- ULTRASOUND - PROMOTED COUPLING OF HETEROARYL HALIDES IN THE PRESENCE OF LITHIUM WIRE. NOVEL FORMATION OF ISOMERIC BIPYRIDINES IN A WURTZ - TYPE REACTION
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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.
- Osborne, Alan G.,Glass, Kathryn J.,Staley, Miriam L.
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- Stereochemistry and properties of the M(II)-N(py) coordination bond in the low-spin dipyridinated iron(II) and cobalt(II) phthalocyanines
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A comparison between the coordination bond M(II)-N(py) and vibrational properties and stereochemistry of the dipyridinated iron(II) and cobalt(II) phthalocyaninato complexes, FePc(py)2 and CoPc(py)2 (Pc=C32H16N8, py=C5H5N), is carried out using the single crystal X-ray diffraction and the vibrational spectroscopy. Both dipyridinated complexes have been synthesized in crystalline form by heating of the β-FePc or β-CoPc in pyridine at 160°C. The crystals are formed during the slowly cooling process. The crystal of FePc(py)2 and CoPc(py)2 are isostructural. They crystallize in the space group P21/c of the monoclinic system with two molecules per unit cell. The structural results and coordination bond properties are strictly related in these complexes. The Fe2+ and Co2+ cations are coordinated by four N-isoindole atoms of the phthalocyaninato(2-) macrocycle and axially by two nitrogen atoms of pyridine molecules to form a tetragonal bypyramid. The vibrational M-Nisoindole parameters are much more affected than the corresponding structural parameters by the difference in the electronic structure of the Co and Fe. The axial M(II)-N(py) bond length depends strongly on the electron configuration of the central metal. The value of the M(II)-N(py) bond length of 2.039(2) A? in FePc(py)2 and 2.340(2) A? in CoPc(py)2 clearly evidences on the localization of the unpaired electron on the dz2 orbital of the Co in the cobalt complex. The electron paramagnetic resonance (EPR) spectroscopy and magnetic susceptibility measurements have also detected the unpaired electron in the molecule of CoPc(py)2. EPR and magnetic susceptibility measurements performed on a solid sample of FePc(py)2 shown on its diamagnetic character. The importance of the d(π)→π*(Pc) back donation is manifested in the difference between the values of the C-Nisoindole and C-Nazamethine bond lengths of the Pc macrocycle.
- Janczak, Jan,Kubiak, Ryszard
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- Photochemistry of N-(pyrimidin-2-one-4-yl)pyridinium derivatives. The ring contraction of pyrimidinone into imidazolinone
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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.
- Wenska,Skalski,Paszyc,Gdaniec
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- Electrochemical reduction of halopyridines catalyzed by Ni0(bipy)2
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The possibility of electrochemical reduction of halopyridines in the presence of Ni0(bipy)2 (bipy = 2,2′-bipyridine) was shown, and the features of homo- and cross-coupling with participation of PyX (Py = 2-or 3-pyridyl, X = Cl, Br) were studied.
- Budnikova,Kargin
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- Kinetics, mechanism, and thermochemistry of the gas-phase reaction of atomic chlorine with pyridine
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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.
- Zhao,Huskey,Olsen,Nicovich,McKee,Wine
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- Synthesis of branched ultrahigh-molecular-weight polyethylene using highly active neutral, single-component Ni(II) catalysts
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Neutral nickel methyl complexes incorporating 2,8-diarylnaphthyl groups have been synthesized and characterized. Salicylaldiminato nickel systems 1a,b are exceptionally active neutral nickel single component catalysts for the polymerization of ethylene capable of producing lightly branched ultrahigh-molecular-weight polyethylene (UHMWPE). In addition, complex 1a shows a "quasi-living" polymerization behavior. (Chemical Equation Presented).
- Chen, Zhou,Mesgar, Milad,White, Peter S.,Daugulis, Olafs,Brookhart, Maurice
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- Pyridyl-and pyridylperoxy radicals-a matrix isolation study
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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.
- Korte, Andre,Mardyukov, Artur,Sander, Wolfram
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- 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
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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.
- Sun, Weize,Jian, Yao,Zhou, Mengxue,Yao, Yishan,Tian, Na,Li, Chao,Chen, Jun,Wang, Xuesong,Zhou, Qianxiong
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- Increase in the coordination number of a cobalt porphyrin after photo-induced interfacial electron transfer into nanocrystalline TiO2
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Spectroscopic, electrochemical, and kinetic data provide compelling evidence for a coordination number increase initiated by interfacial electron transfer. Light excitation of CoI(meso-5,10,15,20-tetrakis(4- carboxyphenyl)porphyrin) anchored to a nanocrystalline TiO2 thin film, abbreviated CoIP/TiO2, immersed in an acetonitrile:pyridine electrolyte resulted in rapid excited state injection, kinj > 108 s-1, to yield Co IIP/TiO2(e-), followed by axial coordination of pyridine to the CoIIP and hence an increase in coordination number from four to five. The formal oxidation state and coordination environment of the Co metalloporphyrin on TiO2 were assigned through comparative studies in fluid solution as well as by comparisons to previously reported data. The kinetics for pyridine coordination were successfully modeled with a pseudo-first order kinetic model that yielded a second-order rate constant of k+py = 2 × 108 M-1 s-1. Spectro-electrochemical measurements showed that pyridine coordination resulted in a ～200 mV negative shift in the CoII/I reduction potential, E°(CoII/I/TiO2) = -0.72 V and E°(Co II/I(py)/TiO2) = -0.85 V vs NHE. With some assumptions, this indicated an equilibrium formation constant Kf = 400 M -1 for the CoIIP(py)/TiO2 compound. The kinetics for charge recombination were non-exponential under all conditions studied, but were successfully modeled by the Kohlrausch-Williams-Watts (KWW) function with observed rate constants that decreased by about a factor of 100 when pyridine was present. The possible mechanisms for charge recombination are discussed.
- Achey, Darren,Ardo, Shane,Meyer, Gerald J.
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- Bis(μ-acetato)(μ-oxo)bis(tris(pyridine)ruthenium(III)) Ion: A Ruthenium Analogue of the Hemerythrin Active Center
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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).
- Sasaki, Yoichi,Suzuki, Masakazu,Tokiwa, Ayako,Ebihara, Masahiro,Yamaguchi, Tadashi,et al.
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- REDUCTIVE DECYANATION OF PYRIDINECARBONITRILES BY TITANIUM TRICHLORIDE
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Titanium(III) chloride promotes reductive decyanation of 4-CN- and 2-CN-pyridine.The role of complex forming agents is discussed.
- Clerici, A.,Porta, O.
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- Crystalline CrV0.95P0.05O4 catalyst for vapor-phase oxidation of picolines
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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.
