Synthesis of magic ring catenanes by olefin metathesis

ORGN 739

Erin N. Guidry, eguidry@caltech.edu1, Stuart J. Cantrill, cantrill@chem.ucla.edu2, and Robert H. Grubbs, rhg@caltech.edu1. (1) Arnold and Mabel Beckman Laboratory of Chemical Synthesis, Division of Chemistry and Chemical Engineering, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, (2) Department of Chemistry and Biochemistry, California NanoSystems Institute, University of California, Los Angeles, 405 Hilgard Avenue, Los Angeles, CA 90095-1569
Interlocked molecules such as catenanes and rotaxanes have long been of interest to chemists as a consequence of their unique constructions and novel molecular topologies. Furthermore, recent advances in materials science and molecular computation have shown that these molecules are not only aesthetically pleasing, but may constitute useful raw materials in these fields. Numerous examples of catenane and rotaxane syntheses have appeared in the chemical literature, but most of these methods employ a final kinetically controlled covalent bond forming step. This strategy often results in the irreversible formation of unwanted non-interlocked side products. One potential solution to this problem is the use of reversible reactions, which are under thermodynamic control, as the final reaction step. Recently, however, it has been shown in the Grubbs' group that the ring closing of certain diolefinic polyether substrates around appropriately substituted secondary dialkyl-ammonium ions results in the reversible formation (i.e., under thermodynamic control) of [2]rotaxanes. Here, it is shown that this convenient, high yielding method for creating rotaxanes can be extended to the creation of [2]catenanes templated by polyether / ammonium ion recognition.