Synlett 2002(11): 1743-1761  
DOI: 10.1055/s-2002-34860
ACCOUNT
© Georg Thieme Verlag Stuttgart ˙ New York

From Kinetic to Thermodynamic Assembly of Catenanes: Error Checking, Supramolecular Protection and Oligocatenanes

Laurence Raehma, Darren G. Hamilton*b, Jeremy K. M. Sanders*a
University Chemical Laboratory, Lensfield Road, Cambridge, CB2 1EW, UK
e-Mail: jkms@cam.ac.uk;
Department of Chemistry, Mount Holyoke College, South Hadley, Massachusetts 01075, USA
e-Mail: hamilton@mtholyoke.edu;
Further Information

Publication History

Received 7 January 2002
Publication Date:
21 October 2002 (online)

Abstract

Catenanes are molecules comprising at least two mechanically interlocked rings: they cannot be separated, yet do not possess covalent links between ring constituents. Over the last two decades several efficient templating mechanisms for the assembly of catenanes, and other topologically complex molecules, have been developed and exploited in the synthesis of numerous systems, often with impressive efficiency. Kinetically controlled assembly routes, employing transition metal complexation or amide hydrogen bonding interactions, have proved tremendously successful. A third arena of investigation, and perhaps the most thoroughly explored and exploited, is the utilisation of π-complementary components, principally bipyridinium dications and aromatic ethers. In our work electron deficient bipyridinium dications were replaced with uncharged, yet electron accepting, aromatic diimides. This replacement permitted the use of a variety of ring closing reactions for catenane formation by allowing us to step away from the structurally powerful but ultimately limited chemistry demanded by bipyridinium systems. A total of four ring-closing reactions were employed: acetylenic coupling, Mitsunobu alkylation, Grubbs’ alkene metathesis, and zinc(II)-bipyridyl ligation. The first three methods yielded fully covalent interlocked systems, the fourth a catenane containing a metallomacrocycle. The first two methods employed irreversible bond forming reactions in catenane formation, the latter two thermodynamically controlled processes.

This flexible system of interacting components, the synthetic chemistry used in their preparation, and the structural flexibility offered by the combination of these factors, is discussed in terms of a series of model systems leading to the proposition of a method for the synthesis of a polycatenane. Such systems, polymeric chains of interlocked rings, are unrealised yet coveted goals of chemists working in the area of supramolecular topology and are predicted to exhibit valuable and unusual material properties.