- Song, Zhaoxia,Matsushita, Toshiyuki,Shishido, Tetsuya,Takehira, Katsuomi
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- Photoinduced electron transfer reactions: Nitrogen-oxygen bond cleavage in reduced N-(aryloxy)pyridinium and N,N′-dialkoxy-4,4′-bipyridinium salts
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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.
- W?lfle, Ingrid,Lodaya, Jayant,Sauerwein, Bj?rn,Schuster, Gary B.
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- Synthesis and properties of a new (octaethylporphyrinato)-manganese(III)–pyridinyl-substituted pyrrolidinofullerene dyad
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The formation of a porphyrin–fullerene dyad from 2′-(pyridin-4-yl)-5′-(pyridin-2-yl)-1′-(pyridin-3-ylmethyl)-2′,5′-dihydro-1′H-pyrrolo[3′,4′: 1,9](C60-Ih)[5,6]fullerene and (2,3,7,8,12,13,17,18-octaethylporphyrinato) manganese(III) with axial chloride ligand has been studied on a quantitative level with the goal of obtaining supramolecules possessing biological activity. Preliminarily, the reaction of manganese(III) porphyrin with pyridine has been studied. The donor–acceptor dyads are formed either instantaneously and reversibly (pyridine) or slowly and irreversibly (substituted fullerene). In both cases, the reaction is a one-step process for which thermodynamic and kinetic parameters have been determined. The results can be used to optimize conditions for the synthesis of porphyrin–fullerene dyads. The obtained dyads have been characterized by spectral data and stability constants.
- Ovchenkova,Bichan,Lomova
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- In situ DRIFTS study of picoline oxidation over CrV0.95P0.05O4 catalyst
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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.
- Shishido,Song,Matsushita,Takaki,Takehira
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- Acid-Base Kinetics of Pyridine Studied with a Slow Spectrophotometric Indicator in Methanol
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The protonation-deprotonation kinetics of pyridine in methanol has been studied by the electric field jump technique.Kinetic measurements of the electric field insensitive equilibrium B + H+ (k1) BH+ (k-1), where B denotes pyridine, were obtained by coupling the equilibrium with a field-sensitive, visibly colored indicator equilibrium.Use of the "slow" indicator 2,2',4,4',6,6'-hexanitrodiphenylamine allowed observation of the slower of the two relaxation times of the coupled system in a time range where measurements could be made with sufficient precision for a reliable extraction of the rate constants k1 and k-1 from the data.The values obtained are k1 = 1.57 +/- 0.32 * 1010 dm3mol-1s-1 and k-1 = 8.43 +/- 1.69 * 104 s-1.The value for k1 is within the expected limits for a diffusion-controlled reaction in this solvent.An ionic reaction radius of 3.9 Angstroem is calculated from the protonation rate constant value, which indicates that the neutral species involved is probably a hydrogen-bonded pyridine-methanol complex rather than free pyridine.The value for k-1 is 1 order of magnitude greater than the constant for methyl-substituted pyridines, reflecting unsubstituted pyridine's lower basicity in methanol.
- Marshall, David B.,Eyring, Edward M.,Strohbusch, Frank,White, Robert D.
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- Activation and deactivation of a chemical transformation by an electromagnetic field: Evidence for specific microwave effects in the formation of grignard reagents
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It's field density, not temperature! Modifying the electric field strength in a microwave experiment can completely change the outcome of a reaction. Whereas a low field strength in Grignard reagent formation from Mg metal and aryl halide leads to acceleration of the initiation step, using a high field strength at the same temperature suppresses Mg insertion, favoring solvent decomposition and passivation of the Mg metal (see scheme). Copyright
- Gutmann, Bernhard,Schwan, Alexander M.,Reichart, Benedikt,Gspan, Christian,Hofer, Ferdinand,Kappe, C. Oliver
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- Organotin mediated nitration in heteroaromatic series using tetranitromethane or dinitrogen tetroxide
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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
- Favresse, Fabien,Fargeas, Valérie,Charrue, Pierre,Lebret, Bruno,Piteau, Marc,Quintard, Jean-Paul
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- Examining the Effects of Monomer and Catalyst Structure on the Mechanism of Ruthenium-Catalyzed Ring-Opening Metathesis Polymerization
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The mechanism of Ru-catalyzed ring-opening metathesis polymerization (ROMP) is studied in detail using a pair of third generation ruthenium catalysts with varying sterics of the N-heterocyclic carbene (NHC) ligand. Experimental evidence for polymer chelation to the Ru center is presented in support of a monomer-dependent mechanism for polymerization of norbornene monomers using these fast-initiating catalysts. A series of kinetic experiments, including rate measurements for ROMP, rate measurements for initiation, monomer-dependent kinetic isotope effects, and activation parameters were useful for distinguishing chelating and nonchelating monomers and determining the effect of chelation on the polymerization mechanism. The formation of a chelated metallacycle is enforced by both the steric bulk of the NHC and by the geometry of the monomer, leading to a ground-state stabilization that slows the rate of polymerization and also alters the reactivity of the propagating Ru center toward different monomers in copolymerizations. The results presented here add to the body of mechanistic work for olefin metathesis and may inform the continued design of catalysts for ROMP to access new polymer architectures and materials.
- Wolf, William J.,Lin, Tzu-Pin,Grubbs, Robert H.
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- 2,2'-Diphenyl-Δ3,3'-bi-3H-indole-1,1'-dioxide: Competitive Demethylation and Redox Reactions
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Competitve demethylation and redox reactions induced by 2,2'-diphenyl-Δ3,3'-bi-3H-indole-1,1'-dioxide, 1 (dinitrone) on several nitrogen bearing compounds (pyridines, amides, indoles, hydrazones and amines) are reported. - Keywords: 2,2'-Diphenyl-Δ3,3'-bi-3H-indole-1,1'-dioxide; Demethylation; Oxidation
- Bruni, Paolo,Conti, Carla,Tosi, Giorgio
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- Stepwise Mechanism of the Rhenium(V) Porphyrin Reaction with Pyridine, and the Chemical Structure of the Donor–Acceptor Complex
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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.
- Bichan,Ovchenkova,Lomova
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- Structures, Lewis Acidities, Electrophilicities, and Protecting Group Abilities of Phenylfluorenylium and Tritylium Ions
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The isolation, characterization, and the first X-ray structures of a fluorenylium ion and its Lewis adducts with nitrogen- and phosphorus-centered Lewis bases are reported. Kinetics of the reactions of a series of fluorenylium ions with reference π-, σ-, and n-nucleophiles of various sizes and nucleophilicities allowed the interplay between electronic and structural parameters on the electrophilicities of these planarized tertiary carbenium ions to be elucidated. Structure–reactivity correlations and extensive comparisons of their reactivities with those of di- and triarylcarbenium ions are described. Quantitative determination of the electrofugalities of fluorenylium ions revealed to which extent they are complementing tritylium ions as protecting groups and how their tuning is possible. Determination of the equilibrium constants of the Lewis adducts formation between pyridines of calibrated Lewis basicities and phenylfluorenylium and tritylium ions allowed the determination of their Lewis acidities and to showcase the potential of these carbon-centered Lewis acids in catalysis.
