The reaction between diethyl succinylsuccinate (1,4-diethoxycarbonyl-2,5-dihydroxy-1,4-cyclohexadiene) and amines and its application to polymer synthesis

Polymers having polyamine structures were obtained by the condensation reaction between diethyl succinylsuccinate (1,4-diethoxycarbonyl-2,5-dihydroxy-1,4-cyclohexadiene) and aliphatic diamines. The reactions were carried out in high polar solvents such as N-methylpyrrolidone (NMP) and N,N-dimethylformamide (DMF). The mode of the polymerization reaction and the structure of the polymers were verified by studies of model compounds. The polymers thus obtained were conveniently utilized as coating and adhesive materials and were able to be cast into films.     

Direct polycondensation of hydroxybenzoic acids with diphenyl chlorophosphate in the presence of ethers

The effects of a modification of the relative reactivity of carboxyl groups to hydroxy groups in monomers on the direct polycondensation of hydroxybenzoic acids was investigated. Polycondensation with diphenyl chlorophosphate (DPCP) was largely promoted by carrying out the reaction in the presence of ethers which are capable of complexing with carboxyl groups in the monomers. The amount of alkyl ethers, such as, poly(ethylene oxide) (PEO) corresponding to an equivalent unit mole of carboxyl groups was effectively added. The molecular weights of the polymers produced increased with the higher molecular weights of PEO, showing maximum values by use of PEO of 1–2.5 × 10⁵.     

Direct polyesterification promoted by a complex of diphenyl chlorophosphate with LiBr

The diphenyl chlorophosphate (DPCP)-promoted polycondensation reaction between aromatic dicarboxylic acids and bisphenols was largely improved by carrying out the reaction in the presence of lithium halides to give high molecular weight aromatic polyesters. Among the halides LiBr, which is capable of forming a complex with hexamethylphosphoramide, was most effective, suggesting that a similar complexation of DPCP with LiBr in pyridine facilitates the complete reaction of DPCP with carboxyl groups. The complex could selectively activate carboxyl groups of hydroxybenzoic acids to give high molecular weight copolyesters from several combinations of aromatic hydroxy acids. The reaction could also be adaptable to the copolycondensations of a mixture of the dicarboxylic acids, bisphenols, and hydroxybenzoic acids.     

Direct polyesterification promoted by a complex of phosphorus oxychloride with LiCl monohydrate

The reaction of benzoic acid and p-chlorophenol with phosphorus oxychloride (POC) was significantly affected by the presence of metal salt hydrates or a mixture of metal salts and water sufficiently aged. Among metal salts examined, LiCl was most effective for the reaction to give quantitative yield of the benzoate. The reaction was assumed to proceed via a complexation of POC with LiCl monohydrate followed by selective hydrolysis of POC by water bound to LiCl. The reaction promoted by a complex derived from POC and LiCl monohydrate in pyridine was successfully used as a new condensing agent for the synthesis of aromatic polyesters by the direct polycondensation or aromatic dicarboxylic acids and bisphenols. Under favorable conditions for aging of POC with LiCl monohydrate and for addition of bisphenols, polymers of moderate to high molecular weights were obtained in quantitative yield. The reaction was applied with limited success to the preparation of a copolymer of high molecular weight from hydroxybenzoic acids.     

Direct polyamidation with phosphorus oxychloride in pyridine

Direct polycondensation of aromatic dicarboxylic acids and diamines with phosphorus oxychloride (POC) was successfully carried out to give polyamides of high inherent viscosity, when POC was reacted selectively and completely with a two molar quantity of carboxyl groups. To achieve the selective and complete reaction, factors, such as the amount of POC used, reactions of POC with the dicarboxylic acids by adding of POC to the acids or its reverse addition under various conditions, and aging after addition were fully examined. The reaction was proposed to proceed via a bifunctional cyclic phosphoric–carboxylic anhydride through stepwise reaction of POC with carboxyl groups.     

