Showing papers on "Pyridine published in 1989"
TL;DR: The initial hydroxylation step in biodegradation of many pyridines is unusual in the incorporation of oxygen derived from water, and most simple pyridine derivatives, particularly hydroxypyridine derivatives and p Pyridinecarboxylic acids, are degraded via pathways involvinghydroxylated intermediates.
Abstract: Pyridine and pyridine derivatives occur in the environment as a result of industrial and agricultural activities. The fate of pyridines in the environment is a function of both abiotic and biotic processes, including photochemical transformations, complexation, surface attenuation, transport, and biological degradation. Pyridine is readily degraded in soil, and numerous bacteria isolated from soils or sludges are capable of growing on pyridines as sole sources of carbon and/or nitrogen. Numerous substituted pyridines are also susceptible to biodegradation, although major changes in biodegrada‐bility of the pyridine ring result from slight modification of the nature orposition of ring substituents. Bacteria apparently degrade most simple pyridine derivatives, particularly hydroxypyridines and pyridinecarboxylic acids, via pathways involving hydroxylated intermediates. The initial hydroxylation step in biodegradation of many pyridines is unusual in the incorporation of oxygen derived from water. Data sugges...
126 citations
TL;DR: In this article, the authors used a series of di-and mononuclear orthopalladated complexes of the type trans-Pd2L2X2 and trans-pdLL'Cl as catalysts in DMF medium.
119 citations
116 citations
TL;DR: In this article, a study of the hydrogenation of 1-hexene, small amounts of propylene were found together with the major product, hexane, which was attributed to an increase in the number of Bronsted acid sites.
106 citations
TL;DR: In this paper, the extinction coefficient of the N-H stretching ir absorption for coal-derived asphaltenes was calculated using X-ray photoelectron spectroscopy.
102 citations
TL;DR: It is suggested that rather than specific groups in the molecule also being involved, activity at nicotinic receptors depends on interactions between a flat part of the drug containing double‐bonds, or systems of double bonds, and a planar area in the receptor, possibly tyrosine or phenylalanine residues.
Abstract: 1. Although (-)-cytisine is a rigid structure, it occurs in the crystal in two distinct but very similar conformations in which the pyridone ring is tilted relative to the charged nitrogen atom at much the same angle as the pyridine ring is in (-)-nicotine hydrogen iodide. The carbonyl group in the pyridone ring of (-)-cytisine, however, is on the side of the ring opposite to pyridine nitrogen in (-)-nicotine. 2. The pKa of (-)-lobeline HCl at 25 degrees C is 8.6 (approx), indicating that (-)-lobeline is at least 90% in the protonated form at physiological pH (7.6). It is probably the phenyl 2-keto-ethyl part of (-)-lobeline, rather than the phenyl 2-hydroxy-ethyl part, which interacts with the receptor. 3. The combination within one molecule of a charged ('onium') nitrogen atom lying out of the plane of, and some distance (4.5-6.5 A) from, an aromatic ring is common to many compounds with nicotine-like activity (e.g. nicotine, cytisine, choline phenyl ether bromide, dimethyl-phenyl-piperazinium (DMPP) iodide, coryneine iodide and m-hydroxyphenylpropyl trimethyl ammonium iodide). In some molecules the aromatic ring can be replaced by an unsaturated group, such as carbonyl (e.g. acetylcholine) or double-bonds (e.g. anatoxin). 4. Activity at nicotinic receptors appears to involve interactions between the positively charged nitrogen atom and a negatively charged group, probably close to cysteine residues 192 and 193 in the receptor. It is suggested that rather than specific groups in the molecule also being involved, activity at nicotinic receptors depends on interactions between a flat part of the drug containing double-bonds, or systems of double bonds, and a planar area in the receptor, possibly tyrosine or phenylalanine residues.
96 citations
TL;DR: Kirby and Younas as mentioned in this paper showed that the relationship between the strength of the nucleophile and the measure of bond cleavage is described by an interaction coefficient, pxy = dp, = a~l,/dpKn,, = 0013, and provided evidence for concerted phosphoryl transfer between pyridine and oxygen bases.