- Follet, Elsa,Mayer, Peter,Berionni, Guillaume
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- Energetics and structure of nicotinic acid (Niacin)
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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.
- Gon?alves, Elsa M.,Bernardes, Carlos E. S.,Diogo, Hermínio P.,Minas Da Piedade, Manuel E.
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- New silver(I) pyridinecarboxylate complexes: Synthesis, characterization, and antimicrobial therapeutic potential
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Silver(I) pyridinecarboxylates (AgPIC (1), AgNIC (2), [Ag(HDIPIC)]0. 75H2O (3), PIC = picolinate, NIC = nicotinate, HDIPIC = dipicolinate) were prepared by solvothermal syntheses and their characterization were completed by elemental, spectral, and thermal analyses. To assign the pyridinecarboxylate coordination mode in the complexes, detailed mid-infrared spectral data and Δ(as-s) comparisons were accomplished. In addition, silver(I) pyridinecarboxylate antimicrobial activities and stability by 1H NMR spectra were determined. Moreover, the spectral, thermal, and antimicrobial properties of silver(I) and previously prepared zinc(II) pyridinecarboxylates were compared and discussed. 2014
- Vargova,Almasi,Hudecova,Titkova,Rostasova,Zelenak,Gyoeryova
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- Structural and kinetic isotope effect studies of nicotinamidase (Pnc1) from saccharomyces cerevisiae
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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.
- Smith, Brian C.,Anderson, Mark A.,Hoadley, Kelly A.,Keck, James L.,Cleland, W. Wallace,Denu, John M.
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- Nickel-catalyzed reductive defunctionalization of esters and amides to aromatic hydrocarbons
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The removal of ester and amide groups is of fundamental significance in organic syntheses. Under non-catalytic conditions, hydride sources are chiefly used for their reduction. Recently developed Ni-catalyzed one-pot reductive activation of esters and ami
- Mondal, Manoj,Bharali, Pankaj
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- 5,6-DIHYDROPYRIDINE : SYNTHESIS AND CHARACTERIZATION
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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.
- Lasne, Marie-Claire,Ripoll, Jean-Louis,Guillemin, Jean-Claude,Denis, Jean-Marc
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- A kinetic oxymoron: Concentration-dependent first-order rate constants for hydrolysis of ceftazidime
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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.
- Fubara, Josephine O.,Notari, Robert E.
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- Hydrolysis kinetics of 2-cyanopyridine, 3-cyanopyridine, and 4-cyanopyridine in high-temperature water
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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.
- Fu, Jie,Ren, Haoming,Shi, Chaojun,Lu, Xiuyang
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- Protolytic Kinetics of Some Pyridine Derivatives in Non-buffered Aqueous Solution
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The deprotonation rates of the conjugate acids of 2,2'-bipyridine and pyridine, and the protonation rates of 2-aminopyridine and 4-aminopyridine were measured in non-buffered aqueous solution by means of a stopped-flow pH jump method.These pyridine derivatives showed quite slow protolytic behavior, similar to that of 1,10-phenanthroline and cyclopentadienes: the deprotonation rate constants of conjugate acids of 2,2'-bipyridine and pyridine are (4.8 +/- 0.7)*10-1 and (6.0 +/- 2.2)*10-2 s-1, respectively.The deprotonation rates of barbituric acid and acetylcyclopentadiene as authentic samples were also measured.Their deprotonation rate constants are in good agreement with the literature values, this demonstrates the validity and the applicability of the stopped-flow pH jump method.This method is superior to the NMR method for the determination of the protontransfer rates of azaaromatic compounds.
- Ando, Isao,Ujimoto, Kikujiro,Kurihara, Hirondo
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- Synthesis of Indolizines from Pyridinium Salts and Ethyl Bromodifluoroacetate
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Here we present a novel annulation of pyridinium salts with BrCF2CO2Et to access the indolizine derivatives with high efficiency. The α substitution of pyridine plays a key role in determining the reaction pathways. Various types of indolizines can be conveniently accessed from easily available pyridinium salts under mild and simple reaction conditions.
- Hou, Xiaoya,Zhou, Sen,Li, Yuli,Guo, Minjie,Zhao, Wentao,Tang, Xiangyang,Wang, Guangwei
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- Alkylpyridiniums. 1. Formation in model systems via thermal degradation of trigonelline.
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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.
- Stadler, Richard H,Varga, Natalia,Hau, Joerg,Vera, Francia Arce,Welti, Dieter H
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- Complexes of 2,2',2 -Nitrilotriphenol. Part 3. Crystal and Molecular Structures of Three Aluminium Complexes
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Crystal and molecular structures of three Al(III) complexes of the tripod ligand 2,2',2 -nitrilotriphenolate (I) are presented.They all show 5-coordinate Al in approximately trigonal bipyramidal geometry, with an external nucleophile X occupying the second axial position.X is OH- in -+ (quin = quinuclidine), N in (py = pyridine), and one of the O-atoms of a second molecule in the dimeric 2>.Correlated variations in the axial bond lengths of the trigonal bipyramid are observed: 2> Al-Nint. = 2.094 Angstroem, Al-Oext. = 1.850 Angstroem; : Al-Nint. = 2.153 Angstroem, Al-Next. = 1.992 Angstroem; -: Al-Nint. = 2.278 Angstroem, Al-Oext. = 1.765 Angstroem.They are interpreted in terms of a dissociative reaction path at the Al(III) centre.
- Mueller, Edgar,Buergi, Hans-Beat
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- Deaminative chlorination of aminoheterocycles
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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.]
- Ghiazza, Clément,Faber, Teresa,Gómez-Palomino, Alejandro,Cornella, Josep
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- CROSSLINKED ARTIFICIAL NUCLEIC ACID ALNA
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The present invention provides a novel bridged artificial nucleic acid and an oligomer containing the same as a monomer. The present invention provides specifically a compound represented by general formula (I) (wherein each symbol is the same as defined in the specification) or salts thereof; as well as an oligonucleotide compound represented by general formula (I′) (wherein each symbol is the same as defined in the specification) or salts thereof.
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- Coordination Chemistry of Borane in Solution: Application to a STING Agonist
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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.
- Lemaire, Sébastien,Zhdanko, Alexander,van der Worp, Boris A.
