Poly optically active synthesis

An interesting aspect of the benzofuran cationic polymerization was uncovered by Natta, Farina, Peraldo and Bressan who reported in 196160,61 that an asymmetric synthesis of an optically active poly(benzofuran) could be achieved by using AlCl2Et coupled with (-)j3-phenylalanine, (+)camphorsulphonic acid or with (-)brucine. The optical activity was definitely due to the asymmetric carbon atoms in the polymer chain, indicating that at least some of the polymer s macromolecules possessed a di-isotactic structure, v/ z.62 ... 

Synthesis of Optically Active Poly(l,l -bi-2-naphthyl) 1654c... 

One-shot techniques, 216, 217, 236-237 Optical fiber waveguide, 271-272 Optically active poly(arylene), synthesis of, 518-519... 

Optically active polymers, 473, 479-480 synthesis of, 509 Optically active poly(phenylene-ethynylene), synthesis of,... 

Poly(phenyleneethynylene)s, 482 optically active, 516-517 synthesis of, 496-500, 502 Poly(m-phenylene isophthalamide), 136 synthesis of, 185-186 Poly(l,4-phenylene terephthalate) liquid crystalline polymers, 51 Poly(para-phenylene)s, 472. See also Poly (p -pheny lene)... 

Poly(phenylenethylene), dendronized, 522 Poly(phenylenevinylene) optically active, 510-511 synthesis of, 495-496 Poly(/ ara-phenylenevinylene)s, 472 Polypheny lquinoxaline (PPQ) hyperbranched, 312-314 synthesis of, 309-313 Polyphosphoric acid, 333 Polypropylene oxide) polyol, 223 Polypropylene polyols, 220 Poly (pyridine), synthesis of, 503-505 Polyquinoxaline (PQ), synthesis of, 309-313... 

The preparation of helically well-ordered polymers with stable screw-sense, which is able to be transmitted to newly formed polymer main-chains effectively, is highly desired for the development of new methodology for the synthesis of optically active helical polymers. An aromatizing polymerization of 1,2-diisocyanobenzenes is promoted by methylpalladium(II) complexes, producing poly(quinoxaline-2,3-diyl)s.146-148 The polymerization proceeds with successive insertion of the two isocyano groups of the diisocyanobenzene to the carbon palladium bond of... 

In this section, we comprehensively focused on the controlled synthesis, chiroptical characterization, and manipulation of optically active poly(dialkyl-silane)s. Although many artificial polymers adopting preferential screw sense... 

PolyCy-benzyl L-glutamate) (PBLG), 15 109 Poly(y-ketosulfide)s, optically active, 23 711 Poly(P-alanine), 1 292 Poly-P-hydroxybutyrate (PHB), 12 482 Polybetaines, 20 479-482 applications of, 20 482 preparation of, 20 480-481 solution properties of, 20 481-482 synthesis of, 20 479-481 Polyborates, 4 256-258 Polyborosiloxanes, in silicon carbide manufacture and processing, 22 533 Polybrominated diphenyl ethers (PBDEs), 13 142-143 20 56... 

A research team from Bloemfontein (South Africa) have also taken advantage of the Julia and Colonna oxidation in elegant research aimed at the synthesis of optically active flavonoids. Bezuidenhoudt, Ferreira et al. have oxidised a range of chalcone derivatives using poly-(L)-alanine in the three phase system to afford optically active epoxides 4 which were readily cyclised to target compounds of the dihydroflavinol type 5, (Scheme 3) [16]. 

Another result of great importance—the conformational asymmetric polymerization of triphenylmethyl methacrylate realized in Osaka (223, 364, 365)— has already been discussed in Sect. IV-C. The polymerization was carried out in the presence of the complex butyllithium-sparteine or butyllithium-6-ben-zylsparteine. The use of benzylsparteine as cocatalyst leads to a completely soluble low molecular weight polymer with optical activity [a]o around 340° its structure was ascertained by conversion into (optically inactive) isotactic poly(methyl methacrylate). To the best of my knowledge this is the first example of an asymmetric synthesis in which the chirality of the product derives finom hindered rotation around carbon-carbon single bonds. 

Scheme 16 Synthesis of optically active poly(phenylacetylene) from optically active phenylacetylenes [109]...

Synthesis of monomers for the preparation of the methyl ester polyisocyanides begin with a-amino acid esters. These polyisocyanides were developed to yield optically active polymers which could be characterized first as non-electrolytes, and, after hydrolysis, as polyelectrolytes in aqueous media. As predicted, poly[a(carboxymethyl) alkyl isocyanides] are soluble in various solvents. Unfortunately, a low ceiling temperature, some instability to alkali and especially to... 

Okamoto, Y., Mohri, H., Ishikura, M., Hatada, K., and Yuki, H., Optically active poly(diphenyl-2-pyridylmethyl methacrylate) asymmetric synthesis, stability of helix, and chiral recognition ability, J. Polymer Sci. Polymer Symp., 74, 125, 1986. 

Quaternary ammonium salts of alkaloids have been used for the synthesis of optically active oxiranes from electron-poor olefins under phase-transfer conditions. The enantiomer yield is inversely proportional to the dielectric constant of the solvent,Asymmetric epoxidation in the presence of catalytic amounts of poly-(S)-amino-acids in a triphase system has been described with optical yields up to 96% ... 

McCarthy and coworkers126 229 reported a template-guided synthesis of water-soluble chiral PAn nanocomposites. The nanoparticles were prepared by the physical adsorption of aniline monomer onto a templating poly(acrylic acid) in the presence of (+)- or (-)-CSA, followed by chemical oxidation. Using this approach, optically active nanocomposites of approximately 100 nm diameter were formed. Earlier work by Sun and Yang230 using polyelectrolytes produced similar nonchiral dispersions in which the PAn chain is interwound with a water-soluble polymer by electrostatic forces.231 Similar work by Samuelson and coworkers utilized DNA as a chiral template for PAn.232... 

Optically active synthetic polymers such as poly(trityl methacrylate) supported on silica gel [7,8] as well as poly(ethylene glycol dimethacrylate) cross-linked in the presence of an optically active template [9] have found general use as chiral stationary phases for the optical resolution of various racemates by chromatography. A current area of investigation concerns the use of optically active polymers as reagents and catalysts for asymmetric synthesis [10,11,12]. 

The synthetic synthesis of known chiral polymers mostly starts from optically pure monomers obtained form the chiral pool. The optically pure fermentation product L-lactic acid, for example, is the starting material for the synthesis of poly(L-lactide). However, converting a racemic or achiral monomer quantitatively into a homochiral polymer is less straightforward [3]. This is surprising considering the enormous potential of biocatalysis and tandem catalysis that has emerged in the past decades to prepare optically active intermediates [4]. 

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