Asymmetric alkylation of carboxyamides by using trans-2,5-disubstituted pyrrolidines as chiral auxiliaries

trans-2,5-Bis(methoxymethyl)- and trans-2,5-bis(methoxymethoxymethyl)pyrrolidines proved to be excellent chiral auxiliaries for the asymmetric alkylation of the corresponding carboxyamide enolates giving good chemical yield and high stereoselectivity (invariably over 95% de), with remarkable flexibility to substrates and reaction conditions.     

Preparation and properties of aromatic polyesters and copolyesters containing phenylindane unit

Aromatic polysters and copolyesters of high molecular weights with phenylindane units were prepared from combinations of 3-(4-hydroxyphenyl)-1,1,3-trimethyl-5-indanol and bisphenol A with isophthaloyl and terephthaloyl chloride by two-phase polycondensation in a nitrobenzene-water system with various phase-transfer catalysts. The phenylindane-containing polyesters and copolyesters were amorphous and readily soluble in a wide range of solvents that included chloroform, m-cresol, tetrahydrofuran, and dimethylformamide. The glass transition temperatures of the phenylindane-derived polyisophthalate and polyterephthalate were 235 and 253°C, respectively, which were higher than those of the corresponding bisphenol A analogs by some 50°C. These polymers began to lose weight around 400°C in air and nitrogen atmospheres.     

Polymerization of α-methylene-N-methylpyrrolidone

α-Methylene-N-methylpyrrolidone (α-MMP) was synthesized and homopolymerized by bulk and solution methods. The poly(α-MMP) is readily soluble in water, methanol, methylene chloride, and dipolar aprotic solvents at room temperature. Thermogravimetric analysis of poly(α-MMP) showed a 10% weight loss at 330°C in air. The kinetics of α-MMP homopolymerization and copolymerization were investigated in acetonitrile, using azobisisobutyronitrile (AIBN) as an initiator. The rate of polymerization R_p could be expresed by R_p = k[AIBN]^0.49[α-MMP]^1.3. The overall activation energy was calculated to be 84.1 kj/mol. The relative reactivity ratios of α-MMP (M₂) copolymerization with methyl methacrylate (r₁ = 0.59, r₂ = 0.26) in acetonitrile were obtained. Applying the Q-e scheme led to Q = 2.18 and e = 1.77. These Q and e values are larger than those for acrylamide derivatives.     

Preparation and configurational isomerism of ditertiary stibine sulfides, (C6H5)(CH3)(S)SbCH2Sb(CH3)(C6H5) and [(C6H5)(CH3)(S)Sb]2(CH2)3

Asymmetric ditertiary stibine sulfides (C₆H₅)(CH₃)(S)SbCH₂Sb(CH₃)(C₆H₅) and [(C₆H₅)(CH₃)(S)Sb]₂(CH₂)₃ have been prepared. It was found that they exist as only one of two possible diastereomers in the crystalline state. However, isomerization to the other form takes place in solution, resulting in an equilibrium mixture. A possibility of configurational lability of tertiary stibine sulfide was suggested for the first time.     

Synthesis of poly-L-naphthylalanine and its secondary structure

Polypeptides derived from L -naphthylalanine and γ-benzyl L -glutamate were prepared. Conformational properties in solution were investigated by circular dichroism (CD) and infrared spectra on the soluble copolymers, and the copolymers were assumed to take the right-handed α-helical conformation. By the addition of trifluoroacetic acid, a transition of side-chain arrangement is induced simultaneously with the conformational transition of the peptide backbone for the copolymer with the highest content of L -naphthylalanine residues. Fluorescence spectra of the copolymers show no excimer emission, which is evidence for the rigid orientation of the side-chain naphthyl groups. The infrared spectrum and x-ray diagram of poly-L -naphthylalanine do not rule out the helical conformation in the solid state.     

Synthesis of polyphthalamides by ring-opening polyaddition reaction of N,N′-disubstituted bisphthalisoimides with diamines

The ring-opening polyaddition reaction of N,N′-disubstituted bisphthalisoimides with various diamines in amide-type solvents at room temperature afforded polyphthalamides having inherent viscosity of up to 0.26 in excellent yields. Some of the polymers thus obtained are a new class of ordered alternating copolyphthalamides. These polyamides were soluble in polar aprotic solvents, as well as in acidic solvents. They showed relatively low melt temperature in the range of 120–220°C and further low level of thermal stability.     

