New polymer syntheses XCIII. Hyperbranched homo- and copolyesters derived from gallic acid and β-(4-hydroxyphenyl)-propionic acid

The hyperbranched homopolyester of gallic acid (GA) was prepared by polycondensation of acetylated gallic acid in bulk. Copolyesters of gallic acid and 3-hydroxybenzoic acid (3-HBA) or β-(4-hydroxyphenyl)propionic acid (HPPA) were prepared via the silylated monomers. The degree of branching was varied in both series via the molar fraction of gallic acid. A model reaction with silylated 4-methoxybenzoic acid suggests that all three acetoxy groups of gallic acid can react by ester interchange reactions under the chosen reaction conditions. Furthermore, highly branched copolyesters derived from equimolar ratios of HPPA and 2-, 3-, or 4-hydroxybenzoic acid, vanillic acid, or 4-hydroxycinnamic acid were synthesized. All these copolyesters were found to be amorphous with glass transition temperatures (T_g's) far below that of the hyperbranched poly(gallic acid). © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2347–2357, 1998     

New polymer syntheses. XCVI. Star-shaped LC-polyesters derived from β-(4-hydroxyphenyl)propionic acid and 4-hydroxybenzoic acid

Star-shaped polyesters were prepared by polycondensation of tetraacetoxyspirobis(indane) and a 1 : 1 mixture of silylated β-(4-acetoxyphenyl)propionic acid and silylated 4-acetoxybenzoic acid. The lengths of the star arms were systematically varied, and the influence of the star center on the stability of the nematic phase was studied. It was found that on the average more than 10 monomer units per star arm are required to stabilize a homogeneous LC-phase. Furthermore, a second class of star-shaped polyesters consisting of β-(4-hydroxyphenyl)propionic acid (HPPA), 4-hydroxybenzoic acid (HBA), and 6-hydroxy-2-naphthoic acid (HNA) was prepared. This ternary copolyester proved to reduce the crystallinity but to stabilize the LC-character. A homogeneous nematic melt was obtained with 6 monomer units per star arm. This interpretation is based on optical microscopy which provides a static picture of the biphasic situation. Therefore, a preliminary study of the melt rheology was included, which proved that the typical LC-character of the melt was detectable ateven shorter star arms due to the shear orientation. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1387–1395, 1998     

Whiskers. VIII. A convenient synthesis of poly(4-hydroxybenzoate) whiskers and their application in composites of nylon-6

Whiskers of poly(4-hydroxybenzoate) [poly(4-HBA)] were prepared by polycondensation of free 4-hydroxybenzoic acid with acetic anhydride and pyridine in a high boiling inert solvent. The purity of the monomer is decisive for the success of the synthesis. For a less pure 4-hydroxybenzoic acid, the preparation of acetylated oligomers with acetylchloride, followed by polycondensation of the isolated oligomers is a suitable alternative. Whiskers, with a solid-solid phase transition at 364°C were obtained, which is the highest temperature reported for this transition so far. Two batches of composites were prepared from nylon-6 using polyester whiskers with an alkaline or an acidic surface treatment. A third batch was prepared using poly(ester-amide) whiskers. The mechanical properties of these composites indicate that the surface treatment does not play any role, and that the poly(esteramide)s are inferior to the polyester whiskers, because they are not single crystals. © 1994 John Wiley & Sons, Inc.     

New polymer syntheses. LXVI. Copolyester of 4-hydroxybenzoic acid and 3-(4'-hydroxyphenoxy)benzoic acid or 4-(3'-hydroxyphenoxy)benzoic acid

Copolyesters of 4-hydroxybenzoic acid (HBA) and 3-(4'-hydroxyphenoxy)benzoic acid were prepared by two different procedures. Either the acetyl derivatives were polycondensed in bulk at temperatures up to 300°C or they were polycondensed in an inert reactions medium (Marlotherm-S) at 340°C. Two analogous series of copolyesters were synthesized from 4-acetoxybenzoic acid (4-HBA) and 4-(3'-acetoxyphenoxy)benzoic acid. The copolyesters were characterized by elemental analyses, inherent viscosities, ¹H- and ¹³C-NMR spectroscopy, WAXS and DSC measurements, and by optical microscopy. All copolyesters synthesized in solution were highly crystalline materials which were neither meltable nor soluble. Part of the copolyesters prepared by polycondensation in bulk were semi-crystalline, meltable, and soluble. The copolyester derived from 3-(4'-hydroxyphenoxy)benzoic acid proved to be thermotropic forming a nematic melt, whereas the isomeric copolyesters of 4-(3'-hydroxyphenoxy)benzoic acid only formed isotropic melts. © 1993 John Wiley & Sons, Inc.     