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supporting information
(2022/04/09)
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- Exploiting a silver-bismuth hybrid material as heterogeneous noble metal catalyst for decarboxylations and decarboxylative deuterations of carboxylic acids under batch and continuous flow conditions
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Herein, we report novel catalytic methodologies for protodecarboxylations and decarboxylative deuterations of carboxylic acids utilizing a silver-containing hybrid material as a heterogeneous noble metal catalyst. After an initial batch method development, a chemically intensified continuous flow process was established in a simple packed-bed system which enabled gram-scale protodecarboxlyations without detectable structural degradation of the catalyst. The scope and applicability of the batch and flow processes were demonstrated through decarboxylations of a diverse set of aromatic carboxylic acids. Catalytic decarboxylative deuterations were achieved on the basis of the reaction conditions developed for the protodecarboxylations using D2O as a readily available deuterium source.
- ?tv?s, Sándor B.,Fül?p, Ferenc,Kónya, Zoltán,Kukovecz, ákos,Márton, András,Mészáros, Rebeka,Pálinkó, István,Szabados, Márton,Varga, Gábor
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p. 4685 - 4696
(2021/07/12)
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- Pd/C-catalyzed one-pot Suzuki-Miyaura cross-coupling/hydrogenation of pyridine derivatives
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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.
- Pitna, Dinda B.,Tanaka, Nao,Usuki, Toyonobu
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- Clean protocol for deoxygenation of epoxides to alkenes: Via catalytic hydrogenation using gold
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The epoxidation of olefin as a strategy to protect carbon-carbon double bonds is a well-known procedure in organic synthesis, however the reverse reaction, deprotection/deoxygenation of epoxides is much less developed, despite its potential utility for the synthesis of substituted olefins. Here, we disclose a clean protocol for the selective deprotection of epoxides, by combining commercially available organophosphorus ligands and gold nanoparticles (Au NP). Besides being successfully applied in the deoxygenation of epoxides, the discovered catalytic system also enables the selective reduction N-oxides and sulfoxides using molecular hydrogen as reductant. The Au NP catalyst combined with triethylphosphite P(OEt)3 is remarkably more reactive than solely Au NPs. The method is not only a complementary Au-catalyzed reductive reaction under mild conditions, but also an effective procedure for selective reductions of a wide range of valuable molecules that would be either synthetically inconvenient or even difficult to access by alternative synthetic protocols or by using classical transition metal catalysts. This journal is
- Fiorio, Jhonatan L.,Rossi, Liane M.
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p. 312 - 318
(2021/01/29)
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- Photocatalytic deoxygenation of N-O bonds with rhenium complexes: From the reduction of nitrous oxide to pyridineN-oxides
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The accumulation of nitrogen oxides in the environment calls for new pathways to interconvert the various oxidation states of nitrogen, and especially their reduction. However, the large spectrum of reduction potentials covered by nitrogen oxides makes it difficult to find general systems capable of efficiently reducing variousN-oxides. Here, photocatalysis unlocks high energy species able both to circumvent the inherent low reactivity of the greenhouse gas and oxidant N2O (E0(N2O/N2) = +1.77 Vvs.SHE), and to reduce pyridineN-oxides (E1/2(pyridineN-oxide/pyridine) = ?1.04 Vvs.SHE). The rhenium complex [Re(4,4′-tBu-bpy)(CO)3Cl] proved to be efficient in performing both reactions under ambient conditions, enabling the deoxygenation of N2O as well as synthetically relevant and functionalized pyridineN-oxides.
- Anthore-Dalion, Lucile,Cantat, Thibault,Kjellberg, Marianne,Nicolas, Emmanuel,Ohleier, Alexia,Thuéry, Pierre
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p. 10266 - 10272
(2021/08/12)
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- Lewis Acidic Boranes, Lewis Bases, and Equilibrium Constants: A Reliable Scaffold for a Quantitative Lewis Acidity/Basicity Scale
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A quantitative Lewis acidity/basicity scale toward boron-centered Lewis acids has been developed based on a set of 90 experimental equilibrium constants for the reactions of triarylboranes with various O-, N-, S-, and P-centered Lewis bases in dichloromethane at 20 °C. Analysis with the linear free energy relationship log KB=LAB+LBB allows equilibrium constants, KB, to be calculated for any type of borane/Lewis base combination through the sum of two descriptors, one for Lewis acidity (LAB) and one for Lewis basicity (LBB). The resulting Lewis acidity/basicity scale is independent of fixed reference acids/bases and valid for various types of trivalent boron-centered Lewis acids. It is demonstrated that the newly developed Lewis acidity/basicity scale is easily extendable through linear relationships with quantum-chemically calculated or common physical–organic descriptors and known thermodynamic data (ΔH (Formula presented.)). Furthermore, this experimental platform can be utilized for the rational development of borane-catalyzed reactions.
- Mayer, Robert J.,Hampel, Nathalie,Ofial, Armin R.
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supporting information
p. 4070 - 4080
(2021/01/29)
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- -Annulation of pyridinium ylides with 1-chloro-2-nitrostyrenes unveils a tubulin polymerization inhibitor
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Indolizines and pyrazolo[1,5-a]pyridines were prepared via [3 + 2]-cycloaddition of pyridinium ylides to 1-chloro-2-nitrostyrenes. The synthesized molecules were evaluated for antiproliferative activities against a BE(2)-C neuroblastoma cell line with several compounds decreasing the viability of cancer cells. Indolizine 9db showed higher potency than that of all-trans-retinoic acid, an approved cancer drug. Mechanistically, it was found to inhibit tubulin polymerization and it is thus proposed that the discovered chemistry can be exploited for the development of novel microtubule-targeting anticancer agents.
- Aksenov, Alexander V.,Aksenov, Dmitrii A.,Aksenov, nicolai A.,Arutiunov, nikolai A.,Betancourt, Tania,Du, Liqin,Grishin, Igor Yu.,Kirilov, nikita K.,Kornienko, Alexander,Rubin, Michael,Wang, Huifen,pelly, Stephen C.
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p. 7234 - 7245
(2021/08/30)
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- A Lewis Base Nucleofugality Parameter, NFB, and Its Application in an Analysis of MIDA-Boronate Hydrolysis Kinetics
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The kinetics of quinuclidine displacement of BH3 from a wide range of Lewis base borane adducts have been measured. Parameterization of these rates has enabled the development of a nucleofugality scale (NFB), shown to quantify and predict the leaving group ability of a range of other Lewis bases. Additivity observed across a number of series R′3-nRnX (X = P, N; R′ = aryl, alkyl) has allowed the formulation of related substituent parameters (nfPB, nfAB), providing a means of calculating NFB values for a range of Lewis bases that extends far beyond those experimentally derived. The utility of the nucleofugality parameter is explored by the correlation of the substituent parameter nfPB with the hydrolyses rates of a series of alkyl and aryl MIDA boronates under neutral conditions. This has allowed the identification of MIDA boronates with heteroatoms proximal to the reacting center, showing unusual kinetic lability or stability to hydrolysis.