Abstract: The slope of plots of log k2 against the pKa of the leaving group for reactions of uncharged, monoanionic, and dianionic oxygen nucleophiles with three phosphorylated pyridine monoanions changes from PI, = -098 to -079 as the pK, of the oxygen nucleophile increases from 36 to 157 (aqueous solution; 25 "C; ionic strength, 15) This coupling between the strength of the nucleophile and the measure of bond cleavage is described by an interaction coefficient, pxy = dp,,/dpK,,, = dp,,,/dpK,, = 0013, and provides evidence for concerted phosphoryl transfer between pyridine and oxygen bases The solvolysis of phosphorylated pyridines and of acetyl phosphate in aqueous solution also shows the behavior expected for a bimolecular substitution reaction with no metaphosphate intermediate: (1 ) The values of log k2 for reactions of oxygen nucleophiles, including water, with phosphorylated y-picoline monoanion follow a single line of slope 051 in a plot against log k2 for the corresponding bimolecular reactions with methyl 2,4-dinitrophenyl phosphate monoanion (Kirby, A J; Younas, M J Chem SOC B 1970, 1165) (2) Water behaves as expected for a nucleophile of its pKa in a Br~nsted-type plot of log k2 for reaction with phosphorylated y-picoline against the pK, of oxygen nucleophiles (3) The value of PI, = -102 for the hydrolysis of phosphorylated pyridines is less negative than the value of Ow' = -125 for complete breaking of the P-N bond (4) The value of Pi, = -102 for the reaction of water with phosphorylated pyridines fits the correlation of PI, against the pKa of oxygen nucleophiles for concerted, bimolecular reactions, with a slope ofp, = a~l,/dpKn,, = 0013 (5) The reactions of acetyl phosphate monoanion and dianion with aqueous alcohols show selectivity that depends on the pKa of the alcohol, with a larger selectivity for the less reactive dianion [50% aqueous alcohol (v/v), 55 "C] Metaphosphate monoanion has been discussed as a possible reaction intermediate since 1955 when eq 1 was proposed in order to explain the rapid hydrolysis of phosphate monoester monoanScheme I
88 citations
TL;DR: In this article, a series of postsynthesis modified ZSM5 zeolites was prepared using orthophosphoric acid, trimethylphosphine, and trimethyl phosphite.
84 citations
TL;DR: Oxygen transfer reactions from 2,6-disubstituted pyridine N-oxides to olefins were efficiently catalyzed by ruthenium porphyrins under mild conditions as mentioned in this paper.
84 citations
TL;DR: In this paper, the authors determined the constantes de rotation for quelques especes isotopiques de chaque systeme, and the constante de couplage quadripolaire a partir de la structure hyperfine des transitions rotationnelles.
Abstract: Determination des constantes de rotation pour quelques especes isotopiques de chaque systeme. Determination des constantes de couplage quadripolaire a partir de la structure hyperfine des transitions rotationnelles. Estimation des constantes de force d'elongation et des forces de liaison avec une analyse simple de distorsion centrifuge
82 citations
TL;DR: The ligands L sont la triphenylphosphine and la pyridine (trpy=terpyridine-2,2':6',2″) as mentioned in this paper.
Abstract: Photosubstitution de Ru [trpy] L 3 2+ et Ru [trpy] L 2 Cl + par l'acetonitrile, les ions chlorures, la pyridine, la picoline-4 et le propiononitrile. Les ligands L sont la triphenylphosphine et la pyridine (trpy=terpyridine-2,2':6',2″)
TL;DR: Arguments that have been presented to support a large effect of electrostatic repulsion on the rate of phosphoryl transfer are presented.
Abstract: Bimolecular phosphoryl transfer to anionic oxygen nucleophiles from phosphorylated pyridine monoanions is observed in aqueous solution at 25 OC and ionic strength 1.5. The dependence on ionic strength of several reactions suggests that screening of charge repulsion with an increase in ionic strength from 0 to 1.5 causes only - 5-fold increases in rate for these reactions between monoanions. Comparisons with reactions of neutral substrates suggest that the electrostatic repulsion which remains at ionic strength 1.5 causes a decrease in rate of - 10-fold or less. The small values of p,,, = 0.3 and the large negative values of PI, = -( 1 .O-0.8) for reactions of phosphorylated pyridines with anionic oxygen nucleophiles, and the small value of p,,, = 0.10 for the reverse reaction of substituted pyridines with acetyl phosphate dianion, suggest that there is little bond formation to the oxygen nucleophile and much bond cleavage to the pyridine leaving group in the dissociative, metaphosphate-like transition state of a concerted displacement reaction. The absence of an effect of Mg2+ binding on the value of p = 1.05-1.1 for the formation of phosphorylated pyridines shows that there is no significant charge/dipole interaction between Mg% and the substituent on the pyridine and that the effect of Mgz+ binding is less than the effect of protonation. The values of p,,, for phosphoryl transfer to nitrogen nucleophiles are not significantly different with oxygen and nitrogen leaving groups of the same pK,. Phosphoryl transfer to anionic oxygen nucleophiles is an im- portant biochemical reaction that usually involves a magnesium ion. Examples include the phosphorylation of AMPZ-, ADP3-, acetate ion, and 3-phosphoglycerate ionz Despite the biochemical importance of phosphoryl transfer to anionic nucleophiles, the transition state for the nonenzymatic reaction has not been characterized. One reason that these reactions have seldom been examined may be a widely held belief that electrostatic repulsion is large in phosphoryl transfer to anionic oxygen nucleophiles; in fact, the possibility has been raised that enzymes can catalyze phosphoryl transfer by overcoming electrostatic repulsion.z4 However, the arguments that have been presented to support a large effect of electrostatic repulsion on the rate of phosphoryl transfer are
TL;DR: In this article, a planar tridentate ligand based on 2,6-bis(N-pyrazolyl)pyridine was synthesized, which is a new family of planar ligands.