(R)-2-硫代四氢噻唑-4-羧酸及其酯的合成

L-半胱氨酸盐酸盐与二硫化碳, 氢氧化钠在硝酸铅存在下进行成环反应得到(R)-四氢噻唑-2-硫酮-4-羧酸产率76% , 后者与 醇在硫酸铁水合物催化下反应得到(R)-四氢噻唑-2-硫酮-4-羧酸酯, 产率40～82% .     

New polymer syntheses. 60. Thermostable polymers of 2-(hydroxyaryl)benzoxazole-5-carboxylic acids

Tristrimethylsilyl-3-amino-4-hydroxybenzoic acid was condensed with various aromatic acetoxy carboxylic acid chlorides in Marlotherms-S® at 20–350°C. Under these conditions formation of an amide group, ring closure to benzoxazole groups and polycondensation occur step by step in a “one-pot procedure”. The crude polyesters were hydrolyzed to yield pure 2-(hydroxyaryl) benzoxazole-5-carboxylic acids which were acetylated and polycondensed. The pure polyesters obtained in this way were characterized by viscosity and DSC measurements, WAXS-powder patterns, and thermogravimetric analyses. The polyester of 2-(4-hydrophenyl) benzoxazole-5-carboxylic acid has a degree of crystallinity > 90% and a short term in thermostability in air up to 500°C.     

New polymer syntheses. XC. A–B–A triblock copolymers with hyperbranched polyester A-blocks

Telechelic oligo(ether–ketone)s containing two trimethylsiloxy end groups and one methyl group per repeating unit were prepared by polycondensation of 4-fluoro-2′-methyl-4′-(trimethylsiloxy)benzophenone. The telechelic character was achieved by cocondensation of a small amount of silylated bisphenol-P. The end groups of the silylated oligo(ether–ketone)s were acetylated by means of acetyl chloride. On the basis of ¹H-NMR end group analyses two samples of α,ω-bis(acetoxy) oligo(ether–ketone)s with DP = 14 and DP ∼ 28 were obtained. These oligo(ether-ketone)s and a 70 or 140 fold molar amount of silylated 3,5-bis(acetoxy)benzoic acid were polycondensed at 270°C in bulk. The resulting A–B–A triblock copolymers were fractionated by dissolution in tetrahydrofuran. In three out of four experiments a small fraction of precipitated material rich in oligo(ether–ketone) was isolated. The purified triblock copolymers were characterized by inherent viscosities and NMR spectra. For those samples containing the long oligo(ether–ketone) block a low degree of crystallinity was observed after annealing. Four additional polycondensations were conducted with an initial reaction temperature of 290°C. In this way a completely soluble and amorphous triblock copolymer was obtained. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 31–38, 1998     

Preparation and characterization of molecularly imprinted monolithic column based on 4-hydroxybenzoic acid for the molecular recognition in capillary electrochromatography

A novel prepared method of molecularly imprinted monolithic polymers (MIPs) using 4-hydroxybenzoic acid (4-HBA) as templates for capillary electrochromatography (CEC) was developed. A strategy of high concentration of monomers in the pre-polymerization mixture was used to fulfil the solubility of polar imprinted molecule and reduction of the interference during complex formation. The imprinted polymer capillary monolithic column was synthesized by an in situ therm-initiated copolymerization of methacrylic acid (MAA) and ethylene glycol dimethacrylate with a mixture of toluene-isooctane as a porogenic solvent in the presence of a polar model imprinting molecule, 4-HBA. On the resultant MIP monolithic column, the effect of parameter of CEC on electroosmotic flow (EOF) and the retention of 4-HBA was investigated. The column efficiency of the imprinted molecule, 4-HBA, was 13,000 plates/m. The resolution of isomers of HBA was 5.0 and good molecular recognition was achieved for 4-HBA.     

