Macrocyclic amines, reaction

Kinetics and mechanisms of substitution reactions of octahedral macrocyclic amine complexes. C. K. Poon, Coord. Chem. Rev., 1973,10,1-35 (130). 

Copper(III)-aquo and-amine species have been generated by pulse radiolysis [194] but these are transient species that undergo rapid decay. Electrochemical generation of Cu(III) complexes of macrocyclic amines have been reported in acetonitrile [195] but they are also unstable and undergo spontaneous reduction to Cu(II). Nonetheless, it is presumed that copper(III) intermediates are generated as transients in a number of reactions, particularly those involving copper catalysis of multielectron transfer reactions. 

In the case of complexes containing macrocyclic amines, it is often possible to isolate the intermediate deprotonated amido complexes. In the next section, we will consider some very important aspects of co-ordination chemistry, in which reactions of co-ordinated amine and/or amide play a crucial role. 

Sometimes this deactivation is so great that co-ordinated amines are non-nucleophilic. This is particularly likely when the ligand is co-ordinated to a non-labile metal centre. However, even in these cases, all is not lost. We may also use the enhanced acidity of ligands co-ordinated to a metal centre to generate reactive nucleophiles which would not otherwise be readily accessible. For example, nickel(n) complexes of deprotonated diamines may be prepared, and react with dialkylating agents to yield macrocyclic complexes (Fig. 6-10). To clarify this, consider the reaction in Fig. 6-10 in a little more detail. The amine 6.14 is reactive and unselective, and does not give the desired macrocycle upon reaction with the ditosylate. Deprotonation of the amine under mild conditions is not pos-... 

Figure 6-14. The reduction of co-ordinated macrocyclic imines provides a method for the preparation of macrocyclic amines. The reaction above illustrates one of the standard methods for the preparation of cyclam. The metal ion may be removed from the nickel(n) complex by prolonged reaction with cyanide.

Methylene chloride has been found to react rapidly in an. S N2 reaction in a macrocyclic amine via transition state (19)88 The rapid reaction is due to the stabilization of the leaving chloride ion by hydrogen bonding to the NH nitrogens and the interaction between the slightly positive C-H hydrogens and the macrocyclic ether oxygens. A secondary (kn/kD)a = 0.75 confirmed the. S N2 mechanism for the reaction.89... 

Griesbeck et al. have developed the decarboxylative photocyclization (PDC) of phthalimido oo-alkylcarboxylates (15) as a versatile route to macrocyclic ring systems (16). The carboxylate serves as electron donor and C02 is eliminated during the course of the reaction. Applying this concept, the syntheses of medium- and macrocyclic amines, polyethers, lactams, lactones, as well as cycloalkynes were accessible but the limitations... 

A great diversity of imine and amine-imine macrocycle-forming reactions have been reported. Historically significant reactions, see below, continue to be extended, and are still widely used. 

A spontaneous self-condensation of an amine-substituted benzaldehyde takes place in high yield, at room temperature, and without regard to concentration or any other precautions that usually apply to macrocyclic condensation reactions (Martin et al., 1985). The hydroxymethyl substituent of the starting material was first oxidized to the aldehyde, which condensed with the primary amine of another molecule of starting material (method U-17). The resulting bis Schiff base was reduced to form the final dibenzodiaza-crown. 

In this review we focus on applications of the LFDFT method to complexes of 3d metals and compare these with both spectral data from well documented sources [1, 2] and other theoretical methods, such as the spectroscopically oriented Cl (SORCI) method [7] and time-dependent density-functional theory (TDDFT) [8-17]. In particular we intend to emphasize applications to systems with atypical electronic properties of interest for bio-inorganic chemistry and homogeneous catalysis. These systems include macrocyclic amines of Fe in various oxidation states, which are of interest for enzymatic and catalytic reactivity both for redox and bond-breaking reactions. 

The above study has been extended to encompass the synthesis of a new system incorporating differentially substituted macrocyclic subunits (92). Starting from the mononuclear Ni(II) complex of 52 (n = 3) described above, it proved possible to obtain a selective Michael addition reaction between acrylonitrile and the secondary amine groups of the vacant macrocyclic ring. Reaction of the product with Ni(II) yielded the nonsymmetrical complex 53. Based on comparative visible spectral studies, one nickel atom in this complex was assigned a four-coordinate geometry the second appears to be five-coordinate. 

---