Synthesis for the Mesomer and Racemate of Thiophene-Based Double Helicene under Irradiation

In this work, the racemate and mesomer
of the thiophene-based naphthalene-cored
double helicenes (1) were obtained efficiently by one-pot
photocyclization of 1,1,2,2-tetrakis­(dithieno­[2,3-b:3′,2′-d]­thiophen-2-yl)­ethene in the
presence of iodine in dry benzene. The structure of meso-1a was confirmed by single crystal X-ray analysis.
The chiral resolution of the racemate was carried out by chiral HPLC,
and the chiral properties, such as CD spectra, optical rotations,
and half-life of enantiomers were characterized.