Polycyclic nitrogen compounds. Part II. Tricyclic quinoxalinones and their 4- or 6-aza analogues

1,2,3,3a-Tetrahydro-9-nitropyrrolo[1,2-α]quinoxalin-4-one and 7,8,9,10-tetrahydro-3-nitropyrido[1,2-α]quin-oxalin-6-one (V-VI) were reduced and deaminated to give new parent tricyclic quinoxalinone skeletons I-II. The latter compounds were identical with the tricycles obtained by an unambiguous independent synthesis. New 6-aza-1,2,3,3a-tetrahydropyrrolo[1,2-α]quinoxalin-4-one (III) and 4-aza-7,8,9,10-tetrahydropyrido[1,2-α]-quinoxalin-6-one (IV) were prepared by selective hydrogen transfer reductive cyclisation of esters of N-(2-nitro-3-pyridyl)pyrrolidine-2-carboxylic acid and N-(2-nitro-3-pyridyl)piperidine-2-carboxylic acid (Xb and XIb) respectively.     

New polymer synthesis. LXXXIII. Synthesis of chiral and cholesteric polyesters from silylated “sugar diols”

A series of polycondensation was conducted with the purpose to optimize the reaction conditions for the polycondensation of silylated 2,3-isopropylidene D -threitol with a dicarboxylic acid dichloride. Polycondensation in o-dichlorobenzene or 1-chloronaphthalene at 180–230°C were found to be most satisfactory. Trifluoroacetic acid/H₂O allow an easy cleavage of the isopropylidene group without hydrolysis of the polyester. Ten cholesteric copolyesters were prepared by polycondensation of mixtures of silylated methylhydroquinone and isosorbide, isomannide, or 2,3-isopropylidene threitol with the dichloride of 1,10-bis(4′-carboxyphenoxy)decane. All these copolyesters form a broad cholesteric phase above 200°C. The copolyesters containing 5 or 10 mol % of a sugar diol display a blue Grandjean texture. © 1996 John Wiley & Sons, Inc.     

Synthesis of 4H-1,4-benzothiazine 1-oxide and 1,1-dioxide. Analogs of quinolone antibacterial agents

4-Cyclopropyl-5,7-difluoro-6-(4-methyl-1-piperazinyl)-4H-1,4-benzothiazine-2-carboxylic acid 1-oxide (2c) and 4-cyclopropyl-5,7-difluoro-6-(4-methyl-1-piperazinyl)-4H-1,4-benzothiazine-2-carboxylic acid 1,1-dioxide (2d) were prepared and assayed for antibacterial activity and inhibition of DNA gyrase.     

6-氟-色满-2-羧酸的合成及其(R)-, (S)-光学异构体的拆分研究

以对氟苯酚为起始原料合成了6-氟-4-色满酮-2-羧酸, 该中间体经催化还原获得了消旋的6-氟-色满-2-羧酸. 化学拆分该消旋体和D-(＋)-α-苯乙胺及L-(－)-α-苯乙胺形成的非对映体盐, 分别得到了(R)-及(S)-6-氟-色满-2-羧酸.     

Synthesis of aromatic polyamide-imides from N,N′-bis(trimethylsilyl)-substituted aromatic diamines and 4-chloroformylphthalic anhydride

The polymerization of N,N′-bis(trimethylsilyl)-substituted aromatic diamines with 4-chloroformylphthalic anhydride in various solvents at a temperature range between 10 and 70°C afforded polyamide-amic acid trimethylsilyl esters having inherent viscosities of 0.8–1.4 dL/g. Transparent and flexible films of the silylated precursor polymers were obtained by casting directly from the polymer solutions. Desilylation of the silylated polymers with methanol resulted in the formation of the corresponding polyamide-amic acids. Subsequent thermal imidization of the silylated precursor polymers with the elimination of trimethylsilanol afforded yellow, transparent, and tough films of the aromatic polyamide-imides. The thermal conversion of the silylated precursor polymer to polyamide-imide proceeded almost as rapidly as that of the corresponding polyamide-amic acid prepared by a conventional method from the parent aromatic diamine and 4-chloroformylphthalic anhydride.     

