110-86-1

ULTRASOUND - PROMOTED COUPLING OF HETEROARYL HALIDES IN THE PRESENCE OF LITHIUM WIRE. NOVEL FORMATION OF ISOMERIC BIPYRIDINES IN A WURTZ - TYPE REACTION

Osborne, Alan G.,Glass, Kathryn J.,Staley, Miriam L.

, p. 3567 - 3568 (1989)

Ultrasonic irradiation of 2-bromopyridine in THF solution in the presence of lithium wire gives 2,2'-bipyridine, 2,4'-bipyridine and 4,4'-bipyridine, a novel formation of isomers in a Wurtz-type reaction.Similar reaction with 3-bromopyridine mainly results in debromination.

Photochemistry of N-(pyrimidin-2-one-4-yl)pyridinium derivatives. The ring contraction of pyrimidinone into imidazolinone

Wenska,Skalski,Paszyc,Gdaniec

, p. 2178 - 2184 (1995)

Photochemical reactions (λ > 300 nm) of N-(1-methylpyrimidin-2-one)- and N-(1,5-dimethyl-pyrimidin-2-one)pyridinium chlorides were studied in deoxygenated aqueous solution at various pH's. Only the former compound was found to be reactive under these conditions to give pyrimidine ring contraction photoproducts 1-methyl-4-imidazolin-2-one and 1-methyl-4-imidazolin-2-one-5-carboxyaldehyde, with pH-dependent chemical yields. The photochemical pyrimidine ring contraction reaction does not occur for other photochemically reactive pyrimidin-2-ones bearing 3-methylimidazolium-1,1,2,4-triazol-1-yl, or imidazol-1-yl as substituents at the C-4 position. The suggested mechanism of the reaction involves the addition of water to the pyrimidinone part of the N-(1-methylpyrimidin-2-one)pyridinium salt in the excited triplet state as the primary photochemical step. Addition of alcohol to the pyridinium ring was found to be the major reaction under irradiation of N-(1-methylpyrimidin-2-one-4-yl)pyridinium chloride in methanol.

Kinetics, mechanism, and thermochemistry of the gas-phase reaction of atomic chlorine with pyridine

Zhao,Huskey,Olsen,Nicovich,McKee,Wine

, p. 4383 - 4394 (2007)

A laser flash photolysis-resonance fluorescence technique has been employed to study the kinetics of the reaction of atomic chlorine with pyridine (C 5H5N) as a function of temperature (215-435 K) and pressure (25-250 Torr) in nitrogen bath gas. At T ≥ 299 K, measured rate coefficients are pressure independent and a significant H/D kinetic isotope effect is observed, suggesting that hydrogen abstraction is the dominant reaction pathway. The following Arrhenius expression adequately describes all kinetic data at 299-435 K for C5H5N: k1a = (2.08 ± 0.47) × 10-11 exp[-(1410 ± 80)/T] cm 3 molecule-1 s-1 (uncertainties are 2σ, precision only). At 216 K ≤ T ≤ 270 K, measured rate coefficients are pressure dependent and are much faster than computed from the above Arrhenius expression for the H-abstraction pathway, suggesting that the dominant reaction pathway at low temperature is formation of a stable adduct. Over the ranges of temperature, pressure, and pyridine concentration investigated, the adduct undergoes dissociation on the time scale of our experiments (10 -5-10-2 s) and establishes an equilibrium with Cl and pyridine. Equilibrium constants for adduct formation and dissociation are determined from the forward and reverse rate coefficients. Second- and third-law analyses of the equilibrium data lead to the following thermochemical parameters for the addition reaction: ΔrH°298 = -47.2 ± 2.8 kJ mol-1, ΔrH°0 = -46.7 ± 3.2 kJ mol-1, and ΔrS° 298 = -98.7 ± 6.5 J mol-1 K-1. The enthalpy changes derived from our data are in good agreement with ab initio calculations reported in the literature (which suggest that the adduct structure is planar and involves formation of an N-Cl σ-bond). In conjunction with the well-known heats of formation of atomic chlorine and pyridine, the above ΔrH values lead to the following heats of formation for C 5H5N-Cl at 298 K and 0 K: ΔfH° 298 = 216.0 ± 4.1 kJ mol-1, Δ fH°0 = 233.4 ± 4.6 kJ mol-1. Addition of Cl to pyridine could be an important atmospheric loss process for pyridine if the C5H5N-Cl product is chemically degraded by processes that do not regenerate pyridine with high yield. the Owner Societies.

