Rotaxanes templated synthesis

Template synthesis and chirality of catenanes, rotaxanes, and pretzelanes including N-macroheterocyclic lactams and related compounds as structure components 99PAC247. 

Nonionic template synthesis of amide-linked catenanes and rotaxanes with macroheterocyclic fragments 97AG(E)930. 

Schalley CA, WeUandt T, Briiggemann J,V6gtle F (2004) Hydrogen-Bond-Mediated Template Synthesis of Rotaxanes, Catenanes, and Knotanes. 248 141-200 Scheer M,see Balazs G (2003) 232 1-23... 

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. 

In this review, we tried to cover all the supramolecular species that maybe classified as rotaxane dendrimers. We classified them by their structures - where in dendrimer rotaxane-hke features are introduced. Several different types of macrocycles have been employed as a ring component in the templated synthesis of rotaxane dendrimers. While the synthesis of Type I and II rotaxanes dendrimers is relatively straightforward, that of well-defined Type III rotaxane dendrimers, particularly those of second and higher generations, is still challenging. 

Blanco, M.-J., Transition-Metal-Templated Synthesis of Rotaxanes, 23, 125. 

R. Jager, F. Vogtle, A New Synthetic Strategy towards Molecules with Mechanical Bonds Nonionic Template Synthesis of Amide-Linked Catenanes and Rotaxanes , Angew. Chem Int. Ed. Engl. 1997,36,930-944. 

Scheme 13 Templated synthesis of rotaxane 22 employing the threading-followed-by-capping methodology...

Scheme 15 Templated synthesis of rotaxane 24 employing the threading-followed-by-capping methodology. The shift of the proton from the terminal amine to the secondary amine allows for the threading to occur yielding the pseudorotaxane 26... 

Scheme 16 Synthesis of [3]rotaxane 27 by hydrogen-bonding templated synthesis... 

The anion-templated synthesis of rotaxanes first introduced by Vogtle has now been employed by others to produce other interlocked assemblies. Schalley for example [68], has reported an improved yield for the synthesis of rotaxanes by... 

Scheme 21 Anion-templated synthesis of [2]rotaxanes first introduced by Vogtle...

Scheme 24 Templated synthesis of [2]rotaxane 50 by the clipping mechanism...

Schalley CA, Weilandt T, Briiggemann J, Vogtle F (2004) Hydrogen-bond-mediated template synthesis of rotaxanes, catenanes, and knotanes. Top Curr Chem 248 141-200... 

Aucagne V, Bema J, Crowley JD, Goldup SM, Hanni KD, Leigh DA, Lusby PJ, Ronaldson VE, Slawin AMZ, Viterisi A, Walker DB (2007) Catalytic active-metal template synthesis of [2]rotaxanes, [3]rotaxanes, and molecular shuttles, and some observations on the mechanism of the Cu(I)-catalyzed azide-alkyne 1, 3-cycloaddition. J Am Chem Soc 129 11950-11963... 

Hydrogen-Bond-Mediated Template Synthesis of Rotaxanes, Catenanes, and Knotanes... 

The amide hydrogen-bonding motif has been shown to support the clipping, threading, and slipping approaches to the formation of rotaxanes. The wide scope of the neutral template synthesis is enriched by the promising possibilities of the non-template synthesis performed in the melt. Numerous rotaxanes were obtained on a preparative scale and are available for further chemistry. 

Amide-linked catenanes and rotaxanes, readily accessible via nonionic template synthesis, are molecules with fascinating topology, but their final breakthrough was only achieved when they became substrates for further chemical derivatiza-tion. A potential reaction site in the catenanes and rotaxanes presented so far is the sulfonamide group, because the proton can be selectively abstracted in the presence of carbon amide groups. Subsequent alkylation offers numerous possibilities of catenane and rotaxane chemistry. 

Figure 51. Anionic template synthesis of rotaxane 118 with a bis(phenyl ether) axle. The mechanical bond is formed by reaction of the phenolate-macrocycle complex [32-115] (supramolecular nucleophile) with the semiaxle intermediate 117. 

V. Extending the Amide-Based Template Synthesis to Rotaxanes 18 7... 

Fritz Vogtle Barcelona, Spain Rotaxanes, Catenanes. Pretzelanes- Template Synthesis and Chirality... 

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... 

The procedure of the anion-templated synthesis was later used for the preparation of various rotaxanes by the groups of Smith [41] and Schalley [34-36], The anion-templation technique was carefully tested by Schalley et al. Altering the length of the axle-center pieces and the size of stopper groups they synthesized a variety of rotaxanes and analysed their yields and de-slipping rates [34, 35],... 

Schalley, C.A, Reckien, W., Peyerimhoff, S., Vogtle, F. Theory and experiment in concert templated synthesis of amide rotaxanes, catenanes and knots, Chem. Eur. J. in press. 

Figure 1. Different template strategies a) Metal ions, b) 7t-acceptor ft-donor interactions and c) hydrogen bonding mediate the template synthesis of rotaxanes.

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... 

A very surprising and fruitful result was obtained when a control experiment related to an amide templated synthesis was made. Dibromo compound 19 utilized in the reaction looked similar to the axle centerpiece used in the amide template synthesis but lacked the amide in the middle which was crucial for this purpose. However, when the reaction was complete, it was found that rotaxane 24 was formed with 80-95% yield [12] (Figure 9). It seemed reasonable to assume that this time not the axle but the stopper coordinated to the macrocycle [27], This suggestion was supported by the high binding constant of the deprotonated stopper-wheel complex 21 18 (> 105 M"1) derived from H NMR titrations. In the rotaxane synthesis, this complex reacts with the semiaxle 23 producing a rotaxane. 

---