Asymmetric induction in the cyclopolymerization of divinyl ethers derived from (R)- or (S)-3,3′-dimethyl-1,1′-bi-2-naphthol

Optically active divinyl ethers, (?)-(R)- and (+)-(S)-2,2′-bis[2-(2-vinyloxyethoxy)ethoxy]-3,3′-dimethyl-1,1′-binaphthyl [(R)- 1b and (S)- 1b ] were polymerized to produce chiral poly(crown ether)s. Their optical rotation was found to be profoundly influenced by the polymerization conditions. When increasing the monomer concentration from 0,1 to 0,3 mol · 1^?1, after polymerization with SnCl₄ in CH₂Cl₂ at 0°C, the optical rotation of the resulting polymers is drastically changed from +44,5° to ?17,3° for (R)- 1b and from ?35,6° to +20,9° for (S)- 1b . The analysis of ¹H NMR showed that the polymers have changed their optical rotation due to a configuration which has a tendency to be preferentially racemic diad at higher monomer concentrations in a nonpolar solvent. There are indications that the twist of 2,2′-binaphtyl moieties, the methyl groups in 3-, and 3′-positions as steric barrier, and the intramolecular solvation of the growing carbo-cation cooperatively control the propagation to induce the asymmetry in the main chain.     

Polymeric chiral crown ethers, 2. Syntheses and chiral recognition of polymers consisting of (S)- or (R)-2,2′-binaphthyl-21-crown-6 units through cyclopolymerization of divinyl ethers

Optically active divinyl ethers, (?)-(S)- and (+)-(R)-2,2′-bis[2-(2- vinyloxyethoxy)ethoxy]-1,1′-binaphthyl [(S)- 1 and (R)- 1 ], were synthesized and polymerized with cationic catalysts. The resulting polymers are composed of only cyclic constitutional units, (S)- and (R)-dinaphtho-[2,1-r:1,2-t]-1,4,7,11,14,17-hexaoxaperhydrocyclohenicosen-8,10-ylene. Both (S)- and (R)-polymers show nearly equal values of optical rotation, but in opposite directions. The ability of chiral recognition of the (R)-polymer towards racemic primary alkylammonium salts was investigated with salts of 1-phenylethylamine, valine, phenylalanine and phenylglycine, and found to be very similar to that of the corresponding model crown ether.     

Polymeric chiral crown ethers, 5. Synthesis of polymers by cyclopolymerization of divinyl ethers containing moieties deriving from L-tartaric acid,and the chiral recognition toward amino acids

The synthesis of polymers with chiral crown ether units containing moieties deriving from L -tartaric acid via cyclopolymerization of divinyl ethers was studied. 1,4-Di-O-benzyl- and 1,4-di-O-trityl-2,3-bis{O-[2-(2-vinyloxyethoxy)ethyl]}-L -threitol ( 1a and 1b ) were polymerized with cationic catalysts to produce polymers ( 2a and 2b ) consisting of only cyclic constitutional units. The trityl groups in polymer 2b were easily cleaved by hydrogen chloride to form a water-soluble, chiral polymer. Polymer 2b was found to complex predominantly with the L -enantiomer of ester salts of phenylglycine, phenylalanine, valine, and methionine in the same way as a chiral polymer incorporating 1,3:4,6-di-O-benzylidene-D -mannitol moieties.     

Asymmetric induction arising from the chiral twist of 2,2′-binaphthyl template in the cyclopolymerization of divinyl ethers

Cationic cyclopolymerization of divinyl ethers, which were derived from (R)- or (S)-1, 1′-bi-2-naphthol with methyl, phenyl, and bromo groups in the 3,3′-positions, yielded polymers with changing optical rotation according to the reaction conditions. Model compounds, therefore, corresponding to the three stereoisomeric forms of the constitutional units, i. e., two racemo (R,R-and S,S-) forms and one meso form, were synthesized to confirm the origin of changing optical rotation in the polymers. ¹H NMR analysis showed that the polymers change their optical rotation due to the configuration, which has a tendency to be preferentially a racemo-diisotactic structure at higher monomer concentrations and in less polar solvents. The chiral twist of the (R)-or (S)-binaphthyl template induces the main chain to form an asymmetric R,R- or S,S-racemo sequence, respectively, in the cyclopolymerization.     

Polymeric chiral crown ethers, 3 Synthesis of polymers incorporating D-mannitol moieties via cyclopolymerization,and chiral recognition towards α-amino acids

A novel approach to the production of chiral, polymeric crown ethers incorporating D-mannitol moieties was developed. Three optically active divinyl ethers (3, 6 and 9) , derived from 1,3 : 4,6-di-O-benzylidene-, 1,2 : 5,6-diisopropylidene- and 1,4 : 3,6-dianhydro-D-mannitol (2, 5 and 8) were polymerized with cationic catalysts. The cyclopolymerization led to the chiral polymeric crown ethers 4, 7 and 10 consisting of only cyclic constitutional units. Both monomer 9 and polymer 10 , containing 1,4 : 3,6-dianhydro-D-mannitol moieties are amphiphilic compounds. Polymer 4 with 1,3 : 4,6-di-O-benzylidene-D-mannitol moieties was found to exhibit chiral recognition in favour of the (S)-isomer of racemic ester salts of phenylglycine, phenylalanine, valine and methionine. The ability of chiral recognition, which was estimated as enantiomer distribution constants (EDC), is comparable to that of polymeric crown ethers with (R)-2,2′-binaphthyl moieties.     