Pyridyl-and pyridylperoxy radicals-a matrix isolation study

Korte, Andre,Mardyukov, Artur,Sander, Wolfram

, p. 1324 - 1329 (2014)

The three isomeric pyridyl radicals 2a-c were synthesised using flash vacuum pyrolysis in combination with matrix isolation and characterised by infrared spectroscopy. The IR spectra are in good agreement with spectra calculated using density functional theory methods. The reaction of the pyridyl radicals 2 with molecular oxygen leads to the formation of the corresponding pyridylperoxy radicals 3a-c. The peroxy radicals 3 are photolabile, and irradiation results in syn-anti isomerisation of 3a and 3b and ring expansion of all three isomers of 3.

Selective and Efficient Photoinactivation of Intracellular Staphylococcus aureus and MRSA with Little Accumulation of Drug Resistance: Application of a Ru(II) Complex with Photolabile Ligands

Sun, Weize,Jian, Yao,Zhou, Mengxue,Yao, Yishan,Tian, Na,Li, Chao,Chen, Jun,Wang, Xuesong,Zhou, Qianxiong

, p. 7359 - 7370 (2021)

Novel antibacterial agents capable of efficiently sterilizing intracellular Staphylococcus aureus and methicillin-resistant S. aureus (MRSA) but with low cytotoxicity and low resistance development are quite appealing. In this work, three Ru(II) complexes with photolabile ligands were explored to realize such a goal. Complex 3 (5 μM) can inhibit more than 90% growth of S. aureus/MRSA that has invaded in J774A.1 cells upon visible light irradiation, being much more efficient than vancomycin. In similar conditions, negligible dark- and phototoxicity were found toward the host cells. The bactericidal activity is highly correlated with DNA covalent binding by the Ru(II) fractions generated after ligand photodissociation. Moreover, S. aureus quickly developed resistance toward vancomycin, while negligible resistance toward complex 3 even after 700 generations was obtained. These appealing results may pave a new way for fighting against intracellular antibiotic-resistant pathogens.

Bis(μ-acetato)(μ-oxo)bis(tris(pyridine)ruthenium(III)) Ion: A Ruthenium Analogue of the Hemerythrin Active Center

Sasaki, Yoichi,Suzuki, Masakazu,Tokiwa, Ayako,Ebihara, Masahiro,Yamaguchi, Tadashi,et al.

, p. 6251 - 6252 (1988)

Ruthenium(III) is known to form the Ru2(μ-OH)2(μ-CH3COO) core rather an Ru2(μ-O)(μ-CH3COO)2 species with the facial-blocking ligand tacn.We wish to report here a new dimeric complex, III2(μ-O)(μ-CH3COO)2(py)6>2+ (py=pyridine).

Crystalline CrV0.95P0.05O4 catalyst for vapor-phase oxidation of picolines

Song, Zhaoxia,Matsushita, Toshiyuki,Shishido, Tetsuya,Takehira, Katsuomi

, p. 1306 - 1307 (2002)

CrV0.95P0.05O4 prepared as a pure crystalline form was found to be highly active for the vapor-phase oxidation of picolines to the corresponding aldehydes and acids in the presence of water.

Photoinduced electron transfer reactions: Nitrogen-oxygen bond cleavage in reduced N-(aryloxy)pyridinium and N,N′-dialkoxy-4,4′-bipyridinium salts

W?lfle, Ingrid,Lodaya, Jayant,Sauerwein, Bj?rn,Schuster, Gary B.

, p. 9304 - 9309 (1992)

N-(Aryloxy)pyridinium cations and N,N-dialkoxy-4,4′-bipyridinium dications form charge-transfer complexes with neutral hydrocarbons. Irradiation of these charge-transfer complexes leads to the cleavage of the nitrogen-oxygen bond and the formation of an aryloxy radical in the first case, but no reaction is observed for the second. In contrast, electron transfer to the dialkoxybipyridinium cation from the triplet state of 9-acetylanthracene leads to nitrogen-oxygen bond cleavage and the formation of an alkoxy radical. The rate constants for nitrogen-oxygen bond cleavage (kBC) in the reduced pyridinium salts were estimated by time-resolved laser spectroscopy. For N-(4-cyanophenoxy)pyridinium tetrafluoroborate, kBC> 1011 s-1, and for N,N-diethoxy-4,4′-bipyridinium (bis)hexafluorophosphate), kBC = 1.4 × 104 s-1. The effects of structure on the dynamics of the excited charge-transfer complexes and on kBC are discussed.

