Polyethers containing

Macrocyclic polyethers containing the 2.2-paracyclophane unit are interesting structures and several such compounds have been prepared . Despite the diverse structural possibilities, the syntheses of these molecules have generally been accomplished by straightforward Williamson ether syntheses. The only unusual aspect of the syntheses appears to be a novel approach to certain paracyclophanes developed by Helgeson (see footnote 7a in Ref. 91). The first step of Eq. (3.28) illustrates the formation of the required tetrol, which is then treated with base (KOH or KO-t-Bu) and the appropriate diol dito-sylate to afford the macrocycle. 

F.D. Konstandakopoyloy and J.K. Kallitsis, Soluble rigid-flexible polyethers containing bis (biphenyl)anthracene or bis(styryl)anthracene units in the main chain for light-emitting applications, J. Polym. Sci., Part A Polym. Chem., 37 3826-3837, 1999. 

The selectivity of 8-HQ and 8-HQS is poor, but can be improved by appropriate substitution on the oxygen atom to form acyclic polyethers containing two oxy-quinoline fluorophores, as in compounds M-3 and M-4 shown in Figure 10.27. The geometrical constraints in these compounds explain the excellent selectivity for the small lithium ion. 

More than sixty neutral macrocyclic polyethers containing four to twenty oxygen atoms, each separated from the next by two or more carbon atoms, have been synthesized 40, 41) (see Fig. 8). Many of these compounds form 1 1 complexes in which the cation is encircled by the oxygen atoms of the polyether 44, 71). The potassium complex of di-benzo-30-crown-10 (77) consists of a wrap-around structure, where all the oxygen atoms are approximately equidistant from the central... 

Log K data for the reaction of several cations with cyclic polyethers containing 5 and 6 oxygen donor atoms are given in Table 4. The log K values for 15-crown-5 complexes are smaller than corresponding values for 18-crown-6 in the cases of K+ and Ag+. However, the affinity of the ligand for Na+ relative to K+ markedly increases as cavity size... 

Polyether containing 2,2 -bipyridil units 8 spontaneously forms a double helicate 9 by multiple coordination with Cu+ ions [13]. This process of self-organization is enforced by the proper orientation of coordinated bipyridyl units analogous to that shown in Figure 1.2. It is characterized by a positive cooperativity yielding no partly assembled species. 

Polysulfone Plastics. These plastics which were commercialized by Union Carbide are actually aromatic polyethers containing periodic sulfone groups which provide additional resonance stabilization. They have good mechanical properties, creep resistance, and dimensional stability but their outstanding quality is their high heat distortion temperature (345°F.) and resistance to thermal oxidative degradation. Limitations are difficult thermoplastic processability, amber color, and sensitivity to organic solvents. 

The polyetherification route to polyethersulfones can be adapted to the synthesis of polyethers containing strongly electron-withdrawing groups other than sulfone groups. Poly(l,4-oxyphenylenecarbonyl-l,4-phenylene) [27380-27 4] (6) is produced by condensation of 4,4 -dihydroxybenzophenone or by the self-condensation of 4-chloro-4 -hydroxybenzophenone. It has a melting point of 367°C and a glass-transition temperature of 154°C (83). 

The THECOMAC database contains the stability constant, enthalpy, and entropy values for the complexations of the alkaline and alkaline earth metal cations with cyclic polyethers in water and organic solvents, and includes more than 3,500 records. Each record contains 22 textual and digital fields and 2D chemical structures of ligands. The database includes thermodynamic values for 330 cyclic polyethers containing oxygen coordination centers only.41... 

Figure 22.6 Polyethers containing lithium aluminate groups.

The [2]catenane 19" + incorporates (Figure 31) a macrocyclic polyether containing two dioxybenzene units, and a tetracationic cyclophane comprising a bipyr-idinium and a ram-bis(pyridinium)ethylene unit [36a, 62]. The H NMR spectrum [(CD3)2C0, 213 K] of 19" + shows the signals for two distinct co-conformations in a ratio of 92 8. In the major isomer, the bipyridinium unit is located inside the cavity of the macrocyclic polyether and the ra 5-bis(pyridinium)ethylene unit is posi-... 

The third situation is illustrated in Figure 11 and also refers to a different case in which the monomeric unit displays only a virtual mesophase. Here as before, the slope of the T. (i.e., Tic k) M dependence is higher than that of the Tffl (i.e., T j -M dependence, the latter lies above the former throughout hence the two curves do not intercept each other. Therefore, the resulting polymer displays also only a virtual mesophase. This thermodynamic situation was recently applied to the synthesis of virtual liquid crystal polyethers containing both flexible mesogens and flexible... 

The reaction of carbonyl compounds and allylmetal reagents is an important transformation in organic synthesis. Advances in stereoselective carbonyl allylation reactions have been spurred by interest in the synthesis of polypropionate-derived natural products, carbohydrates and other polyhydroxylated compounds. These reactions are ideally suited for the construction of stereochemically rich acyclic skeletons. Additionally, cyclic polyether-containing natural products, among others, have inspired chemists to investigate ring-closing allylation reactions. This review will focus on recent developments in the allylation reaction, with special emphasis on its application towards the synthesis of natural products. 

Examples are the 1, l -dibenzyl-4, 4 -bipyridinium electron-acceptor dication threaded into the 1, 5-dinaphtho-38-crown-10 (Fig. 2a) [10], and the acyclic polyether containing a dioxybenzene electron-donor unit threaded into the electron-acceptor cyclobis(paraquat-p-phenylene) tetracationic cyclophane (Fig. 2b) [11]. Although in these cases a large contribution to the association driving force comes from the electron-donor/acceptor (charge-transfer, CT) interactions, hydrogen bonding can also play an important role, as clearly shown in the cases of pseudorotaxanes constituted by 4, 4 -bipyridinium [12a] or l,2-bis(pyridinium)ethane [12b] threads and crown ethers. 

A series of polymers (including polysulphones, polyethers) containing the monomer fra s-l,2-diphenylcyclopropane have been synthesised [49] by solution polycondensation. CP/MAS spectroscopy was used, among other techniques, to characterise the cyclopropane ring opening reaction which had occurred in the final thermally crosslinked product. One such polymer (Fig. 15.2.45) showed characteristic peaks in its CP/MAS spectrum (Fig. 15.2.46). 

The resulting crude, alkaline polyether contains around 0.2-0.3% of the KOH used as the catalyst. The idea of polyether polyol purification is to remove as much as possible of the alkaline ions until a very low level of 5-10 ppm (the requirements for industrial polyether polyols are < 5 ppm) is left. 

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