Chiral [1]rotaxanes: X-ray structures and chiroptical properties

New chiral [1]rotaxanes with aromatic bridges were prepared in yields up to 72% starting from a [2]rotaxane with sulfonamide groups in wheel and axle. The X-ray structures of the the parent [2]rotaxane I and of the three [1]r otaxanes 3e,g,h were solved which show networks of H-bonds between wheel an d axle. The separation of the racemic mixtures of four of the [1]rotaxanes, ie., of 3a,b,d,e, was possible with HPLC on Chiracel OD. The aromatic chro mophores in the bridges lead to a considerable enhancement of the intensiti es of the molar CD as compared to the analogues with aliphatic bridges In o ne case (3d), the Cotton effects am as strong as those usually found in hel icenes.