From rotaxanes to knots. Templating, hydrogen bond patterns, and cyclochirality

Rotaxanes of the amide type have been accessible in preparative yields by a variety of reactions. Beneath S(N)2- and S(N)2(t)-mechanisms we developed a synthesis of [2]rotaxanes that comes off a Michael addition. The motif of the attractive interactions between an axle-shaped and a macrocyclic wheel part to form rotaxanes consists of multiple hydrogen bonds in the nonionic strategy (threading), as well as in a new high yield anionic template synt hesis (trapping). We introduce new synthetic routes for the preparation of [n]rotaxanes using nonionic as well as anionic templates. Furthermore, we r eport on the latest results of the statistical synthesis (slipping) by melt ing together axle and wheel to form rotaxanes. The chiroptical properties o f a homologous series of cycloenantiomeric [1]rotaxanes as well as a cyclod iastereomeric [3]rotaxane have been described. The differences in the Cotto n effects obtained show that small structural changes have an impact on the chiroptical properties of rotaxanes. The first X-ray structures obtained o f cycloenantiomerically chiral amide-based [2]- and [2]rotaxanes as well as of the first topologically chiral amide-based knot compound were solved wh ich show networks of H-bonds between the entities of the rotaxanes and the segments of the knot-shaped molecule. Our investigations in template effect s based on hydrogen bonding for the synthesis of supramolecular structures open up a variety of strategies for the preparation of catenanes, rotaxanes and-recently-even molecular knots.