ORGN 685 |
| The molecular construction of the Borromean Ring (BR) topology has long been a formidable synthetic challenge as they consist of three noncatenated, yet mutually interlocked rings. The complete molecular construction of the BR topology has been achieved1-2 successfully from 18 individual components under strict dynamic covalent, coordinative and supramolecular control. So strict, that a subtle change in reaction conditions has been shown to favor other species, including a molecular Solomon knot.3 Varying the structure of these components has demonstrated that the molecular BR topology can provide a unique symmetrical, nanoscale three-dimensional scaffold into which various structural features can be imbedded at will.4–7 The dynamic construction of the BR topology is predicated on the ability to control the placement of 12 organic ligands around 6 transition metals. Stabilized by combinations of 12 π–π stacking interactions and 30 dative bonds, six tridentate and six bidentate ligands are spatially preorganized around six transition metals, such that they preferentially react and form molecular Borromean Rings in a single step in yields of greater than 95%. When the cooperativity of the system is eliminated by breaking down the BR components into analogous subunits, a solvent-dependent dynamic mixture of multiple products is realized (Box) in which there is no single preference for the metal-ligand coordination geometry, fully demonstrating the power of cooperativity in the dynamic covalent synthesis of the BR topology. (1) Science 2004, 304, 1308–1312. (2)Acc. Chem. Res. 2005, 38, 1–9. (3) Angew. Chem. Int. Ed. 2007, 46, In Press. (4) J. Org. Chem. 2005, 70, 7956–7962. (5) Chem. Commun. 2005, 3391–3393 (6) Chem. Commun. 2005, 3394–3396. (7) Angew. Chem. Int. Ed. 2006, 45, 409-4104.
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Asymmetric Reactions, Combinatorial Chemistry, Molecular Recognition and Self-Assembly, Proteins, Peptides, Amino Acids and Enzyme Inhibitors
8:00 PM-10:00 PM, Wednesday, March 28, 2007 Hyatt Regency Chicago -- Riverside Center, Poster
Division of Organic Chemistry |