- García-Domínguez, Andrés,Gonzalez, Jorge A.,Leach, Andrew G.,Lloyd-Jones, Guy C.,Nichol, Gary S.,Taylor, Nicholas P.
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supporting information
(2022/01/04)
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- Protodeboronation of (Hetero)Arylboronic Esters: Direct versus Prehydrolytic Pathways and Self-/Auto-Catalysis
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The kinetics and mechanism of the base-catalyzed hydrolysis (ArB(OR)2→ ArB(OH)2) and protodeboronation (ArB(OR)2→ ArH) of a series of boronic esters, encompassing eight different polyols and 10 polyfluoroaryl and heteroaryl moieties, have been investigated by in situ and stopped-flow NMR spectroscopy (19F,1H, and11B), pH-rate dependence, isotope entrainment,2H KIEs, and KS-DFT computations. The study reveals the phenomenological stability of boronic esters under basic aqueous-organic conditions to be highly nuanced. In contrast to common assumption, esterification does not necessarily impart greater stability compared to the corresponding boronic acid. Moreover, hydrolysis of the ester to the boronic acid can be a dominant component of the overall protodeboronation process, augmented by self-, auto-, and oxidative (phenolic) catalysis when the pH is close to the pKaof the boronic acid/ester.
- Hayes, Hannah L. D.,Wei, Ran,Assante, Michele,Geogheghan, Katherine J.,Jin, Na,Tomasi, Simone,Noonan, Gary,Leach, Andrew G.,Lloyd-Jones, Guy C.
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supporting information
p. 14814 - 14826
(2021/09/13)
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- Boron-Containing Organic Diradicaloids: Dynamically Modulating Singlet Diradical Character by Lewis Acid-Base Coordination
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Organic diradicaloids have unique open-shell structures and properties and promising applications in organic electronics and spintronics. Incorporation of heteroatoms is an effective strategy to alter the electronic structures of organic diradicaloids. However, B-containing organic diradicaloids are very challenging due to their high reactivities, which are caused by not only diradical nature but also the B atom. In this article, we report a new kind of organic diradicaloids containing boron atoms. Our strategy is to incorporate planarized triarylboranes to antiaromatic polycyclic hydrocarbons (PHs). We synthesized two isomeric B-containing PHs composed of indenofluorene π-skeletons and two dioxa-bridged triphenylborane moieties. As proved by theoretical and experimental results, both of them have excellent ambient stability and open-shell singlet diradical structures, as well as intriguing magnetic and optoelectronic properties, such as thermally accessible triplet species, reversible multiredox ability, and narrow energy gaps. Notably, they possess sufficient Lewis acidity, which has never been observed for organic diradicaloids. In addition, they can coordinate with Lewis bases to form Lewis adducts, achieving unprecedented dynamic modulations of (anti)aromaticity and thus diradical character of organic diradicaloids.
- Dou, Chuandong,Guo, Jiaxiang,Wang, Yue,Yang, Yue
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supporting information
p. 18272 - 18279
(2021/11/12)
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- H2-Free Selective Dehydroxymethylation of Primary Alcohols over Palladium Nanoparticle Catalysts
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The dehydroxymethylation of primary alcohols is a promising strategy to transform biomass-derived oxygenates into hydrocarbon fuels. In this study, a novel, highly efficient, and reusable heterogeneous catalyst system was established for the H2-free dehydroxymethylation of primary alcohol using cerium oxide-supported palladium nanoparticles (Pd/CeO2). A wide range of aliphatic and aromatic alcohols including biomass-derived alcohols were converted into the corresponding one-carbon shorter hydrocarbons in high yields in the absence of any additives, accompanied by the production of H2 and CO. Pd/CeO2 was easily recovered from the reaction mixture and reused, retaining its high activity, thus, providing a simple and sustainable methodology to produce hydrocarbon fuels from biomass-derived oxygenates.
- Yamaguchi, Sho,Kondo, Hiroki,Uesugi, Kohei,Sakoda, Katsumasa,Jitsukawa, Koichiro,Mitsudome, Takato,Mizugaki, Tomoo
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p. 1135 - 1139
(2020/12/29)
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- Nickel-Catalyzed Electrosynthesis of Aryl and Vinyl Phosphinates
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A mild and useful nickel-catalyzed electrochemical phosphonylation of aryl and vinyl bromides is described. We show that alkyl H-phenylphosphinates can be coupled electrochemically with functionalized aryl and vinyl bromides using very simple conditions (Fe/Ni anode, bench-stable nickel pre-catalyst, undivided cell, galvanostatic electrolysis) to furnish the corresponding aryl and vinyl phosphinates in satisfactory to good yields. Couplings can also be applied to heteroaromatic bromides with some limitations like increased propensity to hydro-dehalogenation.
- Daili, Farah,Ouarti, Abdelhakim,Pinaud, Marine,Kribii, Ibtihal,Sengmany, Stéphane,Le Gall, Erwan,Léonel, Eric
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supporting information
p. 3452 - 3455
(2020/05/25)
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- Can Heteroarenes/Arenes Be Hydrogenated Over Catalytic Pd/C Under Ambient Conditions?
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Hydrogenation of over a dozen aromatic compounds, including both heteroarenes and arenes, over palladium on carbon (Pd/C, 1–100 molpercent) with H2-balloon pressure at room temperature is reported. Analyses using pyridine as a model substrate revealed that acetic acid was the best solvent, as using only 1 molpercent Pd/C provided piperidine quantitatively. Substrate scope analysis and density functional theory calculations indicated that reaction rates are highly dependent on frontier molecular orbital characteristics and the steric bulkiness of substituents. Moreover, the established method was used for the concise synthesis of the anti-Alzheimer drug donepezil (Aricept?).
- Tanaka, Nao,Usuki, Toyonobu
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p. 5514 - 5522
(2020/07/24)
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- A visible-light-photocatalytic water-splitting strategy for sustainable hydrogenation/deuteration of aryl chlorides
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Hydrogenation/deuteration of carbon chloride (C?Cl) bonds is of high significance but remains a remarkable challenge in synthetic chemistry, especially using safe and inexpensive hydrogen donors. In this article, a visible-light-photocatalytic watersplitting hydrogenation technology (WSHT) is proposed to in-situ generate active H-species (i.e., Had) for controllable hydrogenation of aryl chlorides instead of using flammable H2. When applying heavy water-splitting systems, we could selectively install deuterium at the C?Cl position of aryl chlorides under mild conditions for the sustainable synthesis of high-valued added deuterated chemicals. Sub-micrometer Pd nanosheets (Pd NSs) decorated crystallined polymeric carbon nitrides (CPCN) is developed as the bifunctional photocatalyst, whereas Pd NSs not only serve as a cocatalyst of CPCN to generate and stabilize H (D)-species but also play a significant role in the sequential activation and hydrogenation/deuteration of C?Cl bonds. This article highlights a photocatalytic-WSHT for controllable hydrogenation/deuteration of low-cost aryl chlorides, providing a promising way for the photosynthesis of high-valued added chemicals instead of the hydrogen evolution.
