Catenands

Chambron, J.-C., Dietrich-Buchecker, Ch., and Sauvage, J.-P. From Classical Chirality to Topologically Chiral Catenands and Knots. 165, 131-162 (1993). 

Fig. 6.1 Synthesis of a cuprocatenane. High dilution conditions for the second step allow the in-tremolecular condensation of the terminal OH groups on a single phenanthroline. Removal of the metal from the copper(I) complex by treatment with Me4N + CN in acetonitrile/water affords the catenand. Reproduced with permission from C. O. D. Buchecker, J.-P. Sauvage and J.-M. Kern, J. Amer. Chem. Soc. 106, 3043 (1984). (1984) American Chemical Society.

From Classical Chirality to Topologically Chiral Catenands and Knots... 

Table 1. Molecular-weight averages, monomer lengths (/) and estimated upper value of the Kuhn segment lengths (/k) of the poly[2]catenanes 48, 49, and 59, and the poly[2]catenands 51, 56.

Unlike the poly[2]catenanes 48 and 49, the poly[2]catenand 51b, containing catenane segments prepared from large macrocycles (45 atoms) represents the other extreme in view of the high mobility of the macrocycles of die catenane units (Scheme 17) [53, 58], From a synthetic viewpoint, the large mobility of the dihydroxy[2]catenand 50b has a dramatic influence on the resulting polycondensation products (Scheme 18). 

Specifically, the co-polycondensation reaction of the dihydroxy[2]catenand 50b with the terephthalic acid derivative 47 does not proceed to high molecular-weight but affords preferentially the cyclic oligo[2]catenands 52 with n= 1,2,3 as shown by matrix-assisted time-of-flight mass spectrometry (MALDI-TOFMS) [56]. Besides the high structural flexibility of the dihydroxy[2]catenand 50b, an-... 

Scheme 17. Chemical structure of the [2]catenate 50a and the poly[2]catenate 51a, and of their corresponding [2]catenand 50b and poly[2]catenand 51b. The PFg counter-ions have been omitted for clarity.

Scheme 18. Synthesis of the oligo[2]catenands 52 (i) 4-(di-methylamino)pyridine-p- tolu-enesulfonic acid 1 1 complex plus /V,/V -diisopropylcarbodi-imide.

Scheme 19. Synthesis of the poly[2]catenand 51b via demetalation of the poly[2]catenate 51a (i) 4-(dimethylamino)pyridine-p-toluenesulfonic acid 1 1 complex plus AT V -diisopro-pylcarbodiimide (ii) KCN, THF.

Shimada and coworkers recently reported the synthesis of the poly[2]catenand 56, which is structurally related to the poly[2]catenand 51b (Scheme 20) [60]. Similarly to what has been observed for the co-polycondensation of the dihy-droxy[2]catenand 50b with the terephthalic acid derivative 47, the reaction of the diamino[2]catenand 53 with adipoyl dichloride affords mainly the Pretzel -shaped compound 54 [3, 41, 60]. The poly[2]catenand 56 has been obtained via the polycondensation of the diamino[2]catenate 54 with adipoyl dichloride, yielding the poly[2]catenate 55. Subsequently, the demetalation of the latter affords the linear poly[2]catenand 56 with M = 8.1xl05, using polystyrene standards, which corre-... 

Scheme 20. Synthesis of the poly[2]catenand 56 via demetalation of the poly[2]catenate 55 (i) Cu(CH3CN)4BF4, (ii) C10C(CH2)4COCl, (iii) KCN, CH3CN/H20.

It is clear from comparison of the reactivity towards polycondensation of the difunctionalized [2]catenand 50b and 53 with their corresponding difunctionalized [2]catenates 50a and 54, respectively, that the mobility of the interlocked macrocycles of catenanes plays a fundamental role for the nature of the resulting polycondensates - either cyclic oligo[2]catenanes 52,54 or linear high molecular-weight poly[2]catenanes 51b,56 (Schemes 18-20). 

Considering the large variation of / for the poly[2]catenand 51b, it is expected that little correlation will exist between the spatial orientation of neighboring monomer segments and that it will represent the closest synthetic equivalent of the freely jointed chain model [63]. In this model, a real polymer chain is replaced by an equivalent chain consisting of N rectilinear segments of length Z, the spatial orientations of which are mutually independent (Scheme 24) [63]. 

Scheme 24. Snapshot of the conformation of a freely jointed chain (top) and idealized poly[2]catenand 51b [56],...

---