Crown ether derivatives

Crown Ether Derivatives Having Amino Functions.49... 

Sol-gel-derived membranes encapsulating a bis(crown ether) derivative [bis(12-crown-4-ylmethyl) 2-dodecyl-2-methylmalonate] [28] were also fabricated with an initial DEDMS/TEOS ratio of 3 for Na -ISFETs. The Na -ISFETs showed a Nernstian response to Na+ activity changes in the activity range of 1 x 10 " to 1 M and a short response time of 2 s. Employment of a polythiophene interlayer improved the potential instability and the lower detection limit in both of the K - and Na -ISFETs based on the sol-gel-derived membranes with the initial DEDMS/TEOS ratio of 3 (Fig. 8). 

Two new chromogenic crown ether derivatives based on an identical design principle have been synthesized. The lipophilic KBC-002 shown in Figure 23 is a useful new chromo- ionophor for the highly selective calcium determination with cation exchange type optode53. 

E. Lindner, K. Toth, M. Horvath, E. Pungor, B. Agai, I. Bitter, L. Toke, and Z. Hell, Bis-crown ether derivatives as ionophores for potassium selective electrodes. Fres. Z. Anal. Chem. 322, 157-163 (1985). 

A limited number of such ligands have been reported several of these are crown ether derivatives and will be discussed in Chapter 4. 

E. Brunet, A. M. Poveda, D. Rabasco, E. Oreja, L. M. Font, M. S. Batra, J. C. Rodrigues-Ubis, New Chiral Crown Ethers derived from Camphor and Their Application to Asymmetric Michael Addition. First Attempts to Rationalize Enantioselection by AMI and AMBER Calculations , Tetrahedron Asymmetry 1994, 5, 935-948. 

S. Fery-Forgues, M.-T. Le Bris, J.-P. Guette, and B. Valeur, First crown ether derivative of benzoxazinone anew fluoroionophore for alkaline earth metals recognition, J. Chem, Soc., Chem, Commun. 5, 384-385 (1988). 

Cram and co-workers have experimented extensively with chiral recognition in crown ethers derived from various 3-binaphthols (73). In nonpolar solvents, these chiral ethers complex salts of PEA and various chiral a-amino esters (with fast exchange), inducing nonequivalence in their NMR spectra. The senses of proton nonequivalence induced in these solutes have been used to support proposed structures of the diastereomeric solvates (74). 

The chiral 1,2-diols that have been incorporated into crown ether derivatives that cany substituents but have no fused rings associated with the elements of chirality in the macrocycles are listed in Figure 14. We shall now examine some of the ways in which these chiral building blocks have been used. 

In this section, we shall examine the various approaches by which crown compounds that have their chiral elements associated in some way with fused ring systems can be constructed. A selection of the wide and growing range of saturated chiral diols—many of them derived finom readily available carbohydrates—which have been incorporated, as relatively inexpensive sources of chirality, into crown ether derivatives are displayed in Figure IS. It may be noted that the saturated chiral diols rely for their chirality on centers of the classical type (C abcd)—not so the chiral dihydroxy compounds associated with the unsaturated systems listed in Figure 16. These examples reveal that axes and planes of chirality join with less conventional chiral centers (C aaaa) in being sources of chirality in optically active crown ethers. 

The monobenzhydiyl derivative of (S)-binaphthol has played an important role, not only in the synthesis of chiral bisbinaphthyl crown ether derivatives, for example, (55)-124, containing two different bridges between the two binaphthyl units, but also in the provision of an entry into the constimtionally isomeric derivative (5S)-125. Rational stepwise syntheses of macrocyles containing three binaphthyl units have been devised and applied to the synthesis of (SSS)-126 and (RSS)-127. Cleariy, in all these procedures, the C2 symmetry of the chiral building block restricts the number of products (to one ) and defines the symmetries of the macrocycles formed. 

The preparation of phenazine crown ether derivatives was reported by Huszthy and coworkers in their investigation of the use of these heterocycles as enzyme mimics <99T1491,... 

Matsushima, K., Kobayashi, H., Nakatsuji, Y., Okahara, M., Rroton driven active-transport of alkali-metal cations by using alkyl monoaza crown ether derivatives, Chem. Lett., 701-704, 1983. 

Channel-like architectures are formed in the mesophase given by complexes of long chain crown ether derivatives [8.196a,b] and long-chain calixarene derivatives display columnar liquid-crystalline arrangements [8.196c]. Self-assembled tubular structures based on cyclic peptide components have been described [8.186]. 

The effect of Ba2+ or Sr2+ on the substitution of the crown ether derivatives 2, 5, 8, 11, 14 -pcntaoxacyclopcntadccyl-3,6-dioxohcptyl tosylate or 2,5,8,11,14-pentaoxacyclopentadecylmethyl tosylate with MeO, in the form of Me4NOMe, showed that Ba2+ was the better catalyst.127 The kinetics, formation constant, and the interaction of the lariat with the metal cation are discussed. 

In the crown ether derivatives 33, only monotropic phases were observed. All compounds exhibited a very small nematic phase with a relatively broad smectic phase. Decreasing the size of the crown ether unit resulted in higher clearing points... 

The crown ethers were investigated mainly for the removal of Sr or Cs from nuclear-waste streams (246-250), and some studies reported their interest as selective extractants of plutonium (251). Different crown ether derivatives with the addition of alkyl chains have been examined, in order to increase the lipophilicity of the molecule and prevent major extractant losses due to high solubility in aqueous phases. These extractants were described as radiolytically resistant, and their stability increased in the order benzocrown > dicyclohexanocrown > crown (44). 

A. P. de Silva Fluorescent sensing of alkali metal ions by crown ether derivatives... 

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