- Ling, Xiang,Xu, Yangsen,Wu, Shaoping,Liu, Mofan,Yang, Peng,Qiu, Chuntian,Zhang, Guoqiang,Zhou, Hongwei,Su, Chenliang
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p. 386 - 392
(2020/02/25)
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- Transition-Metal-Free and Visible-Light-Mediated Desulfonylation and Dehalogenation Reactions: Hantzsch Ester Anion as Electron and Hydrogen Atom Donor
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Novel approaches for N- and O-desulfonylation under room temperature (rt) and transition-metal-free conditions have been developed. The first methodology involves the transformation of a variety of N-sulfonyl heterocycles and phenyl benzenesulfonates to the corresponding desulfonylated products in good to excellent yields using only KOtBu in dimethyl sulfoxide (DMSO) at rt. Alternately, a visible light method has been used for deprotection of N-methyl-N-arylsulfonamides with Hantzsch ester (HE) anion serving as the visible-light-absorbing reagent and electron and hydrogen atom donor to promote the desulfonylation reaction. The HE anion can be easily prepared in situ by reaction of the corresponding HE with KOtBu in DMSO at rt. Both protocols were further explored in terms of synthetic scope as well as mechanistic aspects to rationalize key features of desulfonylation processes. Furthermore, the HE anion induces reductive dehalogenation reaction of aryl halides under visible light irradiation.
- Heredia, Micaela D.,Guerra, Walter D.,Barolo, Silvia M.,Fornasier, Santiago J.,Rossi, Roberto A.,Budén, Mariá E.
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p. 13481 - 13494
(2020/12/15)
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- Catalytic Deoxygenation of Amine and Pyridine N-Oxides Using Rhodium PCcarbeneP Pincer Complexes
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Rhodium PCcarbeneP pincer complexes 1-L (L = PPh3, PPh2(C6F5), PCy3) readily facilitate deoxygenation of amine and pyridine N-oxides. The resulting complexes exhibit δ2-C= O coordination of the resulting keto POP pincer ligand. These δ2-Ca? O linkages in the metalloepoxide complexes are readily reduced by isopropyl alcohol and various benzylic alcohols. Thus, efficient catalytic deoxygenation of amine and pyridine N-oxides is possible using complexes 1-L and isopropyl alcohol. This represents a pioneering example of PCcarbeneP pincer complexes being used as catalysts for catalytic deoxygenation.
- Tinnermann, Hendrik,Sung, Simon,Cala, Beatrice A.,Gill, Hashir J.,Young, Rowan D.
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p. 797 - 803
(2020/03/13)
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- The Electronic Properties of Ni(PNN) Pincer Complexes Modulate Activity in Catalytic Hydrodehalogenation Reactions
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Three chloronickel(II) complexes of PNN- pincer ligands with pyrazolyl and diphenylphosphino donors appended to different arms of diarylamido anchors were prepared and fully characterized. The three derivatives (1-OMe, 1-Me, 1-CF3) differ only by the identity of the para-aryl substituent on the pyrazolyl arm with 1-OMe being 310 mV easier to oxidize than 1-CF3. All three complexes are competent catalysts for hydrodehalogenation reactions of 1-bromooctane and a variety of aryl halides in dimethylacetamide using NaBH4 as both base and hydride source. Comparative studies using diverse substrates showed that catalytic activity correlates with electron donor properties; 1-OMe was superior to the other two. Deuterium labeling studies verified NaBD4 as the deuteride source and excluded solvent-assisted radical pathways.
- Wang, Denan,Gardinier, James R.
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p. 4425 - 4434
(2020/10/19)
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- NCP-Type Pincer Iridium Complexes Catalyzed Transfer-Dehydrogenation of Alkanes and Heterocycles?
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A series of NCP-type pincer iridium complexes, (RNCCP)IrHCl (2a—2c) and (BQ-NCOP)IrHCl 3, have been studied for catalytic transfer alkane dehydrogenation. Complex 3 containing a rigid benzoquinoline backbone exhibits high activity and robustness in dehydrogenation of alkanes to form alkenes. Even more importantly, this catalyst system was also highly effective in the dehydrogenation of a wide range of heterocycles to furnish heteroarenes.
- Wang, Yulei,Qian, Lu,Huang, Zhidao,Liu, Guixia,Huang, Zheng
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supporting information
p. 837 - 841
(2020/05/18)
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- Tailorable carbazolyl cyanobenzene-based photocatalysts for visible light-induced reduction of aryl halides
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Herein, a series of carbazolyl cyanobenzene (CCB)-based organic photocatalysts with a broad range of photoredox capabilities were designed and synthesized, allowing precise control of the photocatalytic reactivity for the controllable reduction of aryl halides via a metal-free process. The screened-out CCB (5CzBN), a metal-free, low-cost, scalable and sustainable photocatalyst with both strong oxidative and reductive ability, exhibits superior performance for both dehalogenation and C[sbnd]C bond-forming arylation reactions.
- Ou, Wei,Zou, Ru,Han, Mengting,Yu, Lei,Su, Chenliang
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supporting information
p. 1899 - 1902
(2019/12/27)
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- Synthesis of thioethers, arenes and arylated benzoxazoles by transformation of the C(aryl)-C bond of aryl alcohols
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Transformation of aryl alcohols into high-value functionalized aromatic compounds by selective cleavage and functionalization of the C(aryl)-C(OH) bond is of crucial importance, but very challenging by far. Herein, for the first time, we report a novel and versatile strategy for activation and functionalization of C(aryl)-C(OH) bonds by the cooperation of oxygenation and decarboxylative functionalization. A diverse range of aryl alcohol substrates were employed as arylation reagents via the cleavage of C(aryl)-C(OH) bonds and effectively converted into corresponding thioether, arene, and arylated benzoxazole products in excellent yields, in a Cu based catalytic system using O2 as the oxidant. This study offers a new way for aryl alcohol conversion and potentially offers a new opportunity to produce high-value functionalized aromatics from renewable feedstocks such as lignin which features abundant C(aryl)-C(OH) bonds in its linkages.
