Macrobicyclic formation

The macrobicycle formation effect on the reduction potential was calculated in Ref. 345. The following model was proposed the... 

Severin and coworkers reported (146) the reaction of tris(2-aminoethyl)amine and 4-formylphenylboronic acid with penta-erythritol to give, via multicomponent assembly, the boronic acid based macrobicyclic cage 35 (Fig. 25). The cage has the form of an ellipsoid with a diameter of 20.5 A and binds two Cud) ions in a fashion similar to the smaller tren-based cryptands. The reversible formation of boronic esters has also been employed to build other hollow structures such as nanotubes (147) and porous covalent organic frameworks (148,149). 

Table 8. Log K values for M+— macrobicyclic ligand complex formation in aqueous solutiona) (34)...

Cryptands, 42 122-124, 46 175 nomenclature, 27 2-3 topological requirements, 27 3-4 Cryptate, see also Macrobicyclic cryptate 12.2.2], 27 7-10 applications of, 27 19-22 cylindrical dinuclear, 27 18-19 kinetics of formation in water, 27 14, 15 nomenclature, 27 2-3 spherical, 27 18 stability constants, 27 16, 17 Crystal faces, effect, ionic crystals, in water, 39 416... 

The crystal structure 57 of the strong and selective complex formed by the terephthalate dianion with a hexaprotonated macrobicyclic polyamine shows that it is a molecular cryptate 56 with the dianion tightly enclosed in the cavity and held by formation of three hydrogen bonds between each carboxylate and the ammonium groups [4.19]. Both structures 53 and 57 illustrate nicely what supermolecules really are they show two covalently built molecules bound to each other by a set of non-covalent interactions to form a well-defined novel entity of supramolecular nature. Acyclic [4.20a,b] and macrobicyclic [4.20c] hydrogen bonding receptors... 

A macrobicyclic thiazolium cyclophane 84 functions as a model of thiamine pyrophosphate-dependent ligases and effects benzoin condensations [5.38, 5.65a, A.l 1], Acyl transfer is catalysed by formation of a ternary complex between a cyclophane receptor and two substrates [5.65b]. 

In order to gain more direct access to these bicyclic ligands, methods have been developed which allow the formation of the macrobicycle in one step. The tripod-tripod coupling is an example of this method (Fig. 5.2) which may be performed without the need for high-dilution conditions. The synthesis of the bis-tren macrobicycle, 17, illustrates this approach.3... 

A significant cesium effect was observed in reactions forming C—N bonds leading to macrobicyciic compounds. Lehn et al. [34] synthesized the nona-tosylaza macrobicycle 19 in a one step reaction by a threefold bond formation combining the two triply functionalized building blocks 17 and 18. The cryptand 19 was... 

In the majority of cases, the formation of macrobicyclic metal tris-dioximates is stipulated by the interaction of the reactive oxime groups in tris-dioximate complexes with Lewis acids. The most efficient capping agents have proved to be trigonal organic and inorganic boron compounds. 

Synthesis of macrobicyclic MDma(BR)2 complexes (where M is nickel (paramagnetic), iron and cobalt ions R is CeHs and re-C4H9) was reported by Umland and coworkers [38]. However, the formation of nickel complexes of this type was not further confirmed. 

In the case of cyclohexanedione-1.2-dihydrazone, the macrobicyclic dihydrazonate formation proceeded on the template Fe-+ ion more... 

The binuclear germanium-capped clathrochelate [Fe2DA03(Ge(CF3)3)2] oximehydrazonate was obtained by a template condensation of the tetradentate H2DAO ligand with IGe(CF3)3 in an aqueous solution in the presence of CaCOs (Reaction 52). The resulting intramolecular macrobicyclic compound precipitated from the reaction mixture, and the equilibrium shift due to the formation of the solid allowed one to isolate this complex in a relatively high yield [73]. 

The use of 3,3 -thiodipropionicacylchloride instead of bis-(3-tosyloxy-propyl)tosylamine in the first step led to the formation of a macrobicyclic N4S-pentadentate ligand (Scheme 97). 

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