Amines macrocyclic

Shortly after their first report of all-oxygen bridged cryptands, Dietrich, Lehn and Sauvage reported incorporation of sulfur in the strands. The experimental methods used were essentially similar to those applied in the syntheses of the parent cryptands. As in previous cases, a diacyl chloride was condensed with a diamine under high dilution conditions. In this case, however, the diamine contained sulfur atoms rather than oxygen. The synthesis of compound 5 was accomplished in two stages as illustrated below in Eq. (8.3). The first cyclization step affords the macrocyclic amine in 55% yield. The macrobicyclic product (5) is formed in 25% yield from the monocyclic diamine and the acid chloride. 

The new macrocyclic hexaamine ligand X has the mixed protonation constants, log K of 10.10, 10.01, 8.96 and 8.02 at 25 °C and 1=0.2 M for the four most basic amines. The values for other weaker bases, including the six carboxylates, are all less than 5. From a comparison with logA values of the parent macrocycle [18]aneN6, it was deduced that the initial four protonations occur to the macrocyclic amine bases. Thus, the most abundant species of X at neutral pH is depicted as XI. 

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

Probes based on macrocyclic amines include dansylamidoethylcyclen, which can detect zinc at sub-nanomolar concentrations and probes containing xanthene as the chromophore with an ideal wavelength range for intracellular studies.953,962 It is also important that the sensors can differentiate between the alkali metals, which are present at higher concentrations, and zinc. 2, 7-dichlorofluorescein-based sensors have been used in biological systems and reveal concentrations up to ca. 0.3 mM in hippocampal nerve synaptic vesicles.963... 

Reasoning that other macrocyclic materials might also display many of the specific properties of the cycloamyloses, Hershfield and Bender (1972) prepared a macrocyclic amine containing two potentially catalytic hydrox-amic acid groups (16). The aliphatic chains of this material provide a potential binding site similar to the cycloamylose cavity (the diameter of the... 

Although these results have been interpreted in terms of a specific interaction between catalyst and substrate, the precise catalytic mechanism has not been firmly established. Indeed, the possibility that binding outside of the cavity of 16 leads to effective rate accelerations cannot be eliminated. Nevertheless, these preliminary results suggest that macrocyclic amines may surpass their progenitors, the cycloamyloses, in catalytic efficiency, and indicate a potentially fruitful direction for future research. 

The properties of natural macrocycles, the cyclodextrins, has stimulated interest in the preparation of synthetic macrocycles. Three basic types have been made macrocyclic amines, cyclophanes, and cyclic peptides. Hersh-field and Bender (33) prepared a bicyclic amine with hydroxamate sub-... 

Ru=0 stretch. The position of this band is insensitive to the nature of the macrocyclic amine ligand, in accord with the formulation that the electronic transition involves the nonbonding d orbitals (Table 5, Figure 4). Similar electronic absorption bands have also been found for trans-... 

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. 

C. Che u. C. Poon, Pure Appl. Chem. 60, 1201-1204 (1988) Macrocyclic Amine Complexes of Iron, Ruthenium, and Osmium". 

Ligand deprotonation may result in some interesting ambiguities in oxidation state, which ultimately allow us to consider new patterns of reactivity. We begin by considering the iron(m) complex of a macrocyclic amine 5.18. Deprotonation of the amino group in the complex gives an iron(m)-amido complex 5.19 (Fig. 5-34). 

Figure 5-34. The deprotonation of an iron(m) complex of a macrocyclic amine to give an iron(m)-amido complex. The presence of the lone pair of electrons (negative charge) on the deprotonated nitrogen atom is emphasised ( ).

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. 

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.

The Macrocyclic Ligand Effect. A few very recent studies have demonstrated that simple tra/rs-Cc (S )X2 complexes (N4 a macrocyclic amine ligand, X " NH3 or CN ) have exceptionally long lifetimes in fluid solution at room temperature (8, 18,... 

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... 

Hofmann degradation of the quarternary base of the methylammonium salt of Schopf s base IV (66) has been shown to lead to the olefin 67 and the macrocyclic amine 68 (73HCA553). 

Sargeson and co-workers have synthesized, characterized and studied the chemistry of a variety of remarkable macrocyclic amine complexes of RhIH, in which the rhodium is virtually isolated... 

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