A Swell Stopper

See allHide authors and affiliations

Science  23 Mar 2007:
Vol. 315, Issue 5819, pp. 1639
DOI: 10.1126/science.315.5819.1639c

In rotaxane molecules, macrocycles are held onto rodlike cores by bulky end groups that effectively act as stoppers. Rotaxane synthesis usually requires first threading an open-ended rod through the cycle, followed by the addition of a third molecule to the free end of the rod in order to form the second stopper. Chiu et al. present a two-component system in which an enyl-2-vinylcyclopropane end group of the rodlike molecule “swells” after the macrocycle has been threaded. A Cope rearrangement that is slow at room temperature occurs after 2 days of heating at 50°C, creating a bulky cycloheptadiene capping group. Hydrogenation of the racemic product mixture yields a single saturated isomer for the rodlike molecule. The authors demonstrate the technique with two different macrocycles, confirming by nuclear magnetic resonance spectroscopy that the rods and rings successfully interlock. — PDS

J. Am. Chem. Soc. 129, 10.1021/ja069362i (2007).

Navigate This Article