Metal-template bond

Template-metal coordinative bonds have also been used in the imprinting and recognition of carbohydrates in aqueous media. A MIP, templated with glucose and using 4-(iV-vinylbenzyl)diethylenetriamine)Cu(H)]diformate as... 

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. 

More versatile reactions are being discovered in metal-templated reactions involving C-N bond formation.21-23 Co-condensation of formaldehyde, nitroethane and the aminothioether 26 in the presence of copper(II) yields an intermediate di-imino nitro macrocycle. Subsequent dissolving metal reduction with zinc in HC1 yields the saturated aza-thia macrocycle 27 in which the hydroxy group and amino groups are /rani-related (Scheme 3.10).22,23... 

The precatenate intermediate can be regarded as a threaded complex, which is thermodynamically stabilized by coordination bonds, from this simple consideration, a transition metal-templated synthesis of rotaxanes was devised, the principle of which is shown in Figure 28 [117]. The threading step (i) is a complexation reaction. 

Curtis and others showed that cyclic condensation also was possible in the absence of a metal template ion, but acid was necessary for those reactions. Possibly, the protonated amines formed an internal hydrogen-bonding network that acted as a template. Cyclization was observed in yields of up to 80% (Curtis and Hay, 1966 Kolinski and Korybut-Daszkiewicz, 1969 Tait and Busch, 1978a, 1978b). The isomers of the formed cyclic Schiff bases were difficult to separate. Reduction of the unsaturated macrocycles gave cyclic polyamines with up to six chiral centers and up to 20 diastereomeric isomers (Hay and Piplani, 1977 Kolinski and Korybut-Daszkiewicz, 1969). 

The oligomerization and cyclooligomerization of dienes is a synthetically useful and commercially significant reaction catalyzed by transition-metal complexes from different triads. In nearly all examples, -allyl complexes are intermediates, formed by either coupling of dienes about a metal template or by insertion of the diene into a metal-H bond. Allyl complexes are isolated from stoichiometric and catalytic diene oligomeriza-... 

---