, and the sulfur atoms were found to be in a cis arrangement.
Comment
Distorted double helicene 5 can be desulfurized with triethylphosphine to yield bis(phosphine) 7, which could find potential use as a C
2-symmetric ligand for bimetallic complexes, following separation of enantiomers.