Abstract: We report here the synthesis of a new family of planar tridentate ligands based on 2,6-bis(N-pyrazolyl)pyridine
TL;DR: The reaction of various types of organic halides with electron deficient olefins under the influence of NiCl2 × 6 H2O in the presence of zinc and pyridine leads to formal addition products of hydrocarbons to CC-double bonds in good yield as discussed by the authors.
TL;DR: In this article, the solution chemistry of Cu(II) with a series of five planar tridentate nitrogen ligands, 2,6-bis(benzimidazol-2-yl)pyridine (bzimpy, 1), 2, 6-bis (l-methyl benzimidisol- 2-yl), pyridine, bzthpy and bzoxpy, are reported.
Abstract: The solution chemistry of Cu(II) with a series of five planar tridentate nitrogen ligands, 2,6-bis(benzimidazol-2-yl)pyridine (bzimpy, 1), 2,6-bis(l-methylbenzimidazol-2-yl)pyridine (mbzimpy, 2) 2,6-bis(benzothiazol-2-yl) pyridine (bzthpy, 3), 2,6-bis(benzoxazol-2-yl)pyridine (bzoxpy, 4), and 2,2′, 6′, 2″-terpyridyl (terpy, 5) is reported. Electronic and EPR spectra are consistent with the complexes [CuL]2+ having essentially tetragonal structure in solution, with the fourth coordination site in the plane of the ligand occupied by solvent. bzthpy and bzoxpy show smaller ligand-field splittings than bzimpy, mbzimpy, and terpy, and are easily decomplexed from the copper. Substitution of the coordinated solvent molecule in the plane of the ligand is observed with Cl− and OH− (provided that the ligand has no acidic protons) for all ligands except terpy. The reaction between [Cu(mbzimpy)]2+ and imidazole has been studied by potentiometric titration in MeCN/H2O 1:1 and shows strong binding of the imidazole in the plane (log K = 4.5 at 25°), and also the formation of an imidazolate-bridged dinuclear species.
TL;DR: In this paper, a short-time reaction of an amidoxime, RC(NH2)NOH, with an acyl chloride, R'COCl, in pyridine solution is described.
Patent•
30 May 1989
TL;DR: In this paper, an asymmetrically di-functionalized water soluble macrocyclic complexes of the lanthanide, actinide and yttrium ions were obtained by metal templated, Schiff-base, cyclic condensation of: (1) a functionalized 1,2-diaminoethane and a dicarbonyl compound selected from the group consisting of 2,6-dicaronylpyridine, 2, 6-diformylpyridine; (2,6)-dimitriitriitriyi pyridine
Abstract: Symmetrically di-functionalized water soluble macrocyclic complexes of lanthanide, actinide and yttrium ions were obtained by metal templated, Schiff-base, cyclic condensation of: (1) a functionalized 1,2-diaminoethane and a dicarbonyl compound selected from the group consisting of 2,6-dicarbonylpyridine, 2,6-diformylpyridine, 2,5-dicarbonylfuran, 2,5-diformylfuran, 2,5-dicarbonyl-thiophene and 2,5-diformylthiophene; or (2) 1,2-diaminoethane and a ring-substituted heterocyclic dicarbonyl compound selected from a group consisting of substituted 2,6-dicarbonylpyridine, substituted 2,6-diformylpyridine, substituted 2,5-dicarbonylfuran, substituted 2,5-diformylfuran; substituted 2,5-dicarbonyl thiophene, and substituted 2,5-diformylthiophene. Asymmetrically functionalized water soluble macrocyclic complexes of the lanthanide, actinide and yttrium ions were obtained by metal templated, Schiff-base, cyclic condensation of appropriately substituted diamine and dicarbonyl precursors, with such precursors contributing two heteroaromatic moieties (pyridine, furan, thiophene, or a combination thereof) to the resulting macrocyclic structure. The coordination complexes thus formed are kinetically stable in dilute aqueous solution. They are further reacted, or coupled, through a substituent on the 1,2-diaminoethane or on the pyridine, furan, or thiophene moieties, to one of the following: proteinaceous materials, polysaccharides, polynucleotides, other biologically compatible macromolecules or bridging molecules which, can be further reacted or coupled to the above mentioned substrates. These macrocyclic complexes are suitable in the preparation of reporter molecules and for magnetic resonance, radiation imaging and radiation therapy.
