Synthesis of a Configurationally Locked [5]Helicene Derivative

The photochemical cyclisation-dehydrogenation of the bis-styrylbenzene 3, where the terminal aryl moieties are connected by a suitable chiral tether derived from 1,3-pentanediol, led to a chiral, configurationally locked [5]helicene derivative. An X-ray diffraction study showed that an (S,S)-configuration of the chiral auxiliary induces a (P)-configuration of the helical framework.