Solution synthesis of human peptide YY (hPYY)

Human peptide YY (hPYY) was synthesized in a conventional manner by assembling six peptide fragments followed by deprotection with 1 M trimethylsilyl trifluoromethanesulfonate (TMSOTf)-thioanisole in trifluoroacetic acid (TFA). After purification by gel-filtration on Sephadex G-25, followed by reversed-phase high-performance liquid chromatography, a highly purified sample of synthetic hPYY was obtained. When administered in dogs, synthetic hPYY was as active as synthetic porcine PYY in terms of the effects on systemic arterial blood pressure, and splanchnic blood flow.     

High-molecular-weight poly(amino acid)s by the direct polycondensation reaction promoted by triphenyl phosphite and LiCl in the presence of polyvinylpyrrolidone

Poly(α-amino acid)s of high molecular weight were obtained by the direct polycondensation reaction of α-amino acids in the presence of polyvinylpyrrolidone (PVP) as a matrix of triphenyl phosphite and LiCl in N-methylpyrrolidone (NMP). Molecular weights of the polymer produced were improved by use of an increasing amount of matrix of higher molecular weight. Most favorable results were obtained by the reaction at 80°C for 16 hr at a monomer concentration of 0.33 mole/liter in a NMP solution that contained about 3 wt % LiCl in the presence of an equivalent unit mole of PVP with the molecular weight of 3.6 x 10⁵. The polymer from β-alanine with high molecular weight, which is difficult to obtain by the NCA method, was easily prepared by this process.     

Landau-pomeranchuk-migdal air showers initiated by ultra-high-energy neutrinos and their detection in a satellite-based experiment

The ultra-high-energy (UHE) atmospheric showers with strong influence of the Landau-Pomeranchuk-Migdal (LPM) effect (here after LPM showers) are exclusively expected to be produced by UHE neutrinos. Studies on the characteristics of the LPM showers are essentially important to discriminate neutrino shower (which produced by neutrino interaction) from hadronic shower (initiated by primary hadron). We calculate the LPM showers initiated by electrons with energies of 10¹⁸ to 10²¹ eV, using the hybrid method as exactly as possible. Reflecting the change in the air density along the shower trajectories, the variety of the LPM-shower profiles is shown in different cases for their starting points in atmosphere. Through the study of time profiles of air fluorescent photon components from the LPM showers, the detection capability of UHE neutrinos has also been investigated by the satellite-based experiment with a large acceptance, e.g., the TUS experiment.     

Direct polyamidation with thionyl chloride in N-methyl-pyrrolidone

Mechanistic features of the reaction promoted by thionyl chloride and amides such as N-methylpyrrolidone (NMP) were studied. The reaction was effective in the amidation of carboxylic acids, but not effective in the esterification. The amidation was affected by the kind and the amount of amides used, most favorably by two equivalents of NMP with respect to the acid. These amides were assumed to be involved in the intermediate formation, and the reaction was proposed to proceed via Vilsmeier adducts derived from thionyl chloride and the amides, and through activation of a carboxylic acid different from an acyl chloride. The reaction was successfully applied to the direct polycondensation of aromatic dicarboxylic acids and diamines in NMP at 70°C to produce polyamides with high molecular weights. Initial reaction of dicarboxylic acids with the adducts, additive effect of tertiary amines, and polycondensation temperatures were studied in terms of the inherent viscosity of the polymers produced.     

Direct polycondensation with tosyl chloride in pyridine by formamide catalyzed alcoholysis

The reaction with tosyl chloride was significantly promoted by controlling alcoholysis with bisphenols in the presence of catalytic amounts of formamides to give aromatic polyesters with high molecular weights from aromatic dicarboxylic acids and bisphenols. Mechanistic features of the reaction were studied by use of various formamides and other arylsulfonyl chlorides, as well as by varying the addition mode of bisphenols and changing the relative amount of formamide. The reaction was successfully applied to the preparation of aromatic polyesteramides with high molecular weights from aromatic dicarboxylic acids, bisphenols, and diamines, but with limited success to that of polyamides.