Catenanes, rotaxanes and pretzelanes - Template synthesis and chirality

Abstract

Catenanes and Rotaxanes of the amide-type have been obtained in remarkable yields via supramolecular template syntheses. The amide-based structures can be designed by appropriate choice of building units. The regioselective synthesis of stable [2]catenane isomers allowed to draw conclusions about their formation. Tetralactams of type 1 act as a host for guests containg amide-units (cf. key-lock intermediate 3). If the guest molecule is cyclisized a catenane is formed while reaction with voluminous stopper groups yield a rotaxane. Rotaxanes can also be synthesized by the 'slipping method' in which wheel and axle are heated at about 300 °C for minutes. The formation of rotaxanes containing aliphatic chain axles showed that π-π-interactions are not necessary. Introduction of a sulfonamide unit allowed us to do chemistry with catenanes and rotaxanes (cf. 14, 15) and furthermore to synthesize topologically chiral spieces (15). © 1999 IUPAC.