1,6- and 1,7-naphthyridines. II. Synthesis from acyclic precursors

A number of 8-hydroxy-6-methyl-1,6-naphthyridin-5(6H)-one-7-carboxylic acid alkyl esters 3 and the isomeric 5-hydroxy-7-methyl-1,7-naphthyridin-8(7H)-one-6-carboxylic acid alkyl esters 4 were synthesized from acyclic precursors obtained starting from quinolinic anhydride 5. Thus, methanolysis of 5 afforded the hemiester 6 which treated with oxalyl chloride and sarcosine ethyl ester gave 3-(N-ethoxycarbonylmethyl-N-methylcarbamoyl)pyridine-2-carboxylic acid methyl ester 8. Compound 8 was cyclized to naphthyridines 3a-e with sodium alkoxides. The isomeric naphthyridines 4a-c were obtained by cyclization of the open intermediary 2-(N-ethoxycarbonylmethyl-N-methylcarbamoyl)pyridine-3-carboxylic acid methyl ester 9 obtained by a route that involves treatment of 5 with sarcosine ethyl ester and esterification with diazomethane. Spectroscopic properties (¹H nmr, uv, ir) of compounds 3 and 4 are discussed and confirmed the proposed structures.     

New polymer syntheses. CIX. Biodegradable,alternating copolyesters of terephthalic acid,aliphatic dicarboxylic acids,and alkane diols

Copolyesters with an alternating sequence of terephthalic acid and aliphatic dicarboxylic acids were prepared with three different methods. First, dicarboxylic acid dichlorides were reacted with bis(2‐hydroxyethyl)terephthalate (BHET) in refluxing 1,2‐dichlorobenzene. Second, the same monomers were polycondensed at 0–20 °C in the presence of pyridine. Third, dicarboxylic acid dichlorides and silylated BHET were polycondensed in bulk. Only this third method gave satisfactory molecular weights. Matrix‐assisted laser desorption/ionization time‐of‐flight mass spectrometry revealed that the copolyesters prepared by the pyridine and silyl methods might have contained considerable fractions of cyclic oligoesters and polyesters despite the absence of transesterification and backbiting processes. The alternating sequences and thermal properties were characterized with ¹H NMR spectroscopy and differential scanning calorimetry measurements, respectively. In agreement with the alternating sequence, all copolyesters proved to be crystalline, but the crystallization was extremely slow [slower than that of poly(ethylene terephthalate)]. A second series of alternating copolyesters was prepared by the polycondensation of silylated bis(4‐hydroxybut‐ yl)terephthalate with various aliphatic dicarboxylic acid dichlorides. The resulting copolyesters showed significantly higher rates of crystallization, and the melting temperatures were higher than those of the BHET‐based copolyesters. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3371–3382, 2001     

Synthetic antibacterials. VIII. 7-(1′-alkylhydrazino)-1,8-naphthyridines and related compounds

Synthesis and in vitro antibacterial activity of 7-(1′-alkylhydrazino)-1,8-naphthyridines related to nalidixic acid were investigated. Namely, treatment of 7-alkylamino-1-ethyl-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylic acids 1a-d with sodium nitrite in the presence of hydrochloric acid gave the 1-ethyl-1,4-dihydro-7-(N-nitrosoalkylamino)-4-oxo-1,8-naphthyridine-3-carboxylic acids 2a-d , which upon reacting with zinc dust in acetic acid gave the 7-(1′-alkylhydrazino)-1-ethyl-1,4-dihydro-4-oxo-1,8-naphthyridine-3-carboxylicacids 3a-d. The compound 3a was alternately obtained by the reaction of 7-chloro-1-ethyl-1,4-dihydro-4-oxo-1,8-naphth-yridine-3-carboxylic acid ( 4 ) with methylhydrazine. The reaction of 7-chloro-4-hydroxy-1,8-naphthyridine-3-carboxylic acid ( 5 ) with methylhydrazine gave the 4-hydroxy-7-(1′-methylhydrazino)-4-oxo-1,8-naphthyridine-3-carboxylic acid ( 6 ), which upon treatment with alkyl halides afforded the 1-alkyl-1,4-dihydro-7-(1′-methyl-hydrazino)-4-oxo-1,8-naphthyridines 3a and 3e-g. The reaction of the appropriate 3 with ketones gave the corresponding 7-(1′-methylalkylidenehydrazino)-1,8-naphthyridines 7a-c and 8a-b. Among the compounds prepared, certain 3 and 7 exhibited good activity against Gram-negative bacteria.     