Asymmetric halogenation and hydrohalogenation of styrene in crystalline cyclodextrin complexes

Asymmetric halogenation and hydrohalogenation of styrene in microcrystalline cyclodextrin complexes were studied in the gas-solid state, and compared with the homogenous reactions in aqueous or dimethyl sulfoxide solutions. The gas-solid brominations in the - and -cyclodextrin complexes produced predominantly (–)-1,2-dibromo-l-phenylethane. The chiral induction for the reaction of the -cyclodextrin complex rose to 9 times that of the -cyclodextrin complex. Brominations in the homogenous solutions containing the - or -cyclodextrin complexes gave no dibromide but racemic bromohydrin. In the gas-solid chlorination, the -cyclodextrin complex gave (–)-dichloride,S-(+)-2-chloro-l-phenylethanol (14% ee) and (+)-1,2,2-trichloro-l-phenylethane, and the -cyclodextrin complex produced (+)-dichloride,S-(+)-chlorohydrin (8% ee) and (+)-trichloride. The chiral induction of the gas-solid halogenation using the solid cyclodextrin complexes is attributed to the ability to hold rigidly a chiral conformation of the crystalline state. However, the gas-solid hydrohalogenation all gave racemic products.Presented at the Fourth International Symposium on Inclusion Phenomena and the Third International Symposium on Cyclodextrins, Lancaster, U.K., 20–25 July 1986.     

Separation and determination of traces of heavy metals complexed with humic substances in river waters by sorption on indium-treated amberlite xad-2 resin

A nonionic macroreticular styrene/divnylbenzene copolymer, Amberlite XAD-2 resin is pulverized to 1–10 μm and treated with indium ions to saturate traced of cation exchange sites for the quantitative separation of humic complexes from cations. A 100-ml filtered sample is passed through an indium-treated XAD-2 column (16 diameter, 5 mm tall) at pH 5 at a flow rate of 2 ml min^? to sorb heavy metals complexed with humic and fulvic acids. Inorganic cations and anions, EDTA complexes and colloidal hydrated iron(III) oxide are not retained on the column at all. The heavy metals sorbed on the column are then ultrasonically desorbed with 0.5 M nitric acid and determined by graphite-furnace atomic absorption spectrometry. The results fo two river water samples obtained are in good agreement with those obtained when the macroreticular weak-base anion-exchanger DEAE-Sephadex A-25 is used.     

Synthesis of polyacylsulfonamide-amides by ring-opening polyaddition of N,N′-arylenedisulfonylbissuccinimides with diamines

Ring-opening polyaddition of N,N′-arylenedisulfonylbissuccinimides with both aliphatic and aromatic diamines in N-methyl-2-pyrrolidone at room temperature afforded polyacylsulfonamide-amides having inherent viscosities in the range of 0.2–0.4 in excellent yields. The polymers revealed acidic nature and were readily soluble in both polar aprotic solvents and basic media. They melted at a temperature below 200°C and began to decompose at around 250°C in nitrogen.     

Poly(β-Amino acids). V. Synthesis and conformation of oligomeric α-isobutyl-L-aspartate

α-Isobutyl-L -aspartate oligomers, Z-(α-i-Bu-Asp)_2n–OEt (n = 1–5), where Z = benzyloxycarbonyl and OEt = ethyl ester, were prepared stepwise, and their conformation in solution was investigated by optical rotation, circular dichroism (CD), and NMR spectroscopy. The oligomers up to hexamer existed only in a disordered form. An ordered structure began to appear at octamer and decamer in chloroform and 2,2,2-trifluoroethanol. The ordered structure was more favorable for N-unprotected oligomers, H-(α-i-Bu-Asp)_2n–OEt, in comparison with the corresponding Z-(α-i-Bu-Asp)_2n–OEt. The effects of oligomer concentration and temperature on the structure were slightly observed. The most likely ordered structure was a β form caused by intramolecular association.