Cryptophanes synthesis

Cryptophane synthesis is accomplished by one of two methods. Initial procedures employed a covalent template effect in which one CTV-derived bowl preorganised the cyclisation of the second under high dilution conditions (Scheme 6.16a). More recently, a much more straightforward procedure has been developed in which cryptophanes are formed directly in a double trimerisation reaction (Scheme 6.16b). 

Scheme 6.16 Strategies for cryptophane synthesis. (Reproduced with permission from Section Key Reference).

An example of cryptophane synthesis using 5 as a template is depicted in Fig. 5. The cyclization precursor 37 was obtained by alkylation of 5 with iodide 36 in warm formic acid solution (high dilution 10 4 M), it was smoothly converted to a mixture of two cryptophane isomers in 77% overall yield [25]. The minor (27%)... 

Scheme 7.3), a useful intermediate on the way to cryptophane synthesis. The facile formation of the cyclic trimer (as opposed to polymers and higher oligomers) is an interesting aspect of this chemistry, and it is not known whether this is a result of thermodynamic equilibration (possibly driven by insolubility of the product), or the result of a kinetic template effect. 

The direct method of cryptophane synthesis involves simultaneous formation of both CTV fragments from a... 

Collet, A., Dutasta, J.-P., Lozach, B., and Canceill, J. Cyclotriveratrylenes and Cryptophanes Their Synthesis and Applications to Host-Guest Chemistry and to the Design of New Materials. 165, 103-129 (1993). 

Cyclotriveratrylenes and Cryptophanes Their Synthesis and Applications to Host-Guest Chemistry and to the Design of New Materials... 

Roesky, C. E. 0., Weber, E., Rambusch, T., Stephan, H., Gloe, K., Czugler, M., A new cryptophane receptor featuring three endo-carboxylic acid groups Synthesis, host behavior and structural study. Chem. Eur. J. 2003,9, 1104-1112. 

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