Crown ethers and derivatives

Liquid-liquid PTC would seem to be convenient for the synthesis of crown ethers and derivatives. But most still use conventional conditions,28,29 probably because the synthesis of macrocyclic crown ethers gives better results when Na+ or K+ ions are involved. These ions can induce a template effect with the polyethyleneoxy chain 63. 

The nuclear industry has been a major focns for research involving crown ethers. In addition to the well-known radioactive actinide byproducts, such as uranium and plutonium oxides, other radioactive species are associated with the industry. Sr and Cs are found in low-level acidified nuclear waste and can be targeted by crown ethers and derivatives, chief among them being the calixcrowns. ... 

Figure 2 Representative structures of macrocyclic receptors, (a) Crown ethers and derivatives, (b) a- CDs, (c) calixarenes w = 4, 6, 8.

Figure 3 Structures of crown ether and derivatives in sensors.

The first three-dimensional macrobicyclic TTF derivatives have been obtained <96CC615> and work on TTF-containing crown ethers and thioethers has continued <96LA551, 96JCS(P1)1995> with structures of this type being used to obtain the first TTF-containing... 

Various types of research are carried out on ITIESs nowadays. These studies are modeled on electrochemical techniques, theories, and systems. Studies of ion transfer across ITIESs are especially interesting and important because these are the only studies on ITIESs. Many complex ion transfers assisted by some chemical reactions have been studied, to say nothing of single ion transfers. In the world of nature, many types of ion transfer play important roles such as selective ion transfer through biological membranes. Therefore, there are quite a few studies that get ideas from those systems, while many interests from analytical applications motivate those too. Since the ion transfer at an ITIES is closely related with the fields of solvent extraction and ion-selective electrodes, these studies mainly deal with facilitated ion transfer by various kinds of ionophores. Since crown ethers as ionophores show interesting selectivity, a lot of derivatives are synthesized and their selectivities are evaluated in solvent extraction, ion-selective systems, etc. Of course electrochemical studies on ITIESs are also suitable for the systems of ion transfer facilitated by crown ethers and have thrown new light on the mechanisms of selectivity exhibited by crown ethers. 

The condensation reactions described above are unique in yet another sense. The conversion of an amine, a basic residue, to a neutral imide occurs with the simultaneous creation of a carboxylic acid nearby. In one synthetic event, an amine acts as the template and is converted into a structure that is the complement of an amine in size, shape and functionality. In this manner the triacid 15 shows high selectivity toward the parent triamine in binding experiments. Complementarity in binding is self-evident. Cyclodextrins for example, provide a hydrophobic inner surface complementary to structures such as benzenes, adamantanes and ferrocenes having appropriate shapes and sizes 12) (cf. 1). Complementary functionality has been harder to arrange in macrocycles the lone pairs of the oxygens of crown ethers and the 7t-surfaces of the cyclo-phanes are relatively inert13). Catalytically useful functionality such as carboxylic acids and their derivatives are available for the first time within these new molecular clefts. 

It should be noted that selective carrier facilitated transport experiments involving the crown ethers and their derivatives have not been... 

The chemistry of a-haloketones, a-haloaldehydes and a-haloimines Nitrones, nitronates and nitroxides Crown ethers and analogs Cyclopropane derived reactive intermediates Synthesis of carboxylic acids, esters and their derivatives The silicon-heteroatom bond Syntheses of lactones and lactams The syntheses of sulphones, sulphoxides and cyclic sulphides... 

In this study, we report synthesis of a new thiourea derivative (2) which contain crown ether and phenanthroline ring by the reaction of 5-amino-1,10-phenanthro-line with 15-isothiocyanatobenzo[15-crown-5] (1) (Fig. 43.1) and its complex with Cu(I) is obtained. The structures of the ligand and the complex were determined by their elemental analysis, UV-vis, FTIR, H NMR (DMSO-d ), C NMR (DMSO-dg) and Mass spectra (LC-MS). 

Figure 3. Salt effects on cloud points of N-alkyl monoaza crown ethers and the corresponding open chain derivatives (from Kuo and Okahara, Ref. 22. 1983)...

Darzens condensation using crown ethers and cinchona alkaloids-derived catalysts, respectively, obtaining epoxides with moderate enantioselectivity. 

Crown ethers and cryptands show much of the same functional group chemistry as simple ether- or amine-containing molecules. The remarkable reactivity of these macropolycyclic species is primarily derived not from the composition of functional groups but from their three-dimensional arrangement. The important property of strong cation complexation is determined by the topology of the cavity defined by the ether and amine groups in the molecular superstructure. 

The present contribution deals mainly with novel 9-substituted anthracenes in which the substituent either incorporates or by itself represents a 7r-system, and whose effect on the overall molecular shape is such as to have major photochemical and photophysical repercussions [33]. Not discussed are anthracenophanes [34] and various types of bichromophoric anthracenes whose excited state properties have been reviewed previously [8,25,35]. Considered beyond the scope of this contribution are the photochemistry and photophysics of anthraceno crown ethers and cryptands [36-38], and of intramolecular exciplexes derived from anthracenes linked to aromatic amines [39-41],... 

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