- Chen, Bingfeng,Han, Buxing,Liu, Mingyang,Meng, Qinglei,Song, Jinliang,Zhang, Pei,Zhang, Zhanrong
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p. 7634 - 7640
(2020/08/14)
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- Z-Selective Monothiolate Ruthenium Indenylidene Olefin Metathesis Catalysts
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Ru-alkylidenes bearing sterically demanding arylthiolate ligands (SAr) constitute one of only two classes of catalyst that are Z-selective in metathesis of 1-alkenes. Of particular interest are complexes bearing pyridine as a stabilizing donor ligand, [RuCl(SAr)(a? CHR)(NHC)(py)] (R = phenyl or 2-thienyl, NHC = N-heterocyclic carbene, py = pyridine), which initiate catalysis rapidly and give appreciable yields combined with moderate to high Z-selectivity within minutes at room temperature. Here, we extend this chemistry by synthesizing and testing the first two such complexes (5a and 5b) bearing 3-phenylindenylidene, a ligand known to promote stability in other ruthenium-based olefin metathesis catalysts. The steric pressure resulting from the three bulky ligands (the NHC, the arylthiolate, and the indenylidene) forces the thiolate ligand to position itself trans to the NHC ligand, a configuration different from that of the corresponding alkylidenes. Surprisingly, although this configuration is incompatible with Z-selectivity and slows down pyridine dissociation, the two new complexes initiate readily at room temperature. Although their thermal stability is lower than that of typical indenylidene-bearing catalysts, 5a and 5b are fairly stable in catalysis (TONs up to 2200) and offer up to ca. 80% of the Z-isomer in prototypical metathesis homocoupling reactions. Density functional theory (DFT) calculations confirm the energetic cost of dissociating pyridine from 5a (= M1-Py) to generate 14-electron complex M1. Whereas the latter isomer does not give a metathesis-potent allylbenzene ?-complex, it may isomerize to M1-trans and M2, which both form ?-complexes in which the olefin is correctly oriented for cycloaddition. The olefin orientation in these complexes is also indicative of Z-selectivity.
- Smit, Wietse,Ekeli, Jonas B.,Occhipinti, Giovanni,Wo?niak, Bartosz,T?rnroos, Karl W.,Jensen, Vidar R.
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supporting information
p. 397 - 407
(2020/02/13)
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- ELECTRON DONOR, AND METHOD FOR SYNTHESIZING 4, 4'-BIPYRIDINE USING ELECTRON DONOR
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Provided are an electron donor that is easy to handle and can be used to carry out a coupling reaction economically and efficiently through simple operations under mild conditions in a short period of time, and a method for synthesizing 4,4′-bipyridine using the electron donor. The electron donor includes a mixture of a dispersion product obtained by dispersing sodium in a dispersion solvent and 1,3-dimethyl-2-imidazolidinone, and this electron donor is used in the method for synthesizing 4,4′-bipyridine.
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Paragraph 0082-0086
(2020/09/09)
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- Photorelease of Pyridines Using a Metal-Free Photoremovable Protecting Group
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The photorelease of bioactive molecules has emerged as a valuable tool in biochemistry. Nevertheless, many important bioactive molecules, such as pyridine derivatives, cannot benefit from currently available organic photoremovable protecting groups (PPGs). We found that the inefficient photorelease of pyridines is attributed to intramolecular photoinduced electron transfer (PET) from PPGs to pyridinium ions. To alleviate PET, we rationally designed a strategy to drive the excited state of PPG from S1 to T1 with a heavy atom, and synthesized a new PPG by substitution of the H atom at the 3-position of 7-dietheylamino-coumarin-4-methyl (DEACM) with Br or I. This resulted in an improved photolytic efficiency of the pyridinium ion by hundreds-fold in aqueous solution. The PPG can be applied to various pyridine derivatives. The successful photorelease of a microtubule inhibitor, indibulin, in living cells was demonstrated for the potential application of this strategy in biochemical research.
- Dong, Zaizai,Fang, Xiaohong,Kou, Xiaolong,Tan, Weihong,Tang, Xiao-Jun,Wu, Yayun,Zhang, Zhen,Zhao, Rong,Zhou, Wei
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supporting information
p. 18386 - 18389
(2020/08/24)
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- γ-Carboline synthesis enabled by Rh(iii)-catalysed regioselective C-H annulation
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A redox-neutral Rh(iii)-catalyzed C-H annulation of indolyl oximes was developed. Relying on the use of various alkynyl silanes as the terminal alkyne surrogates, the reaction exhibited a reverse regioselectivity, thus giving an exclusive and easy way for the synthesis of a wide range of substituent free γ-carbolines at C3 position with high efficiency. Deuterium-labelling experiments and kinetic analysis have preliminarily shed light on the working mode of this catalytic system. This journal is
- Jiang, Bo,Jia, Jingwen,Sun, Yufei,Wang, Yichun,Zeng, Jing,Bu, Xiubin,Shi, Liangliang,Sun, Xiaoying,Yang, Xiaobo
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supporting information
p. 13389 - 13392
(2020/11/10)
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- Visible-Light-Induced Ni-Catalyzed Radical Borylation of Chloroarenes
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A highly selective and general photoinduced C-Cl borylation protocol that employs [Ni(IMes)2] (IMes = 1,3-dimesitylimidazoline-2-ylidene) for the radical borylation of chloroarenes is reported. This photoinduced system operates with visible light (400 nm) and achieves borylation of a wide range of chloroarenes with B2pin2 at room temperature in excellent yields and with high selectivity, thereby demonstrating its broad utility and functional group tolerance. Mechanistic investigations suggest that the borylation reactions proceed via a radical process. EPR studies demonstrate that [Ni(IMes)2] undergoes very fast chlorine atom abstraction from aryl chlorides to give [NiI(IMes)2Cl] and aryl radicals. Control experiments indicate that light promotes the reaction of [NiI(IMes)2Cl] with aryl chlorides generating additional aryl radicals and [NiII(IMes)2Cl2]. The aryl radicals react with an anionic sp2-sp3 diborane [B2pin2(OMe)]- formed from B2pin2 and KOMe to yield the corresponding borylation product and the [Bpin(OMe)]?- radical anion, which reduces [NiII(IMes)2Cl2] under irradiation to regenerate [NiI(IMes)2Cl] and [Ni(IMes)2] for the next catalytic cycle.
- Tian, Ya-Ming,Guo, Xiao-Ning,Krummenacher, Ivo,Wu, Zhu,Nitsch, J?rn,Braunschweig, Holger,Radius, Udo,Marder, Todd B.
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supporting information
p. 18231 - 18242
(2020/11/02)
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- Two-State Reactivity in Iron-Catalyzed Alkene Isomerization Confers σ-Base Resistance
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A low-coordinate, high spin (S = 3/2) organometallic iron(I) complex is a catalyst for the isomerization of alkenes. A combination of experimental and computational mechanistic studies supports a mechanism in which alkene isomerization occurs by the allyl mechanism. Importantly, while substrate binding occurs on the S = 3/2 surface, oxidative addition to an η1-allyl intermediate only occurs on the S = 1/2 surface. Since this spin state change is only possible when the alkene substrate is bound, the catalyst has high immunity to typical σ-base poisons due to the antibonding interactions of the high spin state.
