Catenanes amide based synthesis

Scheme 10.18 Accidental synthesis of an amide-based [2] catenane.70...

The functionalisation also allows extending the complexity of intertwined molecular assemblies involving molecular catenanes, rotaxanes and knots. Elaborate interlocked assemblies constructed by means of metal-templation techniques and ji-ji-stacking preorganisation were reviewed [3, 11], Our last survey was devoted to the hydrogen bond templated synthesis of amide-based catenanes and rotaxanes [32], Since then a considerable advancement in elucidation of mechanisms of templation and derivatisation of the amide-based interlocked structures has been reached. Moreover, in 2000 we reported a one pot synthesis of amide-based knots such as 8 [21], which is so far the easiest preparation of molecular knots. In the following, specific possibilities of functionalisation of amide-based catenanes, rotaxanes and knots will be discussed. 

Template Synthesis of Amide-based Catenanes, Rotaxanes and Knots... 

Figure 4. Hydrogen bond templated threading of a tetraamide ring in synthesis of amide-based catenanes and...

The amide-based template synthesis of rotaxanes, catenanes and knots were first discovered by Vogtle and coworkers when they tried to synthesize macrocycle 3 [13], The cyclization to yield the tetralactam ring was carried out under high-dilution... 

Scheme 3. Template synthesis by Vogtie and co-workers of amide-based catenanes with a concave template The catenation of the macromonocycle 15 with 13a and 14 leads to formation of catenane 17. The guest diacid dichloride 13a and the host 15 are locked in an orthogonal arrangement 16. The functional groups are fixed and thus preorganized for reaction with the diamine 14.

Physical properties of these poly[2] catenaries have been explored in expectation of unique properties based on the catenane structure [239, 246]. While various interesting physical properties were found in polyrotaxane, no characteristic property has been reported in [2]catenanes so far. Although poly[2]catenane has highly mobile moiety due to the mechanical bond, it has been suggested that the connection between [2]catenane subunit restricted the mobility in motion of [2]catenane. Further, intramolecular interaction in [2]catenane subunit may decrease its mobility. Secondary amide-based [2]catenanes can easily be prepared from commercially available compounds. Takata et al. found that the borane-reduction of the [2]catenanes afforded good yields of the amine-based [2]catenanes that can be useful for polymer synthesis [247, 148] (Scheme 51). Although the origi-... 

Reports of the first amide-based [2]catenanes to be synthesized via simple one- or two-step strategies were made, independently, by Hunter [31, 58] and Vogtle [32, 59]. The straightforward synthesis and easy functionalization of the amide-based [2]catenanes renders them attractive as building blocks for more sophisticated systems [33, 60, 61]. 

The first amide-based oligo[2]catenanes were successfully prepared, via route 2 in Scheme 17.3, by Geerts etol. in 1995 (see Scheme 17.4) [62]. Here, the first stage of the synthesis involved the creation of a dibromide-functionalized [2]catenane, via Hunter s two-step strategy, such that two isomers - IN-OUT 6a and OUT-OUT 6b -were obtained in 5% and 9% yields, respectively. However, due to the inter-molecular hydrogen bonding, the isomeric catenanes were conformationally frozen and could not be interconverted, even at relatively high temperature [60-63]. A... 

Scheme 17.4 Synthesis of amide-based oligo[2]catenanes 8a and 8b.

Scheme 17.5 Synthesis of amide-based poly[2]catenanes 12a and 12b. BnO, benzyloxy group.

Takata et al. reported another very interesting amide-based poly[2]catenane (or oligo[2]catenane) 19 (Scheme 17.8) [57]. Here, the [2]catenane monomer 18 was synthesized in a high yield by utilizing macrocycle-1 as a template (this has proven to be a good templating precursor for the synthesis of catenanes) [56, 82]. Poly[2]catenane 19 was prepared via the Diels-Alder polymerization of 18 at 140°C, without solvent, for several hours. According to GPC analysis with... 

Scheme 17.7 Synthesis of amide-based poly[2]catenane 17. DCC, N,N -dicyclohexylcarbodiimide.

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