Construction of a highly distorted benzene ring in a double helicene

Abstract

A P-fused double helicene consisting of a highly distorted benzene ring, with a bending angle of 23°, has been synthesized by a tandem intramolecular phospha-Friedel-Crafts reaction. Despite the distortion and reduced aromaticity, the double helicene shows thermal and chemical stability. These are important features that make these compounds attractive for applications as a new C2-symmetric bisphosphine ligand. The simple strategy proposed in this work can be used to prepare a diverse range of distorted molecules.

Keywords: aromaticity; density functional calculations; helical structures; ligand design; structure elucidation.