In situ DRIFTS study of picoline oxidation over CrV0.95P0.05O4 catalyst

Shishido,Song,Matsushita,Takaki,Takehira

, p. 2710 - 2718 (2003)

The catalytic behaviour of CrV0.95P0.05O4 has been investigated in the selective oxidations of 2-, 3- and 4-picolines by in situ DRIFTS, and the model of picoline adsorption and the oxidation mechanism are proposed. Both Lewis and Bronsted acid sites were detected on the surface of CrV0.95P0.05O4, and the number of the latter increased on the addition of steam in the reaction mixture, resulting in enhanced activity for selective oxidations. The enhanced activity due to water addition is interpreted by the fact that Bronsted acid sites are produced by the hydrolysis of V-O-Cr and activate picoline molecules by withdrawing the electrons of the pyridine ring, and at the same time, enable to accelerate the desorption of the acid products from the catalyst surface. Every 2-, 3- and 4-picoline was adsorbed on the catalyst surface via the N atom donating the electrons to the Bronsted acid sites, and the substituted methyl group was oxidized via hydrogen abstraction by surface oxide ion to form the radical intermediate, followed by oxygen insertion to produce the corresponding aldehyde and then acid. Even in the absence of gaseous oxygen, the oxygenated products were formed and observed over the catalyst surface by in situ DRIFTS. Thus, a Mars and van Krevelen mechanism was suggested for 2-, 3- and 4-picolines oxidations based on the spectral analysis. Both 2- and 4-picolines were more quickly oxidized than 3-picoline due to the inductive hyper-conjugative effect of nitrogen, resulting in an easy leaving of proton from the methyl group. 4-Picoline produced almost quantitatively isonocotinic acid, while 2-picoline afforded 2-picoline aldehyde as the main product due to the unstability of the acid product, i.e., the decarboxylation of picolinic acid took place to form pyridine.

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Schreiber,Shriner

, p. 1896 (1935)

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Organotin mediated nitration in heteroaromatic series using tetranitromethane or dinitrogen tetroxide

Favresse, Fabien,Fargeas, Valérie,Charrue, Pierre,Lebret, Bruno,Piteau, Marc,Quintard, Jean-Paul

, p. 187 - 190 (2000)

2-Trimethylstannylated benzo[b]furan, benzo[b]thiophene, N-substituted indoles and pyridine afford the corresponding nitro derivatives in regioselective fashion upon treatment with tetranitromethane (using sun-lamp irradiation in the case of N-containing

Mechanistic Studies in the Deoxygenation of Pyridine N-Oxide: A New 1,2 Elimination

Hwu, Jih Ru,Wetzel, John M.

, p. 400 - 402 (1985)

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Mathews, J. H.,Krause, E. L.,Bohnson, L. van

, p. 398 - 413 (1917)

Reductive Dimerization of Pyridine N-Oxide

Kurbatova, A. S.,Kurbatov, Yu. V.

, p. 113 (1988)

-

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Kline,Turkevich

, p. 1710,1714 (1944)

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Stepwise Mechanism of the Rhenium(V) Porphyrin Reaction with Pyridine, and the Chemical Structure of the Donor–Acceptor Complex

Bichan,Ovchenkova,Lomova

, p. 703 - 709 (2019)

Abstract: Chemical thermodynamics and UV, visible, IR, 1H NMR, and mass spectrometry are used to study the complex reaction of (5,15-bis(4'-methoxyphenyl)-3,7,13,17-tetramethyl-2,8,12,18-tetraethylporphinato) (oxo)(chloro)rhenium(V) (O=Re(Cl)P) with pyridine (Py) and the chemical structure of the product. The nature and stoichiometry of the reaction are established and the quantitative parameters of two-way stepwise reactions are determined during a complex reaction. There is reversible replacement of Cl– ions by pyridine molecules with constant K1 of (4.7 ± 1.1) × 102 L/mol and the formation of cationic complex compound [O=Re(Py)P]+Cl– in the first stage. The second stage is the reversible addition of two pyridine molecules ([O=Re(Py)3P]+Cl–) with constant K2 = (0.10 ± 0.03) L2/mol2. The reaction studied is a model for processes in self-assembling systems based on metalloporphyrins and pyridyl derivatives of carbon nanoforms for the formation of active layers with photoinduced charge separation in hybrid solar cells.

