Cyclophanes templated synthesis

Template effects have been used in rotaxane synthesis to direct threading of the axle through the wheel. Since macrocycHc compounds such as cyclodextrins, crown ethers, cyclophanes, and cucurbiturils form stable complexes with specific guest molecules, they have been widely used in the templated synthesis of rotax-anes as ring (wheel) components. Here, we briefly discuss macrocycles used in the synthesis of rotaxane dendrimers and their important features. 

J.-P. Bourgeois, P. Seiler, M. Fibbioli, E. Pretsch, F. Diederich, L. Echegoyen, Cyclophane-Type Fullerene-dibenzo [18] crown-6 Conjugates with trans-1, trans-2, and trans-3 Addition Patterns Regioselective Templated Synthesis, X-ray Crystal Structure, Ionophoric Properties, and Cation-Complexation-Dependent Redox Behavior , Helv. Chim Acta 1999, 82,1572-1595. 

Fig. 5 Distribution scheme for template-directed synthesis of cyclophane 104 +. 60...

Scheme 10.3 Template-directed synthesis of a tetracationic cyclophane by Stoddart and coworkers.

Rozenberg V, Sergeeva E, Hopf H (2004) Cyclophanes as templates in stereoselective synthesis. In Gleiter R, Hopf H (eds) Modem cyclophane chemistry. Wiley-VCH, Weinheim, pp 435 162... 

Stoddart et al. reported the synthesis of the first tetracationic cyclophane-aromatic crown ether-type side-chainpoly[2]catenanes 51 [97,108] via route i (Scheme 17.16). In this case, the dihydroxy-functionalized [2]catenane monomer 50 was first prepared by employing a template method similar to that discussed above. Side-chain poly[2]catenane 51 was prepared by the polymerization of 50 with... 

Although many synthetic routes have been adopted for the preparation of azacycloalkanes and -cyclophanes, the vast majority of cyclization procedures can be grouped into two major categories (i) direct synthesis by conventional organic reactions and (ii) metal ion-promoted (template) reactions. 

It was subsequently discovered that incorporation of a 1,5-dioxynaphthalene residue in the template in place of the 1,4-dioxy benzene moiety causes a dramatic increase in the yield of the cyclophane, an effect that can be further increased using high pressure (12 kbars). The latest improvement in the synthesis of the tetracationic cyclophane—three decades after the first using a template— involved the use of l,5-bis[2-(2-hydroxyethoxy)ethylamino] naphthalene as a replacement for the template mentioned previously because the amine can be protonated and... 

Brown, C.L., Philp, D., and Stoddart, J.F. (1991) The template directed synthesis of a rigid tetracationic cyclophane receptor, Synlett, 462-464. 

The interaction of quinoxalinepodands 156 (Kalinin et al. 2007 Kalinin and Mamedov 2014) with the acetyl moieties and ammonium acetate when heated in DMSO leads to the formation of the macrocyclic system. The process was accompanied by the formation of the pyrrole ring of 161 from the acetyl fragments of 156 and ammonia. The reaction was carried out in highly diluted mixtures in the presence of MgS04, capable of binding water and serving as a template for the synthesis of macrocycles which increases the yields of the cyclophanes 161 from 8-10 to 22-24 % (Table 5.1) (Kalinin and Mamedov 2014). 

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