Anhydrous Potassium Carbonate Research Articles

Potassium carbonate–silica: a highly effective stationary phase for the chromatographic removal of organotin impurities

Organotin impurities in product mixtures can be reduced from stoichiometric levels to approximately 15 parts per million by column chromatography using 10% w/w anhydrous potassium carbonate-silica as a stationary phase.

Synthesis, DNA Binding, and Antimicrobial Activity of Base-Catalyzed 2-Phenyl-3-pyrido[3,2][1,3,4]thiadiazolo [3,2]quinoline Derivatives

A series of novel 3-{[(5-phenyl-1,3,4-thiadiazol-2-yl)imino] methyl}quinoline-2-thione (2a–c) and 2-phenyl-3-pyrido[3,2][1,3,4]thiadiazolo[3,2]quinoline derivatives (3a–c) were prepared by a facile synthetic method using an anhydrous potassium carbonate catalyst. The newly synthesized heterocyles were characterized by elemental analysis, FT-IR, 1H-NMR, and mass spectral data. The selected compounds were studied for interaction with calf thymus-DNA(CT-DNA) by electronic spectra and viscosity measurements, as well as thermal denaturation studies. Upon binding to DNA, the absorption spectrum underwent bathochromic and hypochromic shifts. The binding constant (Kb) observed value of 8.4 × 105 M−1 for (2a) and 8.2 × 105 M−1 for (3a) suggested that compound (2a) binds more avidly to CT-DNA than compound (3a). The increasing viscosity of sonicated rod-like DNA fragments and the melting temperature of DNA, in the presence of compound solutions, support the binding mode. The synthesized derivatives have been screened for antibacterial and antifungal activities.

CC bond formation by radical cyclization: Facile syntheses of [6,6]pyranothiopyrans and [6,6]pyridothiopyrans

Abstract magnified image 4‐Chloromethylthiopyrano[3,2‐c][1]benzopyran‐5‐(2H)‐ones were refluxed with o‐bromophenols in acetone in the presence of anhydrous potassium carbonate and sodium iodide to afford a number of 4‐aryloxymethylthiopyrano[3,2‐c][1]benzopyan‐5‐(2H)‐ones in 72–79% yields. These compounds were refluxed with tri‐n‐butyltin hydride and azobisisobutyronitrile in dry benzene for 7–8 h to give [6,6]pyranothiopyrans in 76–84% yields with good diastereoselectivity. Similarly, [6,6]pyridothiopyrans were also synthesized in 70–75% yields with excellent diastereoselectivity. J. Heterocyclic Chem., (2009).

New pyridone, thioxopyridine, pyrazolopyridine and pyridine derivatives that modulate inflammatory mediators in stimulated RAW 264.7 murine macrophage

The reaction of 2-acetyl-5,6,7,8-tetrahydronaphthalene 1 with some aldehydes was conducted in the presence of ethyl cyanoacetate and ammonium acetate, yielded the cyanopyridones 2a– c, which react with phosphorous pentasulphide to afford the corresponding thioxopyridine derivatives 3a– c, respectively. Compounds 2a, b were converted to 2-chloropyridine derivatives 4a, b by heating with phosphorous oxychloride and phosphorous pentachloride, which were fused with hydrazine hydrate and benzyl amine to afford the corresponding pyrazolopyridine 5a, b and cyanopyridine derivatives 6a, b respectively. Compounds 2a, b also afforded 3-cyanopyridinyl oxy acetic acid ethyl ester 7a, b by reaction with ethyl bromoacetate in dry acetone in the presence of anhydrous potassium carbonate, which upon condensation with hydrazine hydrate gave the corresponding acid hydrazide 8a, b and with benzyl amine gave the corresponding acetamide 9a, b. We investigated the effect of those new compounds on the macrophage growth, macrophage binding affinity to fluorescein isothiocyanate-conjugated bacterial lipoopolysaccharide (FITC-LPS), phagocytosis of FITC-zymosan, and radical scavenging affinity against OH , ROO , and O 2 − , in addition to their influence of the inflammatory mediators [nitric oxide (NO), tumor necrosis factor-α (TNF-α), prostaglandin E-2 (PGE-2), cycloxygenase-2 (COX-2), and 5-lipoxygenase (5-LO)] in LPS-stimulated macrophages. The findings revealed that the derivatives 2b, 3b, 5a, 7b, 9a and 9b can be recognized as promising multi-potent anti-inflammatory agents.

