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5 6 7 8 Multi-component reactions, which generally mean one-pot processes involving several easily accessible reagents to produce a single product, have become an important area in modern synthetic chemistry. Especially, multi-component reactions involving metal ion, amines, and formaldehyde have been utilized for the preparation of polyaza macrocyclic and macropolycyclic complexes containing N-CH2-N linkages. For instance, the 14-membered hexaaza macrotricyclic complexes [M(2)] (M = Cu(II) or Ni(II)) containing two 1,3-diazacyclopentane rings have been prepared by the reaction (Eq. (1)) of formaldehyde with one kind of triamine (diethylenetriamine) in the presence of the metal ion. Recently, the 15-membered hexaaza macrotricyclic complexes [Cu(3)] and [Cu(4)] have been also prepared by the reaction (Eq. (2) or (3)) of formaldehyde with two different amines. It has been revealed that such one-pot metal-template condensation reactions are useful routes toward various types of polyaza macrocyclic complexes that could not be synthesized by other methods. In most cases, however, formaldehyde reacts with only one or two kinds of amine species. There has been minimal research on the one-pot metaltemplate condensations involving three different amines or more. To the best of our knowledge, [M(6)] (Cu(II) or Ni(II)) is a rare example that prepared from the reaction of three different amines with formaldehyde. Although [M(6)] bearing one N-Me group is prepared by the reaction (Eq. (4)) of formaldehyde with diethylenetriamine, ethylenediamine, and methylamine in the presence of the metal ion, it is formed at best in low yield (~ 10%) because of competing reactions, such as Eqs. (1) and (5). Furthermore, the preparation of other hexaaza macrobicyclic complexes containing bulkier pendant arm, such as N-CH2CH3 or N-CH2CH2CH3 group, could not be achieved; [M(2)] was prepared as the major product when ethylamine or n-propylamine was reacted instead of methylamine. It has been reported that 15-membered hexaaza macrocyclic copper(II) complexes with a 5-6-6-6 chelate ring sequence, such as [Cu(3)], [Cu(4)], and [Cu(5)], are readily decomposed in low pH, unlike the 14-membered macrocyclic complexes [Cu(2)] and [Cu(6)]. Interestingly, their decomposition reaction rates are strongly influenced by the ligand structure. For instance, the reaction rate ratios for [Cu(5)]: [Cu(3)]: [Cu(4)] in 0.3 M HClO4 solution are approximately 1:10:10. However, the reasons for such kinetic behaviors have not been thoroughly investigated, since examples of 15-membered hexaaza macrocyclic complexes with a 5-6-6-6 chelate ring sequence are limited in number. Therefore, we have been interested in the preparation of various types of 15-membered hexaaza macrocyclic complexes with a 5-6-6-6 chelate ring sequence.

One-Pot Reaction Involving Three Different Amines and Formaldehyde Leading to the Formation of New Hexaaza Macrobicyclic Copper(II) Complexes