Energetics and structure of nicotinic acid (Niacin)

Gon?alves, Elsa M.,Bernardes, Carlos E. S.,Diogo, Hermínio P.,Minas Da Piedade, Manuel E.

, p. 5475 - 5485 (2010)

The standard molar enthalpies of formation and sublimation of crystalline (monoclinic, space group P21/c) nicotinic acid (NA), at 298.15 K, were determined as δfHm°(NA, cr) = -344.7 ± 1.2 kJ·mol-1 and δsubHm°(NA) = 112.1 ± 0.5 kJ·mol-1 by using combustion calorimetry, drop-sublimation Calvet microcalorimetry, and the Knudsen effusion method. The experimental determinations were all based on a sample of NIST Standard Reference Material 2151, which was characterized in terms of chemical purity, phase purity, and morphology. From the above results, δfHm° (NA, g) = -232.6 ± 1.3 kJ·mol-1 could be derived. On the basis of this value and on published experimental data, the enthalpy of the isodesmic reaction nicotinic acid(g) + benzene(g) ? benzoic acid(g) + pyridine(g) was calculated as -3.6 ± 2.7 kJ·mol-1 and compared with the corresponding predictions by the B3LYP/cc-pVTZ (-3.6 kJ·mol-1), B3LYP/aug-cc-pVTZ (-3.7 kJ·mol -1), B3LYP/6-311++G(d,p) (-4.2 kJ·mol-1), G3MP2 (-4.3 kJ·mol-1), and CBS-QB3 (-4.0 kJ·mol-1) quantum chemistry models. The excellent agreement between the experimental and theoretical results supports the reliability of the δfHm° (NA, cr), δsubHm°(NA), and δfHm°(NA, g) recommended in this work. These data can therefore be used as benchmarks for discussing the energetics of nicotinic acid in the gaseous and crystalline states and, in particular, to evaluate differences imparted to solid forms by the production and processing methods. Such differences are perhaps at the root of the significant inconsistencies found between the published enthalpies of sublimation of this important active pharmaceutical ingredient and thermochemical standard. The molecular packing in the crystalline phase studied in this work was also discussed and its influence on the molecular structure of nicotinic acid was analyzed by comparing bond distances and angles published for the solid state with those predicted by the B3LYP/cc-pVTZ method. No advantage in terms of accuracy of the structural predictions was found by the use of the larger aug-cc-pVTZ or 6-311++G(d,p) basis sets.

Structural and kinetic isotope effect studies of nicotinamidase (Pnc1) from saccharomyces cerevisiae

Smith, Brian C.,Anderson, Mark A.,Hoadley, Kelly A.,Keck, James L.,Cleland, W. Wallace,Denu, John M.

, p. 243 - 256 (2012)

Nicotinamidases catalyze the hydrolysis of nicotinamide to nicotinic acid and ammonia. Nicotinamidases are absent in mammals but function in NAD + salvage in many bacteria, yeast, plants, protozoa, and metazoans. We have performed structural and kinetic investigations of the nicotinamidase from Saccharomyces cerevisiae (Pnc1). Steadystate product inhibitor analysis revealed an irreversible reaction in which ammonia is the first product released, followed by nicotinic acid. A series of nicotinamide analogues acting as inhibitors or substrates were examined, revealing that the nicotinamide carbonyl oxygen and ring nitrogen are critical for binding and reactivity. X-ray structural analysis revealed a covalent adduct between nicotinaldehyde and Cys167 of Pnc1 and coordination of the nicotinamide ring nitrogen to the active-site zinc ion. Using this structure as a guide, the function of several residues was probed via mutagenesis and primary 15N and 13C kinetic isotope effects (KIEs) on V/K for amide bond hydrolysis. The KIE values of almost all variants were increased, indicating that C-N bond cleavage is at least partially rate limiting; however, a decreased KIE for D51N was indicative of a stronger commitment to catalysis. In addition, KIE values using slower alternate substrates indicated that C-N bond cleavage is at least partially rate limiting with nicotinamide to highly rate limiting with thionicotinamide. A detailed mechanism involving nucleophilic attack of Cys167, followed by elimination of ammonia and then hydrolysis to liberate nicotinic acid, is discussed. These results will aid in the design of mechanism-based inhibitors to target pathogens that rely on nicotinamidase activity.