TL;DR: La reaction de calix[4] arenes avec le chlorhydrate de chloromethyl-2 pyridine donne des tetrakis-[pyridyl]-2 methoxy] calix.
Abstract: La reaction de calix[4] arenes avec le chlorhydrate de chloromethyl-2 pyridine donne des tetrakis-[pyridyl-2 methoxy] calix[4] arenes
TL;DR: In this paper, electron transfer from the substrate to the peroxide, which affords a perfluoroalkyl radical and a cation radical of the substrate in a solvent cage, is proposed.
Abstract: Perfluoroalkylations of nitrogen-containing heteroaromatic compounds with bis(perfluoroalkanoyl) peroxides were studied. Bis(trifluoroacetyl) peroxide, bis(heptafluorobutyryl) peroxide, and bis(pentadecafluoro-octanoyl) peroxide were found to be useful and effective reagents for perfluoromethylations, perfluoropropylations, or perfluoroheptylations of pyrrole and its derivatives, while these peroxides could not be applied for the perfluoroalkylations of pyridine or imidazole. For the perfluoroalkylations with the peroxides, electron transfer from the substrate to the peroxide, which affords a perfluoroalkyl radical and a cation radical of the substrate in a solvent cage, is proposed. In pyrroles, since the delocalization of the N lone pair to π-systems lowers the nucleophilicity of the N lone pair and increases the electron density at the π-orbital, the electron transfer readily occurred and perfluoroalkylated pyrroles were obtained in good yield and regioselectively. However, nucleophilic attack of the N lone pair to the O–O bond of the peroxide was superior to the electron transfer in pyridine or imidazole of which the N lone pairs are very nucleophilic.
TL;DR: Pyridine adsorption on ceria surfaces, prepared by thermal decomposition of diammonium hexanitratocerate at 400 °C, was studied by infrared spectroscopy and gravimetric techniques as mentioned in this paper.
TL;DR: In this paper, the adsorption of pyridine at an Ag (110) single crystal electrode has been studied, and the results showed that at potentials close to the potential of zero charge, pyridines assume a tilted orientation with the nitrogen atom facing the metal.
TL;DR: The rate of alkene epoxidation promoted by 30% H2O2 and catalysed by MnIII tetra (2,6-dichlorophenyl)porphyrin is strongly enhanced by the addition of lipophilic carboxylic acids and Lipophilic imidazole or pyridine axial ligands, in 1-8 : 1 and 1 : 1 molar ratios with respect to the porphyrin this article.
Abstract: The rate of alkene epoxidation promoted by 30% H2O2 and catalysed by MnIII tetra (2,6-dichlorophenyl)porphyrin is strongly enhanced by the addition of lipophilic carboxylic acids and lipophilic imidazole or pyridine axial ligands, in 1–8 : 1 and 1 : 1 molar ratios with respect to the porphyrin.
TL;DR: In this paper, a soluble (phthalocyaninato)copper (II) complex containing eight symmetrical benzo-15-crown-5 substituents was synthesized from quinoline or pyridine.
Abstract: A soluble (phthalocyaninato)copper(II) complex containing eight symmetrical benzo-15-crown-5 substituents, namely {2,3,9,10,16,17,23,24-octakis[[benzo-15-crown-5)-4′ -yl]oxymethyl]phthalocyaninato}copper(II) (2) from 1,2-bis{[benzo-15-crown-5)-4′-yl]oxymethyl}-4,5-dibromobenzene (1) and CuCN in quinoline or pyridine was synthesized. The crown-ether groups in 2 were shown to prefer intramolecular complexation with alkali metal ions.
TL;DR: A series of C-4 substituted pyrazolo[3,4-b]pyridine nucleosides have been synthesized and evaluated for their biological activity and the effects of these compounds on de novo purine and pyrimidine nucleotide biosynthesis was also evaluated.
