Azacrowns synthesis

The synthesis of 1,10-diaza-l 8-crown-6 (9) has been an important problem because this is the key starting material in the synthesis of numerous cryptands (see Chap. 8). Although first synthesized some years ago, the process has recently been patented. Di-azacrown 9 is prepared by a high dilution condensation of 1,8-diamino-3,7-dioxaoctane with ethylene glycol diacetyl chloride. The resulting diamide is then reduced with lithium aluminum hydride to give 9 in 56% overall yield from the open-chained diamine. The synthesis is illustrated In Eq. (4.8), below. 

The one-pot synthesis of 9 described above appears to afford only modest yields of azacrowns. One might wonder why any crown at all would be formed under non-high dilution conditions intended to yield only open-chained material. Vogtle suggests that this can be explained in terms of template, steric and entropy effects . These factors are of doubtless significance, but it is interesting to note that in the synthesis of poly-azamacrocycles, Richman and Atkins found that there was no significant template effect observed. The question of the template effect in Ihe syntheses of 9 has recently been addressed by Kulstad and Malmsten They conclude that the formation of 9 is assisted by the presence of alkali metal cations. 

The preparation of novel triazole-containing 20-22 membered macrocyclic azacrown ether-thioethers was reported <96JCR(S)182> and the first selective synthetic method fra the synthesis of dicyanotriazolehemiporhyrazines was published <96JOC6446>. 1,2,4-Triazole-containing polyimide beads were prepared and employed as Mo(VI) epoxidation catalyst supports, liie 1,2,4-nitronyl nitroxide 29 was also synthesized and found to have remarkable magnetic properties <96AM60>. 

Oguz U, Akkaya EU (1997) One-pot synthesis of a red-fluorescent chemosensor from an azacrown, phloroglucinol and squaric acid a simple in-solution construction of a functional molecular device. Tetrahedron Lett 38 4509 1512... 

Ring-opening with heteroatomic nucleophiles is certainly among the most thoroughly studied behavior of epoxides, and this reaction continues to be a versatile workhorse of synthetic utility. This is exemplified in the recent literature by the examples of the p-cyclodextrin-catalyzed aminolysis of simple epoxides by aniline derivatives (i.e., 53 - 54) <00SL339> and the synthesis of oxa-azacrown ethers through the treatment of Ws-epoxides 55 with diamines 56. Yields in the latter synthesis are sensitive to the size of the macrocycle and substitution on the bis-epoxide <00TL1019>. 

P. Bako, K. Vizvardi, S. Toppet, E. V. der Eycken, G. J. Hoonaert, L. Toke, Synthesis, Extraction Ability and Application in Asymmetric Synthesis of Azacrown Ethers derived from D-Glucose , Tetrahedron 1998, 54, 14975-14988. 

Synthesis of the azacrown ether-t)fpe quaternary ammonium salt. 232... 

SYNTHESIS OF THE AZACROWN ETHER-TYPE QUATERNARY AMMONIUM SALT... 

The synthetic versatility of azacrowns (crown ethers with some oxygen atoms replaced with NH functionalities), such as 3.18, has made possible the synthesis of an enormous range of... 

Fedorova, O.A., Gromov, S.P., Pershina, Y.V., Sergeev, S.S., Strokach, Y.P., Barachevsky, V.A., Alfimov, M.V., Pepe, G., Samat, A., Guglielmetti, R. (2000) Novel azacrown ether-containing spiro[indoline-2,3,-naphthoxazines] design, synthesis and cation-dependent photochromism, J. Chem. Soc., Perkin Trans. 2, 563-571. 

Some representative examples of fullerene-porphyrin dyads are shown in Scheme 9. In other examples, porphyrin analogs such as phthalocyanines and subphthalocyanines have been used for the construction of efficient dyads. Again, the most straightforward approach for their synthesis involved 1,3-dipolar cycloaddition of the appropriate azomethine ylides to C60 [203-205]. Also, with the aid of the Bingel reaction, other phthalocyanine-fullerene systems have been prepared [206,207] with the most prominent example being the one that contains a flexible linker possessing an azacrown subunit [208]. The novelty of this dyad can be found in the nature of the linker that could, in principle, induce conformational changes in the multicomponent system when certain ions (e.g., alkaline ions) are present. As a direct consequence this would potentially allow an external control over the electronic interactions between the phthalocyanine and fullerene units. 

The synthesis and use of 7,16-(di-4-pyridinyl)-l,4,10,13-tetraoxa-7,16-diazacyclo-octadecane, prepared from the commercially available azacrown ether and 4-bromopyridine,... 

Although the synthesis and host-guest chemistry of azacrown ethers is well developed their exploitation as molecular catalysts has been comparatively scarce. A... 

Several methods have been developed for azacrown ether synthesis. The most obvious approach was to allow a bifunctional polyether, such as a diiodide, react with an amine. Calverly and Dale used this method to prepare... 

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