Catenanes stereochemistry

For a discussion of the stereochemistry of these compounds, see Schill, G. Catenanes, Rotaxanes, and Knots, Academic Press NY, 1971, p. 11. 

Our definitions of the stereoisomeric center, line, and plane all stipulate the existence of bonds between the ligating element and its ligands. The exclusive use of these elements limits our analysis to classical stereochemistry and thus does not encompass the so-called topological isomerism (47) of interlocked rings—catenanes (48)—or of knots. As there is no bond between the rings of the catenanes we cannot expect to handle such compounds with a system based on connectedness. At the present stage of development, this limitation in scope... 

A. Topological Stereochemistry Catenanes and Knots, the Topological Link... 

So far we discussed the application of the graph theory in studies of electronic structure of molecules. In this chapter we shall describe some topological concepts that appeared in stereochemistry in connection with the investigations of a new remarkable type of chemical compounds, catenanes, rotaxanes, knots. 

The catenanes and related interlinked compounds have attracted considerable interest, not only because of the stereochemistry, but as important building units for the synthesis of large molecular assemblies. 

Frisch, H.L. and Wasserman, E. (1961) Chemical topology, J. Am. Chem. Soc. 83, 3789-3794. Schill, G. (1971) Catenanes, rotaxanes and knots. Academic Press, New York. Walba, D.M. (1985) Topological stereochemistry. Tetrahedron 41, 3161-3212. Dietrich-Buchecker, C.O. and Sauvage, J.P. (1987) Interlocking of molecular threads From the statistical approach to the templated synthesis of catenands, Chem. Rev. 87, 795-810. Philp, D. and Stoddart, J.F. (1991) Self-assembly in organic synthesis, Synlett 445-458. 

The excitement that chemists feel for the area of stereochemistry has hopefully rubbed off during your reading of this chapter. From simple enantiomers and diastereomers, to rotax-anes, catenanes, and knots, stereochemistry continues to challenge organic chemists to create molecules of increasing complexity, which inevitably leads to molecules with intriguing properties and simple aesthetic beauty. 

Mechanically interlocked molecules (MIMs), such as catenanes and rotaxanes, are molecules with at least two components that are not covalently bound, but interlocked in such a manner that they cannot be separated without the breaking of a covalent bond. Since this physical linkage is known as a mechanical bond [24], we refer to the stereochemistry of MIMs as mechanostereochemistry [25]. MIMs have been appreciated for their synthetic challenge and aesthetic value [26] as well as their potential applications. In particular, MIMs have garnered much interest as artificial molecular switches and machines [27-31] because their internal noncovalent bonding interactions can be modulated by external stimuli to control the relative translational and/or circumrotational motions of their interlocked... 

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