Applications of Template Reactions

The use of metal ions as templates for macrocycle synthesis has an obvious relevance to the understanding of how biological molecules are formed in vivo. The early synthesis of phthalocyanins from phthalonitrile in the presence of metal salts (89) has been followed by the use of Cu(II) salts as templates in the synthesis of copper complexes of etioporphyrin-I (32), tetraethoxycarbonylporphyrin (26), etioporphyrin-II (78), and coproporphyrin-II (81). Metal ions have also been used as templates in the synthesis of corrins, e.g., nickel and cobalt ions in the synthesis of tetradehydrocorrin complexes (64) and nickel ions to hold the two halves of a corrin ring system while cycliza-tion was effected (51), and other biological molecules (67, 76, 77). 

The ability of crown ethers to bind selectively to particular Group IA and Group IIA metal ions, because of the relationship between hole size and metal ion radius, has led to considerable interest in them in relation to membranes (models for selective ion transport), antibiotics (similar polyether structure), organic synthesis [solubilization of inorganic reagents leading to milder routes for oxidation (122), nucleophilic substitution (123), fluoridation (90)] and extraction of alkali 

The variety of macrocycles that have already been prepared by template reactions (see Sections III and VI) suggest that, in designing a macrocycle synthesis to meet a future need, the use of a metal ion template should not be ignored. 

Acta (Fasciculus Extraordinaries Alfred Werner), p. 174 (1967). 

Department of Chemistry, Birkbeck College, University of London, London, England 

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The influence of the R-substituent nature on the stereochemistry of ICC of type 868 is clearly displayed in complexes of hetaryl azomethinic ligands [15,100,130,134], These chelates are mostly obtained by the method of immediate interaction of ligands and metal salts [(4.48), route A], although some cases of application of template reactions for the same goals are known [(4.48), route B], In this respect, the syntheses (4.48) are representative, described in Refs. 174 and 175 for azo-methines of 3-hydroxybenzo[6]thiophene 878 and their azine analogues, leading to chelates 879 ... 

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