Polymeric chiral crown ethers, 7. Synthesis of polymers incorporating methyl glycosides of α-D-altrose, α-D-galactose, α-D-glucose and α-D-mannose residues via copolymerization of divinyl ethers

Polymers with chiral asymmetric crown ether units ( 5, 6, 7 and 8 ) were synthesized via cationic cyclopolymerization of methyl 2,3-bis{O-[2-(2-vinyloxyethoxy)ethyl]}-4,6-O-benzylidene α-D -altro-, α-D -galacto-, α-D -gluco- and α-D -manhopyranosides ( 1, 2, 3 and 4 ), respectively. The enantioselective transport of the methyl ester of phenylglycine (PhGlyOCH₃) and phenylalanine (PhAlaOCH₃) was examined through a bulk chloroform solution of chiral polymers from one aqueous solution to another. The transport rate of PhAlaOCH₃ was larger than that of PhGlyOCH₃ for every host polymer. For polymer 7 , the optical purity of PhAlaOCH₃ transported from one to the other phase was 12,6%, and the ratio of rate constants for the faster moving enantiomer A and the slower moving enantiomer B (k_A^*/k_B^*) was 1,48. The faster moving enantiomer was the L -isomer except for the systems polymer 7 ? PhAlaOCH₃ and polymer 8 ? PhAlaOCH₃. This enantioselectivity is caused by the diastereotopic faces of the crown ether units in the host polymers.     

Synthesis and properties of poly(ether imide)s derived from 4,4′-(1,5-naphthylenedioxy)diphthalic anhydride and various aromatic diamines

A naphthalene unit-containing bis(ether anhydride), 4,4′-(1,5-naphthylenedioxy)-diphthalic anhydride, was prepared in three steps starting from the nucleophilic nitro-displacement reaction of 1,5-dihydroxynaphthalene and 4-nitrophthalonitrile in N,N-dimethylformamide (DMF) solution in the presence of potassium carbonate. High-molarmass aromatic poly(ether imide)s were synthesized using a two-stage polymerization process from the bis(ether anhydride) and ten aromatic diamines. The intermediate poly(ether amic acid)s had inherent viscosities of 0,66–1,27 dL/g. The films of poly(ether imide)s derived from some diamines, such as p-phenylenediamine, benzidine, and bis[4-(4-aminophenoxy)phenyl] ether, crystallized and embrittled during the thermal imidization process. The other poly(ether imide)s were amorphous materials and could be fabricated into transparent, flexible, and tough films. These poly(ether imide) films had yield strengths of 111–125 MPa, tensile strengths of 96–150 MPa, elongations to break of 10–38%, and initial moduli of 1,6–2,4 GPa. All of these polymers were insoluble in organic solvents, except for that derived from 2,2-bis[(4-aminophenoxy)phenyl]propane. Their T_g's were recorded in the range of 226–265°C by DSC. Thermogravimetric analysis (TG) showed that all the polymers were stable up to 535°C in both air and nitrogen atmosphere.     

Synthesis and characterization of isomeric biphenyl-containing poly(aryl ether bisketone)s, 3. Polymers derived from 3,4′-bis(4-fluorobenzoyl)biphenyl and bisphenols

A series of high-molecular-weight amorphous and semicrystalline poly(aryl ether bisketone)s were prepared from bisphenols and 3,4′-bis(4-fluorobenzoyl)biphenyl via nucleophilic aromatic substitution reactions. Model compound studies were carried out with several substituted monohydric phenols, 3,4′-bis(4-fluorobenzoyl)biphenyl and 3,4′-bis(4-Chlorobenzoyl)biphenyl. The dihalo-substituted aromatic ketones were synthesized by the reaction of 3,4′-biphenyldicarboxylic acid with thionyl chloride, followed by Friedel-Crafts acylation with the appropriate aryl halide. The required dicarboxylic acid was prepared starting from 4-bromotoluene and 3-methylcyclohexanone. Potassium carbonate mediated reaction of the monomers in dimethylacetamide or diphenyl sulfone gave high-molecular-weight polymers in excellent yield. The glass transition temperatures of the polymers are in the 170 to 190°C range. In addition, the polymers exhibit excellent thermal stability, as evidenced by both dynamic and isothermal thermogravimetric analysis, and afford tough films by compression molding.     

Low-molecular-weight poly(imide-amide)s obtained by copolycondensation of 4,4′methylenedi(phenyl isocyanate), trimellitic acid anhydride and benzoic acid in N-methyl-2-pyrrolidone, 1. The microstructure studied by 1H and 13C NMR

Low-molecular-weight poly(imide-amide)s (PIA) obtained by polycondensation at 180°C of 4,4′ -methylenedi(phenyl isocyanate), trimellitic acid anhydride and benzoic acid were studied by ¹H and ¹³C NMR. Complementary ¹H and ¹³C information was used to determine the distribution of II, IA, AA sequences and to show that the repartition of imide (I) and amide (A) groups along the chains is random. According to the composition of the monomer mixture, a slight deficiency of I is reproducibly observed. Non-reacted benzoic acid is found, and unexpected traces of urea and amic acid groups are present in the PIA chains.