Crown Ethers Stoddart

Stoddart and coworkers [112-115] cyclized bis(bipyridyl)s in the presence of crown ethers to obtain a [2]catenane at a yield of 70%. It is illustrated in Fig. 37. The high yield can be attributed to the 7i-donor-acceptor interaction between the ring and the axle. It was shown that one of the two intercrossed rings moves around the other. The group of Stoddart [116-118] reported [3-5] catenanes (see Fig. 38 for [3]catenane). The [5]catenane of Stoddart et al. [118] was named olympiadane , because it resembles the symbol logo of International Olympic Games, as seen in Fig. 39. 

M. C. T. Fyfe, J. F. Stoddart, (Supra)molecular Systems Based on Crown Ethers and Secondary Dialkylammonium Ions , Adv. Supramol Chem 1998, 5,1-53. 

The strong hydrogen bonding interactions observed between the oxygen atoms of crown ethers and the N-H groups of ammonium groups can be successfully employed to prepare pseudorotaxanes and rotaxanes by templated processes. This approach has been extensively utilised by Stoddart, Busch and others to obtain a wide range of interlocked species. 

One of the several ammonium-templated rotaxanes reported by Stoddart [56] is based on a threadlike ammonium species with terminal azido-groups (19). Upon mixing this axle with crown ether 20, the [2]pseudorotaxane 21 was formed (see Scheme 13). 

Attracted by the benefits of the cryptand effect, Coxon and Stoddart (1975, 1977) prepared the bicyclic compound [39]. Compared with the monocyclic crown ether [40], the bicyclic compound showed no increased ion binding... 

Chiral recognition of (f S)-a-phenylethylammonium and ( S)-phenylglycine methyl ester salts by crown ethers in which chiral carbohydrate structure elements are incorporated has been reported by Stoddart et al. (Curtis et al.,... 

E Weber, J Toner, F Vogtle, DA Laidler, JF Stoddart, RA Bartsch and CL Liotta, Crown Ether and Analogs, Wiley, Chichester, 1989. 

Fnchs, B. Nelson, A. Star, A. Stoddart, J. E Vidal, S. Amplification of dynamic chiral crown ether complexes dnring cyclic acetal formation. Angew. Chem. Int. Ed. 2003,42, 4220 224. 

The third chapter, by J. F. Stoddart, is concerned with a very hot subject, namely, the stereochemical aspects of crown ether chemistry. Many chapters have been written on this topic Stoddart s concentrates on the synthesis of a variety of chiral crown ethers and surveys some of their uses in different areas of physical, chemical, and biological science. 

Pseudopolyrotoxanes and polyrotoxanes are polymers composed of a linear polymer chain threaded through one or more cyclic species [Gihson and Mahan, 2000 Raymo and Stoddart, 1999]. Synthesis of pseudopolyrotoxanes and polyrotoxanes involves polymerization of monomer(s) in the presence of the cyclic species. Cyclodextrins, crown ethers, paraquots, and other macrocyclics are used as the cyclic component. Both step and chain polymerizations have heen successfully used. 

J. F. Stoddart and D. A. Laidler, in The Chemistry of Crown Ethers, Hydroxyl Groups and their Sulfur Analogues , part 1, ed. S. Patai, Wiley, New York, 1980, chap. 1. 

In the late 1980s, Stoddart and coworkers reported complexes between bisphenyl-ene crown ethers 24 (electron-rich, donors) and iV V -bipyridinium salts (electron-... 

The only reported example of this type of behavior comes from the work of Bal-zani and Stoddart and their teams. It is based upon the threading/unthreading processes of a pseudorotaxane (see Chapters 7 and 8),[701 with concomitant fluorescence output changes. The constituent components of the pseudorotaxane are a naphtho-crown ether, 25, and a diazapyrenium dication, 26. On accommodation of the diaza-pyrenium thread, a nonfluorescent complex is formed, abolishing the fluorescent properties of the individual components. This corresponds to the first row of the truth table as no inputs are present and no fluorescence output is observed. The introduction of protons (in the form of CF3S03H) causes an unthreading of the... 

Complexes formed between secondary dialkylammonium ions and crown ethers having fewer than 24 atoms in their macrocycles have been observed to occur in a face-to-face manner. See a. Metcalfe, J.C., Stoddart, J.F. and Jones, G. (1977) Journal of the American Chemical Society,... 

In the early 1980s, Stoddart and coworkers investigated the complexation of pyr-idinium dications (e.g., paraquat) using crown ethers [12]. The complexation of... 

Stoddart and coworkers have used imine condensation in two different contexts to form interlocked molecules. The authors have modified the crown ether component of their dialkylammonium / D B24C8 system to incorporate reversible imine subunits which allow for dynamic clipping around dialkylammonium cation 91 [60], Three diformyl spacers (92-94) have been investigated with the same acyclic diamine 95 for their thermodynamic stability and kinetics of macrocyclization (96). However, reduction with BH3 to the kinetically trapped macrocyclic secondary diamine has only been reported for reaction of the 2,6-diformylpyridine derivative (Scheme 10.19 97) [60a]. 

Gokel GW (1991) Crown ethers and cryptand In Stoddart JF (ed) Monographs in supramolecular chemistry, The Royal Society of Chemistry, Cambridge, UK... 

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