Synthesis and characterization of novel soluble cardo poly(arylene ether ketone)s containing xanthene structures

Abstract9,9‐Bis(4‐hydroxyphenyl)xanthene (BHPX), a bisphenol monomer, was synthesized in 82% yield from xanthenone in a one‐pot, two‐step synthetic procedure. Four novel aromatic poly(ether ketone)s (PEKs) based on BHPX were prepared via a nucleophilic aromatic substitution polycondensation with four difluorinated aromatic ketones. The polycondensation proceeded in tetramethylene sulfone in the presence of anhydrous potassium carbonate and afforded the new cardo PEKs in nearly quantitative yields with inherent viscosities of 0.77–0.85 dL/g. High molecular weight PEKs having number‐average molecular weights (Mn's) in the range of 38,900–40,600 g/mol with the polydispersity index ranged from 1.97 to 2.06 are all amorphous and show high glass transition temperatures ranging from 210°C to 254°C, excellent thermal stability, and the temperatures at the 5% weight loss are over 538°C with char yields above 60% at 700°C in nitrogen. These new PEKs are all soluble in polar aprotic solvents such as N‐methyl‐2‐pyrrolidone and N, N′‐dimethylacetamide and could also be dissolved in chloroform and tetrahydrofuran. All the polymers formed transparent, strong, and flexible films with tensile strengths of 78–84 MPa, Young's moduli of 2.54–3.10 GPa, and elongations at break of 14–18 %. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Synthesis and characterization of a novel photocrosslinkable fluorinated poly(arylene ether) for optical waveguide

To improve its chemical resistance and mechanical stability, a novel fluorinated poly(arylene ether) bearing a photocrosslinkable chalcone group in the main chain was successfully synthesized by means of polycondensation between 4,4′-dihydroxychalcone and decafluorobiphenyl in N,N-dimethylacetamide in the presence of the excess anhydrous potassium carbonate. The structure of polymer was characterized by 1H NMR and 19F NMR spectroscopies. The resulting polymer shows excellent solubility in common organic solvents, high glass transition temperature and good thermal stability. Crosslinking of the resulted polymer has been demonstrated by UV irradiation. Near-IR spectra of polymer film before and after UV irradiation show no absorption at the telecommunication wavelengths of 1310 and 1550 nm, demonstrating that the resulting polymer is good candidate material for optical waveguide application.

6- exo versus 7- endo iodolactonizations of 2-(alkynyl)phenylacetic acids

Exposure of 2-alkynylphenylacetic acids to excess iodine in acetonitrile containing anhydrous potassium carbonate delivers good yields, either of the corresponding isochroman-3-ones or benzo[ d]oxepin-2(1 H)-ones, depending upon the alkyne substituent: when this is alkyl, the former 6- exo products dominate, otherwise the 7- endo products are formed largely or, more often, exclusively.

Synthesis and characterization of 2, 5-disubstituted-1, 3, 4-oxadiazoles as potential anti-inflammatory agents

