Saturated polyazamacrocyclic compounds

Completely saturated tetraazamacrocyclic compounds and their complexes with metals are usually obtained by non-template procedures [159]. Nevertheless, there are two often-used template strategies which show the effectiveness of using reactions on matrices for assembling such systems  

The first is exemplified by the formaldehyde/nitroethane method of macro-cyclisation of c -disposed coordinated primary amines by reaction with HCHO and 

The second route will be considered mainly in the following sections that deal with unsaturated polyazamacrocycles. At the end of this section is illustrated the applicability of this strategy with the particular example of exclusively and efficiently building up small-ring saturated macrocycles. 

The discussion commences with examples illustrating the effectiveness of the first synthetic approach, where the manifestation of the coordination template effect of the metal template is evident. Thus, for instance, interaction of [M(en)2] , where M = Ni, Cu or Pd, with an excess of formaldehyde and carbon acid nitroethane in basic solution gives the cyclam-substituted derivatives [M(L130)] in high yield (Eq. 2.73) [160-162]. 

Two geometric isomers are potentially possible cis (or syn), with nitro groups located on the same side of the macrocycle mean plane trans (or anti), with nitro groups arranged on opposite sides of the macrocycle. In the case of palladium(II) and copper(II) the above reaction is stereoselective in that the anti isomer is preferentially formed. 

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