Giant macrocycles

The "zip-reaction (U. Kramer, 1978, 1979) leads to giant macrocycles. Potassium 3- ami-nopropyl)amide = KAPA ( superbase ) in 1,3-diaminopropane is used to deprotonate amines. The amide anions are highly nucleophilic and may, for example, be used to transam-idate carboxylic amides. If N- 39-atnino-4,8,12,16,20,24,28,32,36-nonaazanonatriacontyl)do-decanolactam is treated with KAPA, the amino groups may be deprotonated and react with the macrocyclic lactam. The most probable reaction is the intramolecular formation of the six-membered ring intermediate indicated below. This intermediate opens spontaneously to produce the azalactam with seventeen atoms in the cycle. This reaction is repeated nine times in the presence of excess KAPA, and the 53-membered macrocycle is formed in reasonable yield. 

It should also be noted that, although most of the polymers discussed in this chapter are assumed to be linear open-chain structures, the possibility also exists that giant macrocyclic species or chain-linked macromolecules may also exist.1 Such species would be very difficult to distinguish from linear high polymers. Linear polymers have end groups that, in theory, might be detectable by NMR techniques, but in practice the chains are... 

Fig. 19 Formation of giant macrocycles by self-coordination of ferrocene-bridged zinc trisporphyrin units...

K. Nakao, M. Nishimura, T. Tamachi, Y. Kuwatani, H. Miyasaka, T. Nishinaga and M. lyoda. Giant macrocycles composed of thiophene, acetylene and ethylene building blocks, J. Am. Chem. Soc., 128, 16740-16747 (2006). 

Macrocycles are sometimes only formed in the presence of monomers. When all monomer has been consumed by polymerization, depolymerization also stops [333]. The tendency of common heterocycles to the production of giant molecules, and the possibility of generating cyclic fractions from their chains is illustrated in Table 6. 

Figure 8 A giant hexameric porphyrin-containing macrocycle and the template that is used for its formation.

Williams-Hany M, Bhaskar A, Ramakrishna G, Goodson T, Imamura M, Mawatari A, Nakao K, Enozawa H, Nishinaga T, lyoda M (2008) Giant thienylene-acetylene-ethylene macrocycles with large two-photon absorption cross section and semishape-persistence. J Am Chem Soc 130 3252-3253... 

Postpolymerization modification of PM and the use of structurally novel borane initiators provide control of polymer topology and synthesis of novel PM architectures. Examples including three-arm star polymers, giant tube-like structures and macrocycles are illustrated below. 

An interesting development in monomer synthesis and subsequent polymerization was disclosed earlier this year [51. A synthetic route for preparing giant rings containing about 20 to 40 monomer units was devised. These macrocycles could be polymerized directly to high molecular weight polymers (Equation 3). 

Hui JKH, MacLachlan MJ (2(X)6) [6+6] Schilf-base macrocycles with 12 imines giant analogues of cyclohexane. Chem Commun 42 2480-2482... 

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