The aim of this study was to design, synthesize, and investigate the in vivo anti-ins ammatory activity of some novel 2, 5-disubstituted - 1, 3, 4-oxadiazole derivatives. Ethyl-4-acetamido phenoxy acetate (I) was prepared by the condensation of ethyl chloroacetate with starting material p-acetamidophenol in the presence of dry acetone and anhydrous potassium carbonate. Hydrazinolysis of (I) with hydrazine hydrate results in the formation of 4-acetamidophenoxy acetyl hydrazide (II), which on cyclisation with various substituted aromatic carboxylic acids in the presence of phosphorous oxychloride affords various 2, 5-disubstituted - 1, 3, 4-oxadiazole derivatives (IIIa-IIIi). The newly synthesized compounds were characterized by IR, 1HNMR, and MS spectral data. The titled compounds were screened for in vivo anti- ins ammatory activity using the carrageenan-induced paw edema method. A few of them manifested promising activity when compared with the standard drug Diclofenac sodium. Key words: Anti-ins ammatory activity, 1, 3, 4 - oxadiazoles, Ethyl - 4- acetamido phenoxy acetate, 4 - acetamido phenoxy acetyl hydrazide.

5-Aminouracil as a Building Block in Heterocyclic Synthesis: Part I. One-pot Synthesis of Pyrimido[5,4-b]quinolin-2,4,9-triones under Microwave Irradiation without Catalyst

A series of 6,7,8,10-tetrahydropyrimido[5,4-b]quinolin-2,4,9-(1H,3H,5H)-triones 6 were synthesized through one-pot condensation of 5-aminouracil, aldehydes and dimedone in DMF under microwave irradiation without catalyst. The products 6a, d were oxidized to the 7,8-dihydro-pyrimido- [5,4-b]quinolin-2,4,9-(1H,3H,6H)-triones 11a, b. Treatment of 6a, d and/or 11a, b with ethyl iodide in the presence of anhydrous potassium carbonate gave the ethylated derivatives 12a, b and 13a, b, respectively. The structures of the products were confirmed by elemental analyses, IR, MS, 1H, and 13C NMR spectra.

Regioselective Synthesis of 1,8-Naphthyridinone-Annulated Oxygen and Sulfur Heterocycles by Tri-n-butyl Tinhydride–Mediated Aryl Radical Cyclization

The tin hydride–mediated cyclizations of a number of ethers, sulfides, and sulfones under mild, neutral conditions have been investigated. While the 2-bromobenzyloxy ethers were prepared in 62–65% yields by the alkylation of 4-hydroxy-1-phenyl-1,8-naphthyridin-2(1H)-one with 2-bromobenzyl bromides in refluxing acetone in the presence of anhydrous potassium carbonate, the sulfides were derived from 4-mercapto-1-phenyl-1,8-naphthyridin-2(1H)-one and 2-bromobenzyl bromides in 82–84% yields by a phase-transfer catalysis (PTC) reaction. The corresponding sulfones were prepared by treatment of the sulfides with m-CPBA in refluxing dichloromethane. The ethers, sulfides, and the sulfones were treated with n Bu3SnH-AIBN to give regioselectively 1,8-naphthyridinone-annulated oxygen and sulfur heterocycles in 70–78% yields.

High glass transitions and fluorescence of novel organosoluble poly(arylene ether)s containing kink noncoplanar heterocyclic structures

A novel unsymmetrical and kink noncoplanar heterocyclic bisphenol-like monomer, 4-(4-hydroxynaphthalenyl)phthalazin-1-one (2), was synthesized in a two-step reaction starting from 1-naphthol and phthalic anhydride via Friedel-Crafts acylation reaction and cyclization with hydrazine hydrate. Two heterocyclic poly(arylene ether)s were prepared conveniently from monomer 2 and two activated dihalide monomers by a N-C coupling reaction. The polycondensation proceeded quantitatively in N,N-dimethylacetamide in the presence of anhydrous potassium carbonate and afford the polymers with inherent viscosities of 0.46 and 0.34 dL/g. Thermal analysis showed that the polymers had excellent thermal properties. The glass transition temperatures were 277 °C and 316 °C respectively, and the temperatures of 5% weight loss were all above 500 °C in nitrogen atmosphere. The unsymmetrical and kink noncoplanar structures of the polymers chains could disturb interchain and intrachain interactions and make them amorphous and readily soluble in polar, aprotic solvents. The dilute solution of the polymers in chloroform showed strong optical absorption in ultraviolet region, and exhibited violet-blue fluorescence with emission maxima at 400-470 nm.

