Ethers terminal

Fig. 14. Rotaxane dendrimers from crown ether-terminated polypropylimine dendrimer complexation with dibenzylammonium ion...

For instance, the Dow experimental membrane and the recently introduced Hyflon Ion E83 membrane by Solvay-Solexis are "short side chain" (SSC) fluoropolymers, which exhibit increased water uptake, significantly enhanced proton conductivity, and better stability at T > 100°C due to higher glass transition temperatures in comparison to Nafion. The membrane morphology and the basic mechanisms of proton transport are, however, similar for all PFSA ionomers mentioned. The base polymer of Nation, depicted schematically in Figure 6.3, consists of a copolymer of tetrafluoro-ethylene, forming the backbone, and randomly attached pendant side chains of perfluorinated vinyl ethers, terminated by sulfonic acid head groups. °... 

Vinyl ether terminated PIBs with different endgroup structures (I and II in Scheme 16) have been synthesized by Nemes et al. [ 108]. Scheme 16 summarizes the key transformation steps. 

FIGURE 11. Hydroxy-ether terminated carbosilane dendrimer78... 

A study of three Berberis species, namely B. orthobotrys, B. calliobotrys, and B. zabeliana, has yielded four new aporphine dimers, i.e. chitraline (56), 1-O-methylpakistanine (57),67,68 kalashine (58),68,69 and khyberine (59).70 Kalashine and khyberine are the first aporphine-benzylisoquinoline dimers incorporating a diaryl ether terminal at C-ll of the aporphine moiety. 

Fig. 6 Monodendrons based on the 3,5-AB2 arborescence with 3,4-bis( -dodecan-l-yloxy)benzoyl ether terminal groups (X = C02Me, CO2H, CH2OH R = OC12H25)...

The synthesis of single or bis end-capped carbamatosil precursors is straightforward, although it takes some time (a few days). In all cases we used 3-isocyanatopropyltriethoxysilane (ICS) in combination with various polyethyleneglycols or mono-ether-terminated polyethyleneglycols that are commercially available. The synthesis of two single end-capped carbamatosil precursors is described below. 

Other synthetically useful reactions are allylic amination using TsN=Se=NTs and TsN=S=NTs/ photolysis of a/S-unsaturated ketones in the presence of U02Cl2-methanol [e.g. to give (6) cf. Vol. 6, p. 10], " halogenation of enol silyl ethers/ terminal double bond (e.g. geranyl cyanide, carvone) bromination with (7)... 

Ring opening of oxiranes with iodotrimethylsilane provides silylated halohydrins <84CHEC-l(7)in). An exception to this reaction mode has been reported <9iJOC4598>. Silyl enol ether-terminated oxiranes, when treated with TMS-I in the presence of hexamethyldisilazide (HMDS) at low temperatures suffer C—C cleavage and cyclization to dihydrofurans. 

An interesting rearrangement, which appears to be anion-accelerated, takes place in the enol thioether, anion-terminated vinylcyclopropanes of type 14. ° The rearrangement proceeds at — 78 C and is reasonably stereoselective with regard to the final cyclopentene products (syn selectivity 16 1). Regioisomers are encountered in the formation of the dihydrothiopyran cycloaddition adducts 13 in several instances. The mechanism of this rearrangement appears to involve the enol thioether anion in accord with the well-documented donor acceptor principles " and may be related to similar rearrangements observed with trimethylsilyl enol ether terminated vinylcyclopropanes under fluoride ion or Lewis acid catalysis." " ... 

The fluoride-mediated rearrangement of the enol ether terminated vinylcyclopropane 16 to tricyclic ketones 17 and 18 has been featured in a recent synthesis of specionin. Another direction of reaction, a Cope rearrangement, has also been observed in the fert-butyldimethyl-silyl enolates 19 of ketones of type 16. ... 

The development of new polymeric materials for polymer electrolyte fuel cell is one of the most active research areas, aiming at the new energy sources for electric cars and other devices. The mainstream of the material research for fuel cell is perfluoroalkyl sulfonic acid membranes such as Nafion, Acipex, and Flemion. The most well-known one is Nafion of Du Pont, which is derived from copolymers of tetrafluoro-ethylene and perfluorovinyl ether terminated by a sulfonic acid group.Protons, when dissociated from the sulfonic acid groups in aqueous environment, become mobile and the membrane becomes a proton conducting electrolyte membrane. 

Perfluorlnated ion-exchange membranes are derived from copolymers of tetrafluoroethylene (TFE) and a perfluorovinyl ether terminated by a sulfonyl fluoride group. The precursor of the perfluorinated membrane has the form... 

Another approach to a diglycidyl ether of this type which results in a product of improved solubility characteristics is the reaction of two moles of a pure diglycidyl ether of Bisphenol-A with one mole of 2,6-divanillylidene cyclohexanone. This results in a resin with glycidyl ether terminals which is partially soluble in ketone solvents, particularly methyl ethyl ketone. 

Figure 9.4 N-Acyliminium ion pool-initiated polymerization of w-butyl vinyl ether terminated by allyltrimethylsilane...

This transformation of allyl ether terminal groups to propenyl ether terminal groups is very important in practice because during the purification step (the elimination of potassium ion), the propenyl ether is hydrolysed by the acids used for purification to propionaldehyde and a polyether diol [76, 90] ... 

This paper will focus on vinyl ether terminated urethane (VEU) oligomers(20,21). VEU oligomers may be prepared by reacting hydroxy... 

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