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Ahrens

, p. 3039 (1893)

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5,6-DIHYDROPYRIDINE : SYNTHESIS AND CHARACTERIZATION

Lasne, Marie-Claire,Ripoll, Jean-Louis,Guillemin, Jean-Claude,Denis, Jean-Marc

, p. 3847 - 3848 (1984)

5,6-dihydropyridine 1 is synthesized either by flash vacuum thermolysis of 1-azabicyclo oct-2-ene 3 or by dehydrochlorination over solid bases of N-chloro-1,2,5,6-tetrahydropyridine 4 and characterized at low temperature by its (1)H and (13)C nmr and ir spectra.

A kinetic oxymoron: Concentration-dependent first-order rate constants for hydrolysis of ceftazidime

Fubara, Josephine O.,Notari, Robert E.

, p. 53 - 58 (1998)

The influence of pH, temperature, and buffers on the hydrolysis of 10- 4 M ceftazidine was previously reported. The pH-rate profiles showed that maximum stability occurred in the pH-independent region from 4.5 to 6.5. In the present study, hydrolysis rates of 0.031, 0.14, 0.25, and 0.35 M ceftazidime were measured at 30 and 65°C, pH 5.5-6.2. The data were consistent with β-lactam hydrolysis and the rapid release of pyridine. The sum of the time-dependent concentrations of ceftazidime and pyridine provided mass balance. Simultaneous nonlinear regression for ceftazidime loss and pyridine formation provided similar rate constants (k) to those determined from first-order plots of ceftazidime loss. Although the loss of ceftazidime was first-order for each initial concentration, the k values increased as the initial concentrations increased. Plots of k versus initial concentration were linear with intercepts similar to the k values for 10-4 M solutions, thus implying that ceftazidime catalyzed its own degradation. At the pH of these studies ceftazidime exists as a base. The ceftazidime catalytic constant, calculated from the slope of the plot, was similar to that found for the general-base catalyst, HPO42-. Therefore, it is feasible that ceftazidime also behaved as a intermolecular general-base catalyst. However, first-order plots exhibited excellent linearity even though the catalyst (ceftazidime) was consumed. This would require that the catalytic moieties on ceftazidime remained relatively constant throughout its hydrolysis. This hypothesis was shown to be consistent with literature reports which indicate that the general-base catalytic groups can remain relatively constant during cephalosporin hydrolysis.

Hydrolysis kinetics of 2-cyanopyridine, 3-cyanopyridine, and 4-cyanopyridine in high-temperature water

Fu, Jie,Ren, Haoming,Shi, Chaojun,Lu, Xiuyang

, p. 641 - 648 (2012)

We report herein the kinetic studies on hydrolysis of three cyanopyridines in high-temperature water. 3-Cyanopyridine, 4-cyanopyridine and 2-cyanopyridine underwent consecutive hydrolysis to the corresponding pyridinecarboxamides and picolinic acids. Further decarboxylation to pyridine was observed for 2-cyanopyridine hydrolysis. Experiments at different initial reactant concentrations revealed that these compounds exhibited the first-order kinetics. Experiments at different temperatures showed that the first-order rate constants displayed an Arrhenius behavior with activation energies of 74.3, 40.3, and 83.7 kJ mol-1 for 3-cyanopyridine, 4-cyanopyridine, 2-cyanopyridine, respectively. The activation energies obtained for 3-pyridinecarboxamide, 4-pyridinecarboxamide and 2-pyridinecarboxamide hydrolysis are 80.1, 32.7, and 70.5 kJ mol-1, respectively. The effect of substituent position on activation energies for cyanopyridine and pyridinecarboxamide hydrolysis is ortho a meta > para.

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Haitinger,Lieben

, p. 339 (1883)

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Alkylpyridiniums. 1. Formation in model systems via thermal degradation of trigonelline.