Synthesis of poly(ether ether ketone) assisted by microwave irradiation and its characterization

Poly(ether ether ketone) (PEEK) was synthesized with a good yield, by nucleophilic substitution reaction of 4,4’-difluorobenzophenone (DFBP) with hydroquinone (HQ) in the presence of anhydrous potassium carbonate (K2CO3) under microwave (MW) irradiation. The highest yield of 96.1% was obtained using sulfolane as the solvent and with a reaction time of only 55 min. The reaction time was reduced greatly compared with conventional heating. The product was characterised by infrared spectroscopy (IR), X-ray diffraction (XRD), thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The polymer, having inherent viscosities of 0.71 dlg-1, has excellent thermal stability as shown by 10% weight loss in nitrogen at about 563 °C. The XRD pattern confirmed the semicrystalline character of PEEK synthesized.

Synthesis and antimicrobial activity of imidazo- and pyrimido[2,1-f]-theophyllines

Heating of 8-aminotheophylline with methyl (Z)-2-benzoylamino-3-(dimethylamino)propenoate in acetic acid afforded in a one-pot synthesis a new pyrimido(2,1-f)theophylline derivative. Methylation of this by using CH3I=NaH furnished in good yield the double methylated derivative. Furthermore, glyco- sidation of the former with 1-� -bromo-2,3,4,6-tetra- O-acetyl-D-glucose gave the � -glucoside derivative. Reaction of 8-aminotheophylline with (bis(methyl- thio)methylene)malonitrile, ethyl(bis(methylthio)- methylene)cyanoacetate, 1,3-diphenylprop-2-en-1-one, 2-cyano-1,3-diphenylprop-2-en-1-one, 1-(4-nitrophe- nyl)-3-(dimethylamino)prop-2-ennitrile, 1-phenyl-3- (dimethylamino)prop-2-en-1-one, 2-substituted 3-aryl or heteroarylprop-2-ennitrile and ethyl(arylmethyl- ene)cyanoacetate in N,N-dimethylformamide in the presence of anhydrous potassium carbonate afforded also the corresponding new derivatives of pyrimido- (2,1-f)theophylline. However, 8-aminotheophylline reacted in similar manner with 3-chloropentan-2,4- dione and 2-bromo-1-phenylethanone to give the cor- responding imidazo(2,1-f)theophyllines. Furthermore, azo-coupling of one of these with 4-methylphenyldia- zonium chloride was performed. The antimicrobial activity of the products has been evaluated. The struc- tures of all new compounds obtained were established by their spectral analyses.

1,3-Bis(ethylamino)-2-nitrobenzene, 1,3-bis(n-octylamino)-2-nitrobenzene and 4-ethylamino-2-methyl-1H-benzimidazole

1,3-Bis(ethylamino)-2-nitrobenzene, C(10)H(15)N(3)O(2), (I), and 1,3-bis(n-octylamino)-2-nitrobenzene, C(22)H(39)N(3)O(2), (II), are the first structurally characterized 1,3-bis(n-alkylamino)-2-nitrobenzenes. Both molecules are bisected though the nitro N atom and the 2-C and 5-C atoms of the ring by twofold rotation axes. Both display intramolecular N-H...O hydrogen bonds between the amine and nitro groups, but no intermolecular hydrogen bonding. The nearly planar molecules pack into flat layers ca 3.4 A apart that interact by hydrophobic interactions involving the n-alkyl groups rather than by pi-pi interactions between the rings. The intra- and intermolecular interactions in these molecules are of interest in understanding the physical properties of polymers made from them. Upon heating in the presence of anhydrous potassium carbonate in dimethylacetamide, (I) and (II) cyclize with formal loss of hydrogen peroxide to form substituted benzimidazoles. Thus, 4-ethylamino-2-methyl-1H-benzimidazole, C(10)H(13)N(3), (III), was obtained from (I) under these reaction conditions. Compound (III) contains two independent molecules with no imposed internal symmetry. The molecules are linked into chains via N-H...N hydrogen bonds involving the imidazole rings, while the ethylamino groups do not participate in any hydrogen bonding. This is the first reported structure of a benzimidazole derivative with 4-amino and 2-alkyl substituents.