Abstract: A series of C-4 substituted pyrazolo[3,4-b]pyridine nucleosides have been synthesized and evaluated for their biological activity. Successful synthesis of various C-4 substituted pyrazolo[3,4-b]pyridine nucleosides involves nucleophilic displacement by a suitable nucleophile at the C-4 position of 4-chloro-1H-pyrazolo[3,4-b]pyridine (5), followed by glycosylation of the sodium salt of the C-4 substituted pyrazolo[3,4-b]pyridines with a protected alpha-halopentofuranose. Use of this methodology furnished a simple and direct route to the beta-D-ribofuranosyl, beta-D-arabinofuranosyl, and 2-deoxy-beta-D-erythro-pentofuranosyl nucleosides of C-4 substituted pyrazolo[3,4-b]pyridines, wherein the C-4 substituent was azido, amino, methoxy, chloro, or oxo. The regiospecificity of these glycosylations was determined on the basis of UV data and the anomeric configuration was established by 1H NMR analysis. Conclusive structural assignment was made by a single-crystal X-ray diffraction study of three compounds, 15, 31, and 42, as representatives of ribo-2'-deoxy-, and aranucleosides, respectively. The stereospecific attachment of all three alpha-halogenoses appears to occur by a Walden inversion (SN2 mechanism) at the C-1 carbon of the halogenose by the anionic N-1 of pyrazolo[3,4-b]pyridine. All deprotected nucleosides were tested against various viruses and tumor cells in culture. The effects of these compounds on de novo purine and pyrimidine nucleotide biosynthesis was also evaluated. Among the compounds tested, 4-chloro-1-beta-D-ribofuranosylpyrazolo[3,4-b]pyridine (16) and 1-beta-D-ribofuranosyl-4,7-dihydro-4-oxopyrazolo[3,4-b]pyridine (19) were found to be moderately cytotoxic to L1210 and WI-L2 in culture.
TL;DR: In this paper, a Japanese bituminous coal (81.2%C) was extracted with pyridine at 200-400 °C to give an extraction yield of 50 wt% at 400 °C.
TL;DR: In this article, a monoaza crown ether substituted (phthalocyaninato)copper (II) complex and its water-soluble quaternary ammonium salt were prepared from the corresponding dibromomonoaza Crown ether derivative 1 and CuCN in pyridine.
Abstract: A monoaza crown ether substituted (phthalocyaninato)copper(II) complex 2 and its water-soluble quaternary ammonium salt 3 were prepared from the corresponding dibromomonoaza crown ether derivative 1 and CuCN in pyridine.
TL;DR: In this paper, a polyamide-imide-containing dicarboxylic acids and aromatic diamines using triphenyl phosphite in N-methyl-2-pyrrolidone (NMP)/pyridine solution in the presence of metal salts were synthesized by direct polycondensation reaction.
Abstract: Aliphatic-aromatic poly(amide-imide)s with high molecular weight (ηinh up to 2,91 dl/g in DMAc/5% LiCl) were synthesized by direct polycondensation reaction of imide-containing dicarboxylic acids and aromatic diamines using triphenyl phosphite in N-methyl-2-pyrrolidone (NMP)/pyridine solution in the presence of metal salts. The factors affecting the reaction of N-(trimellitoyl)glycine and 4,4′-oxydianiline were investigated. The molecular weight of the polymer varied with the amount of metal salts, showing a maximum at a concentration of about 1 wt.-% CaCl2 or about 2 wt.-% LiCl in the reaction mixture. A monomer concentration of about 0,2 mol/l gave the most favorable result. Among the solvents tested, NMP was most effective. Similarly, polycondensations of several combinations of three imide-diacids with various aromatic diamines were carried out. Solubility, thermal properties, and tensile properties of the polymers are discussed.
TL;DR: In this paper, surface enhancement factors of several pyridine vibrations were measured and range from 10{sup 3} to 10{Sup 6} and the strongest enhancements were observed in totally symmetric vibrations.
Abstract: Surface-enhanced hyper-Raman scattering by pyridine was observed in aqueous silver citrate sols. Surface enhancement factors of several pyridine vibrations were measured and range from 10{sup 3} to 10{sup 6}. The strongest enhancements were observed in the totally symmetric vibrations {nu}{sub 12}, {nu}{sub 1}, {nu}{sub 6e}, and {nu}{sub 8a} and the b{sub 2} vibration {nu}{sub 6b}. The surface enhancements observed are larger than predicted by electrodynamic theories of surface enhancement for simple spherical or spheriodal particles, but relative enhancements are consistent with electromagnetic surface enhancement selection rules for hyper-Raman scattering. Elastic incoherent scattering in Ag sols was observed at twice the laser frequency. The intensity of the elastic component was 10{sup 4} to 10{sup 6} times more intense than hyper-Rayleigh scattering from bulk pyridine and increased upon addition of pyridine to the silver sols.