Total conversion of racemic [5]thiaheterohelicene into a single enantiomer by a diastereoisomeric charge-transfer complex formation

Racemic thieno[3,2-e:4,5-e′]di[1]benzothiophene was totally converted into a single enantiomer on crystallizing the charge-transfer complex with (S)-2-(2,4,5,7-tetranitro-9-fluorenylidene-amino-oxy)propionic acid; the structure of the complex was determined by X-ray crystallographic analysis.