Synthesis and drug release properties of poly(ethylene oxide) segmented polysulfone copolymers

A series of poly(ethylene oxide) (PEO) segmented polysulfone copolymers with different PEO content has been successfully synthesized via condensation polymerization of 4,4′-dichlorodiphenylsulfone (DCDPS), chlorine-end-capped poly(ethylene oxide) (PEO-Cl 2)) and 4,4′-dihydroxybiphenyl (DHBP) in N, N-dimethylacetamide (DMAc) in the presence of anhydrous potassium carbonate at 160 °C for 20 h. The resulting copolymers showed high molecular weights (Mn = 28,000–40,200 Da) and relatively narrow molecular weight distributions (Mw/Mn = 1.57–1.87). They are well soluble in common organic solvents such as chloroform and tetrahydrofuran. Films with high tensile strength (38–50 MPa) and good elasticity of elongation (elongation at break: 190–430%) were prepared by solution cast from the copolymer solutions in chloroform. Sirolimus and paclitaxel were used as drugs and their release kinetics were investigated. For both drugs, the release rate was strongly influenced by the PEO content of the polymer films, i.e., PSF–PEO films with higher PEO content showed larger drug release rate. Film swelling due to liquid sorption is mainly responsible for the drug release.

Mono-Brominated-Propyphenazone as a New Derivatization Reagent for High Performance Liquid Chromatography of Ephedrine with UV-Detection

mono-brominated-propyphenazone was used as a derivatization reagent for the detection and quantification of ephedrine by high performance liquid chromatography using Zorbax-XDB C18 column, and 0.02 M sodium acetate (pH 4.4): acetonitrile (52:48 v/v) as mobile phase and UV detection at 280nm. The cited reagent reacts with the secondary amino group of ephedrine in acetone using anhydrous potassium carbonate as hydrobromide acceptor. The reaction was completed within 20 minutes in 100 µL acetone with heating at 90 ± 5°C in a capped mini reaction vial. The stoichiometry of the reaction was one-to-one mol from each mono-brominated-propyphenazone and ephedrine. The linear concentration range of ephedrine was 30 to 900 ng per injection (50 µL). The detection limit was 9 ng/injection (50 µL). The derivatized ephedrine was synthesized and confirmed with spectral analysis. This method was applied for determination of spiked ephedrine in human urine and after extraction with charcoal column using methanol: 0.2 M NaOH (20:0.2, mL:mL) as eluant.

Synthesis, Crystal Structure and Thermal Properties of Phosphorylated Cyclotriphosphazenes

AbstractA convergent approach for the incorporation of arylphosphonate moieties into the cyclotriphosphazene unit is described. The synthesis is based on the reaction of hexachlorocyclotriphosphazene with diethyl 4‐hydroxyphenylphosphonate in the presence of anhydrous potassium carbonate. This reaction is characterised by substitution of the chloride atoms, which thus produces the hexaarylphosphono derivative in good yield. The product of this reaction is fully characterised, including a single X‐ray diffraction study. The hydrolysis of the hexaphosphonate compound to its hexaphosphonic acid analogue is reported. All products were characterised by NMR and IR spectroscopy and mass spectrometry. The thermal stability and degradation behaviour of these new compounds were investigated by thermogravimetric analysis.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

One‐Pot Solvent Free Synthesis and DNA Binding Studies of Thieno[2,3‐b]‐1,8‐Naphthyridines