Stadler, Richard H,Varga, Natalia,Hau, Joerg,Vera, Francia Arce,Welti, Dieter H

, p. 1192 - 1199 (2002)

Trigonelline is a well-known precursor of flavor/aroma compounds in coffee and undergoes significant degradation during roasting. This study investigates the major nonvolatile products that are procured after trigonelline has been subjected to mild pyrolysis conditions (220-250 degrees C) under atmospheric pressure. Various salt forms of trigonelline were also prepared and the thermally produced nonvolatiles analyzed by thin layer chromatography, liquid chromatography-electrospray ionization tandem mass spectrometry, and (1)H and (13)C nuclear magnetic resonance. Results revealed the decarboxylated derivative 1-methylpyridinium as a major product of certain salts, the formation of which is positively correlated to temperature from 220 to 245 degrees C. Moreover, trigonelline hydrochloride afforded far greater amounts of 1-methylpyridinium compared to the monohydrate over the temperature range studied. Investigations into other potential quaternary amine products of trigonelline also indicate nucleophilic substitution reactions that lead to dialkylpyridiniums, albeit at concentration levels approximately 100-fold lower than those recorded for 1-methylpyridinium.

Miller,V.R.,Ryschkewitsch,G.E.

, p. 1558 - 1562 (1970)

Deaminative chlorination of aminoheterocycles

Ghiazza, Clément,Faber, Teresa,Gómez-Palomino, Alejandro,Cornella, Josep

, p. 78 - 84 (2021/12/23)

Selective modification of heteroatom-containing aromatic structures is in high demand as it permits rapid evaluation of molecular complexity in advanced intermediates. Inspired by the selectivity of deaminases in nature, herein we present a simple methodology that enables the NH2 groups in aminoheterocycles to be conceived as masked modification handles. With the aid of a simple pyrylium reagent and a cheap chloride source, C(sp2)?NH2 can be converted into C(sp2)?Cl bonds. The method is characterized by its wide functional group tolerance and substrate scope, allowing the modification of >20 different classes of heteroaromatic motifs (five- and six-membered heterocycles), bearing numerous sensitive motifs. The facile conversion of NH2 into Cl in a late-stage fashion enables practitioners to apply Sandmeyer- and Vilsmeier-type transforms without the burden of explosive and unsafe diazonium salts, stoichiometric transition metals or highly oxidizing and unselective chlorinating agents. [Figure not available: see fulltext.]

Coordination Chemistry of Borane in Solution: Application to a STING Agonist

Lemaire, Sébastien,Zhdanko, Alexander,van der Worp, Boris A.

supporting information, (2022/04/09)

Equilibrium constants were determined for ligand exchange reactions of borane complexes with various oxygen, sulfur, nitrogen, and phosphorus nucleophiles in solution, and a binding affinity scale was built spanning a range of 12 orders of magnitude. While the Keq are minimally dependent on the solvent, the rate of ligand exchange varies significantly. The fastest and slowest rates were observed in THF and CDCl3, respectively. Moreover, the ligand exchange rate differs in a very broad range depending on stability of the starting complex. Binding of BH3 was found to be much more sensitive to steric factors than protonation. Comparing nitrogen bases having equal steric properties, a linear correlation of BH3 binding affinity vs. Br?nsted acidity was found. This correlation can be used to quickly estimate the BH3 binding affinity of a substrate if pKa is known. Kinetic studies suggest the ligand exchange to occur as a bimolecular SN2 reaction unless other nucleophilic species were present in the reaction mixture.

Pd/C-catalyzed one-pot Suzuki-Miyaura cross-coupling/hydrogenation of pyridine derivatives

Pitna, Dinda B.,Tanaka, Nao,Usuki, Toyonobu

, (2021/07/31)

Using bromopyridines and methoxyphenyl boronic acid as starting materials, consecutive Suzuki-Miyaura cross-coupling and hydrogenation reactions were undertaken using a heterogeneous Pd/C catalyst in one-pot manner under mild conditions (balloon-pressure at room temperature for hydrogenation) with excellent yield. To counter Pd leaching as well as catalyst poisoning, addition of an appropriate amount of H2O was crucial to achieving successful AcOH-promoted hydrogenation, which ensured a selective reduction of the pyridine rings to the corresponding piperidines.