Calix catenanes

A chiral [4]pseudocatenane 16 was synthesized from chiral triptycene-based /m( crown ether) and three equivalents of hw[p-(but-3-enyloxy)benzyl]ammonium salt in CH2CI2 in the presence of Grubbs II catalyst, followed by reduction <06CEJ5603>. Several novel calix[4]arenocrowns were prepared by a simple one-pot reaction of calix[4]monohydroquinone diacetate with bw-tosylates, e.g. l,4-bw[2-(2-(2-(2-tosyloxy-ethoxy)ethoxy)ethoxy)ethoxy)benzene, in dry MeCN in the presence of NaOH the self-assembly into calix[4]areno[2]catenanes with a dicationic salt and />-bfr(bromomethyl)-benzene was also demonstrated <06TL6012>. 

The olefin metathesis between alkenyl groups has been frequently used in recent years to stabilize molecules (e.g., dendrimers [46]) or molecular assemblies [47] by additional covalent connectivities [48] and to synthesize macrocydes or more demanding structures like multiple catenanes [24]. Therefore, this reaction was chosen for the connection of alkenyl residues attached to a calix[4]arene via the urea residues. To avoid complications by ds/trans isomerism around the newly formed double bond, the crude reaction mixture was always hydrogenated before working up (Scheme 5.10). 

The synthesis of bis[2]catenanes outlined in Scheme 5.15 allows not only the preparation of compounds with identical loops (12a). The rings attached to the second bisloop calix[4]arene may be also different from those of the first calix[4]arene (12b) [55]. Two regioisomeric bis[2]catenanes are possible, where the two rings attached to a given calix[4]arene are different (Figure 5.12) The isomer 12c can be selectively synthesized from a bisalkenyl urea, where the other two urea functions are connected to a loop, while the third regioisomer 12d would be not so easily available. 

Scheme 5.16 Possible synthetic pathways to calix[4]arene-based multiple catenanes involving trisloop derivatives. 

The principal idea of this present essay was to show how the unique preorganization of functional groups in self-assembled dimers of tetra-urea calix[4]arenes can be used to prepare novel multi-rotaxanes and -catenanes or topologically even more complex molecules and supramolecular structures. We will conclude by summarizing some related studies in which calixarenes were used in a different way as building blocks for the construction of such structures or assemblies. 

Several [2]catenanes incorporating a calix[4]arene unit in their electron-acceptor cyclophane components have also been prepared (see, e.g., Figure 27) [58]. In these compounds, the characteristic charge-transfer bands arising from the donor-acceptor interaction are present, but no luminescence can be observed. 

Recently, two calix[4]arenes were combined to a catenane via loops connecting the oxygen functions in 1,3-position and calixarenes as stoppers were used in a... 

In a further example of interpenetrating systems, the group of Bohmer reported the synthesis and structure of an [8]catenane that forms when two calix[4]arenes self-assemble into a molecular capsule and are then locked in place through reactions of upper-rim substituents [17]. 

Multiple catenanes derived from calix[4]arenes, L. Wang, M. O. Vysotsky, A. Bogdan, M. Bolte and V. Bohmer, Science, 2004, 304, 1312. 

Topologically novel multiple rotaxanes and catenanes based on tetraurea calix[4]arenas 06CC2941. 

Inclusion complexation has developed to becoming another widely exploited supramolecular interaction for the formation of supramolecular polymer networks, mostly in water [197, 198]. Several classes of macrocycles have been developed, including crown ethers [199, 200], porphyrins [201, 202], cyclophanes [203], catenanes [204], cavitands [205, 206], cryptophanes [207], calix[n]arenes [208], and carcerands [209]. Macrocyclic-based supramolecular gels can either be formed from low molecular weight precursors or from macromolecular building blocks. The following discussion focuses on the latter. 

Force Probe MD Simulations of Calix[4]arene Catenanes... 

The successful through-the-annulus threading of calix[6]arene macrocycle induced by the weakly coordinating TFPB anion could be exploited for the synthesis of the first example of a catenane obtained by catenation through the calixarene annulus [28]. In fact, only a few examples of catenanes have been previously reported, in which the calixarene annulus is not catenated at all, but simply acts as a static scaffold on which various catenated macrocycles are constructed, leaving the calix cavity completely unexploited [15a-e],... 

The previuosly described 4 Cla pseudo[2]rotaxane (Fig. 30.3) was the ideal candidate to attempt the synthesis of a calix-threaded [2]catenane by a [1 +1] cyclocondensation clipping with the appropriate diisocyanate derivative 26 (Scheme 30.13). Therefore, pseudo[2]rotaxane 4 cla, previously formed in dry CHCI3 (starting from a 6 x 10 M initial concentration of each precursor), and diisocyanate 3b (6 x 10 M in dry CHCI3) were added, at a rate of 0.6 mL/min from two distinct dropping reservoirs, to 2.0 mL of dry CHCI3 under stirring in the presence of dibutyltin dilaurate (DBTDL) as the catalyst. Under these conditions... 

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