With the aim of evaluating interaction between double‐stranded calf thymus (ds)DNA and sulphur containing fused planar rings, the derivatives of 1,8‐naphthyridine containing thiono groups were synthesized by the condensation of 2‐mercapto‐3‐formyl[1,8]naphthyridines using 1‐chloroacetone, 2‐chloroacetamide, chloroaceticacid, and 2‐chloro‐1‐phenylethanone in the presence of anhydrous potassium carbonate as s catalyst under solvent free microwave irradiation. The structures of the compounds were elucidated on the basis of elemental analysis, IR, 1H NMR, and mass spectra. The interaction of thieno[2,3‐b]‐1,8‐naphthyridine‐2‐carboxylic acid (TNC) (3a) with ct‐DNA was studied by UV‐Vis spectrophotometry, viscosity, thermal denaturation, as well as cyclic voltammetry experiments. On binding to DNA, the absorption spectrum underwent bathochromic and hypochromic shifts. Binding parameters, determined from spectrophotometric measurements indicated a binding constant of K b =2.1×106 M−1. The thieno[2,3‐b]‐1,8‐naphthyridine‐2‐carboxylic acid (3a) increases the viscosity of sonicated rod‐like DNA fragments. The binding of TNC to DNA increased the melting temperature by about 4°C. The decrease in peak current heights and shifts of peak potential values are observed by the addition of calf thymus DNA in cyclic voltammetry studies.

Toughening of an epoxy resin with hydroxy‐terminated poly(arylene ether nitrile) with pendent tertiary butyl groups

AbstractHydroxy‐terminated poly(arylene ether nitrile) oligomers with pendent tert‐butyl groups (PENTOH) were synthesized by the nucleophilic aromatic substitution reaction of 2,6‐dichlorobenzonitrile with tert‐butyl hydroquinone in N‐methyl‐2‐pyrrolidone medium with anhydrous potassium carbonate as a catalyst at 200°C in a nitrogen atmosphere. The PENTOH oligomers were blended with diglycidyl ether of bisphenol A epoxy resin and cured with 4,4′‐diaminodiphenyl sulfone. The curing reaction was monitored with infrared spectroscopy and differential scanning calorimetry. The morphology, fracture toughness, and thermomechanical properties of the blends were investigated. The scanning electron micrographs revealed a two‐phase morphology with a particulate structure of the PENTOH phase dispersed in the epoxy matrix, except for the epoxy resin modified with PENTOH with a number‐average molecular weight of approximately 4000. The storage modulus of the blends was higher than that of the neat epoxy resin. The crosslink density calculated from the storage modulus in the rubbery plateau region decreased with an increase in PENTOH in the blends. The fracture toughness increased more than twofold with the addition of PENTOH oligomers. The tensile strength of the blends increased marginally, whereas the flexural strength decreased marginally. The dispersed PENTOH initiated several toughening mechanisms, which improved the fracture toughness of the blends. The thermal stability of the epoxy resin was not affected by the addition of PENTOH to the epoxy resin. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Nano Composite Membranes of Branched Sulfonated Poly(Ether Ketone Sulfone) and SiO<sub>2</sub> for Fuel Cell Application

Branched sulfonated poly(ether ketone sulfone) copolymer was prepared from1,1,1- tris(4-hydroxyphenyl) ethane, 4,4-difluorophenylsulfone, 3,3'-disodiumsulfonylbenzophenone (40 mol% of bisphenol A) and bisphenol A by polycondensation with the elimination of water in toluene and NMP at 160) in the presence of anhydrous potassium carbonate. Composite membranes were successfully cast from the control of organic polymer with SiO2 4-10 wt% of polymer in DMSO. The films were converted from the salt to acid forms with dilute hydrochloric acid. Organicinorganic composite membranes for operation in polymer electrolyte membrane fuel cells (PEMFCs) were characterized and cell-tested. The physico-chemical properties of all membranes were investigated their thermal properties, water uptake, DSC and thermogravimetric analyzer (TGA). Branched copolymer and nano composite membranes exhibit proton conductivities from 1.7x10-3 to 8.3x10-3 S/cm2, water uptake from 22 to 26%, IEC from 1.28 to 1.46 meq/g and methanol diffusion coefficients from 1.2x10-7 to 1.7x10-7 cm2/S.