Azacrown compounds

A number of azacrown compounds were reported by Lockhart and coworkers in 1973. In a typical case, 2-aminophenol was heated at reflux with an equivalent of tet-raethylene dichloride for 48 h. A mixture of the monoaza-15-crown-5 (5) and the mono-aza-12-crown-4 (4) shown in Eq. (4.4) were obtained. Structural assignments were based on H-NMR, IR and mass spectral data. 

Although the clam structures are of interest as ammonium ion binders, they are by no means the only azacrown compounds of interest in this application. Sutherland and coworkers have examined a number of azacrowns as primary ammonium ion bind-ers - . In addition, Metcalfe and Stoddart have utilized bis-azacrowns to bind secondary ammonium cations. 

Thus the assembly is pre-organized for metal ion uptake and no counter-anion transport into the organic phase is necessary. In other studies, it has also been demonstrated that another self-organization process involving azacrown compounds has allowed metal salt extraction against that counters the Hofmeister series for the anions involved [50]. 

Fig. 4.17. General scheme for metal extraction on the basis of a 2 1 assembly between a carboxylic acid and an azacrown compound.

The 24- to 32-membered azacrown compounds described by Lehn et al. proved to be effective host substances for organic guest ions in water solution For example... 

Conversion of dipeptides and tetrapeptides into macrocyclic functionalised azacrown compounds by means of caesium-assisted ring closure of JV-2-chloroacetyl derivatives was carried out according to Scheme 6-8 [170], to obtain L1490 and L1491 (Eq. 6.61). 

Countless macrocycles containing basic functionalities have been synthesized and, for a large number of compounds, values have been determined (Patai, 1980 Gokel and Korzenowski, 1982 Kaden, 1984 Kimura, 1985 Lindoy, 1989 Vogtle, 1989, 1991 Gokel, 1991, 1992 Izatt et al., 1991, 1992 Dietrich et al., 1993). Usually, the basic function in these macrocycles is a nitrogen atom the compounds are (poly)azamacrocycles. But in azacrowns like [1] or cyclams [2] the /n-orientation of the lone pair at the nitrogen atom is not assured. Murakami et al. (1991) synthesized the... 

Axle and collar molecular structure, 27 60-61 Axokine, 3 97 Azaboranes, 4 170, 204 Azacarbocyanine dyes, 9 257 Aza[18]crown-6, 24 41 Aza[18]crown-6 appended a-helical barrels / rods, 24 58 Azacrown ethers, 24 44 Azacrowns, 24 41 Azacryptands, 24 42 Azadirachtin, 24 474 Azafullerenes, 22 231, 232, 243 Azahomofullerenes, 22 243 Azaindene compounds, 29 197 Azalactone method (for Emphaze supports), for covalent ligand immobilization, 6 396t Azamethiphos (salmosan)... 

The compounds [9] and [10] were synthesized in an effort to increase the through-space interaction between the ferrocene moiety and the bound cation (Scheme 3). These ligands were prepared by reaction of two equivalents of the corresponding mono-azacrown ether with bis(chlorocarbonyl)ferrocene. 

The bis-sulphonamide (0.02 mol) and the a,o-dibromo compound (0.02 mol) in PhH (or PhMe) (600 ml) are added to a refluxing two-phase system of aqueous NaOH (7.5%, 100 ml) and PhH (or PhMe) (100 ml) containing TBA-I (1.85 g, 5 mmol). The mixture is stirred under reflux for 8-10 h and then cooled to room temperature. The organic phase is separated, dried (MgS04), and evaporated to yield the A-tosyl azacrown ether which, upon treatment with acid, is converted into the azacrown ether. 

The aminolysis of pentalenes 50 with aliphatic diamines or azacrown ethers, which play the role of diamines, results in A,iV -bis(diazatrithiapentalenyl)diamines 51 and azacrown ether derivatives 52. Aryloxy groups in diamines 51 can be also substituted by NR2R3 fragments. A combination of azacrown ethers and different diamines results in compounds 32, 53, and 54 (Scheme 4) <1994CB2209, 1994PS81>. 

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