Identification of two aromatic isomers between 3- and 4-hydroxy benzoic acid by their perturbation on the potential oscillations of a Belousov-Zhabotinsky system

A novel method for identification of two aromatic isomers of mono hydroxy benzoic acid (HBA) was reported by using their different perturbation effects on the potential oscillations of a Belousov-Zhabotinsky (BZ) system. In such a system, a macrocyclic complex of Cu [CuL](ClO₄)₂ was used as catalyst in which ligand L is 5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene. To the BZ system, 3-hydroxy benzoic acid (3-HBA) could temporarily quench and regenerate potential oscillations with damping characters after inhibition time (t_in) while 4-hydroxy benzoic acid (4-HBA) could only change the oscillation amplitude (ΔA) to give damping oscillations with no inhibition time. Thus, these two isomers of HBA were identified. Reaction mechanisms of BZ have been proposed by FKN model. An explanation of perturbation mechanism is that, although 3-HBA reacted with BrO₂ while 4-HBA reacted with BrO₃⁻, they all produced 1,4-quinone.     

Lipase-mediated kinetic resolution of rigid clofibrate analogues with lipid-modifying activity

The lipase-catalysed kinetic resolution of methyl esters of (±)-5-chloro-2,3-dihydro-1-benzofuran-2-carboxylic acid, (±)-6-chloro-2,3-dihydro-4H-1-benzopyran-2-carboxylic acid, and (±)-6-chloro-2,3-dihydro-4H-1-benzopyran-3-carboxylic acid, rigid analogues of clofibrate, was effected with fair to moderate enantioselectivities (E=1.0–4.8), enantiomeric excesses of up to 86% and workable reaction rates. Enantiomerically pure (R)- and (S)-5-chloro-2,3-dihydro-1-benzofuran-2-carboxylic acids were obtained by fractional crystallisation of the diastereomeric salts of the corresponding racemic acid with (+)- and (−)-amphetamine from ethanol; the absolute configuration of the products were established by chemical correlation.     

Methylmercury(II) complexes with 2-mercaptopyridinecarboxylic acids

The stability constants of the complexes [MeHgL]^?(H₂L = 2-mercaptopyridine-3-carboxylic acid, 2-mercaptopyridine-4-carboxylic acid, 2-mercaptopyridine-5-carboxylic acid and 2-mercaptopyridine-6-carboxylic acid) have been obtained by differential pulse polarography. The values of log β₁ are in the range 14.14–14.96 at 20°C and ionic strength 0.1 mol dm^?3. The complexes MeHgHL have been isolated and characterized by chemical analysis and mass and IR spectrometry.     

Synthesis,spectral properties,in vitro α-glucosidase inhibitory activity and quantum chemical calculations of novel mixed-ligand M(II) complexes containing 1,10-phenanthroline

A series of mixed-ligand M(II) complexes containing 1,10-phenanthroline (phen) and 3-methylpyridine-2-carboxylic acid (3-mpaH) or 6-methylpyridine-2-carboxylic acid (6-mpaH), namely [Co(3-mpa)₂(phen)]·3H₂O ( 1 ), [Hg(6-mpa)₂(phen)]·2H₂O ( 2 ), [Mn(6-mpa)₂(phen)]·2H₂O ( 3 ), [Co(6-mpa)₂(phen)]·H₂O ( 4 ) and [Ni(6-mpa)₂(phen)]·H₂O ( 5 ), were synthesized for the first time. Among them, 1 was obtained as single crystals. The structural characterization for 1 was conducted using X-ray diffraction and that for 2 – 5 using mass spectrometry. The IC₅₀ values for α-glucosidase inhibition of 1 – 5 were obtained as 0.161 to >600 μM. The spectral properties were also investigated using Fourier transform infrared and UV–visible spectra. Furthermore, to investigate the geometrical parameters, spectral and electronic properties and second- and third-order nonlinear optical parameters for 1 – 5 , density functional calculations were applied.