- Lutz, Sean A.,Hickey, Anne K.,Gao, Yafei,Chen, Chun-Hsing,Smith, Jeremy M.
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supporting information
p. 15527 - 15535
(2020/10/20)
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- Efficient Chemoselective Reduction of N-Oxides and Sulfoxides Using a Carbon-Supported Molybdenum-Dioxo Catalyst and Alcohol
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The chemoselective reduction of a wide range of N-oxides and sulfoxides with alcohols is achieved using a carbon-supported dioxo-molybdenum (Mo@C) catalyst. Of the 10 alcohols screened, benzyl alcohol exhibits the highest reduction efficiency. A variety of N-oxide and both aromatic and aliphatic sulfoxide substrates bearing halogens as well as additional reducible functionalities are efficiently and chemoselectively reduced with benzyl alcohol. Chemoselective N-oxide reduction is effected even in the presence of potentially competing sulfoxide moieties. In addition, the Mo@C catalyst is air- and moisture-stable, and is easily separated from the reaction mixture and then re-subjected to reaction conditions over multiple cycles without significant reactivity or selectivity degradation. The high stability and recyclability of the catalyst, paired with its low toxicity and use of earth-abundant elements makes it an environmentally friendly catalytic system.
- Li, Jiaqi,Liu, Shengsi,Lohr, Tracy L.,Marks, Tobin J.
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p. 4139 - 4146
(2019/05/27)
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- Continuous-flow Synthesis of Aryl Aldehydes by Pd-catalyzed Formylation of Aryl Bromides Using Carbon Monoxide and Hydrogen
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A continuous-flow protocol utilizing syngas (CO and H2) was developed for the palladium-catalyzed reductive carbonylation of (hetero)aryl bromides to their corresponding (hetero)aryl aldehydes. The optimization of temperature, pressure, catalyst and ligand loading, and residence time resulted in process-intensified flow conditions for the transformation. In addition, a key benefit of investigating the reaction in flow is the ability to precisely control the CO-to-H2 stoichiometric ratio, which was identified as having a critical influence on yield. The protocol proceeds with low catalyst and ligand loadings: palladium acetate (1 mol % or below) and cataCXium A (3 mol % or below). A variety of (hetero)aryl bromides at a 3 mmol scale were converted to their corresponding (hetero)aryl aldehydes at 12 bar pressure (CO/H2=1:3) and 120 °C reaction temperature within 45 min residence time to afford products mostly in good-to-excellent yields (17 examples). In particular, a successful scale-up was achieved over 415 min operation time for the reductive carbonylation of 2-bromo-6-methoxynaphthalene to synthesize 3.8 g of 6-methoxy-2-naphthaldehyde in 85 % isolated yield. Studies were conducted to understand catalyst decomposition within the reactor by using inductively coupled plasma–mass spectrometry (ICP–MS) analysis. The palladium could easily be recovered using an aqueous nitric acid wash post reaction. Mechanistic aspects and the scope of the transformation are discussed.
- Hone, Christopher A.,Lopatka, Pavol,Munday, Rachel,O'Kearney-McMullan, Anne,Kappe, C. Oliver
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p. 326 - 337
(2018/11/23)
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- Implementing Hydrogen Atom Transfer (HAT) Catalysis for Rapid and Selective Reductive Photoredox Transformations in Continuous Flow
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The reductive transformation of aryl halides and carbonyl compounds is a key step in many photoredox transformations. By combining a highly reducing organic photocatalyst with a thiol hydrogen atom transfer (HAT) catalyst, we showcase rapid and highly selective reactions of these synthetically important starting materials in continuous flow. The fast reduction of aryl iodides, bromides and chlorides has been demonstrated with residence times in some cases below one minute. Selectivity between mono- and di-dehalogenation could also be achieved in some cases. Aryl ketones, aldehydes and imines were shown to undergo facile pinacol couplings, and the coupling of an aryl chloride with a styrene was also successful.
- Steiner, Alexander,Williams, Jason D.,Rincón, Juan A,de Frutos, Oscar,Mateos, Carlos,Kappe, C. Oliver
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supporting information
p. 5807 - 5811
(2019/08/01)
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- Heterogeneously palladium-catalyzed acceptorless dehydrogenative aromatization of cyclic amines
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In this manuscript, we report an efficient heterogeneously catalyzed acceptorless dehydrogenative aromatization of cyclic amines under relatively mild conditions. In the presence of a supported catalyst Pd/LDH (LDH = layered double hydroxide), various kinds of structurally diverse cyclic amines including piperidines, tetrahydro(iso)quinolines, and indolines could be converted into the corresponding heteroarenes. Pd/LDH could be reused several times though its catalytic activity gradually declined due to the increase in the palladium particle size.
- Oyama, Takashi,Yatabe, Takafumi,Jin, Xiongjie,Mizuno, Noritaka,Yamaguchi, Kazuya
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supporting information
p. 517 - 520
(2019/06/11)
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- ZEOLITE CATALYST
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The present disclosure relates to the preparation of pyridine derivatives, such as α-picoline or α-parvoline, and catalysts useful for the selective preparation of such pyridine derivatives. Particularly, the present disclosure relates to the selective preparation of certain pyridine derivative using dealuminated zeolite catalysts.
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Paragraph 0128; 0130
(2019/05/22)
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- Involving Single-Atom Silver(0) in Selective Dehalogenation by AgF under Visible-Light Irradiation
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The dehalogenation-arylation and the hydrodehalogenation of various types of organic halides are selectively realized using AgF and visible light without any organic additives under mild conditions. Single-atom silver(0) (denoted as SAAg) serves as the catalytically active center, and the TOF of SAAg reaches 6000 h-1. This elusive activity of Ag is beyond that expected from its ionic, nano, or bulk forms.
- Wu, Wenli,Cui, Enxin,Zhang, Yun,Zhang, Chen,Zhu, Feng,Tung, Chen-Ho,Wang, Yifeng
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p. 6335 - 6341
(2019/07/04)
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- Axial coordination reactions with nitrogenous bases and determination of equilibrium constants for zinc tetraarylporphyrins containing four β, β ′-fused butano and benzo groups in nonaqueous media
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The axial coordination properties of six zinc tetraarylporphyrins with seven different nitrogenous bases were examined in CH2Cl2 for derivatives containing four β,β′-fused butano or benzo groups and the equilibrium constants (logK) determined using spectral titration methods. The examined compounds are represented as butano(YPh)4PorZn and benzo(YPh)4PorZn, where Por is the porphyrin dianion and Y is a CH3, H or Cl substituent on the para-position of each meso-phenyl ring of the macrocycle. The initial four-coordinate butano-And benzoporphyrins will axially bind one nitrogenous base to form five-coordinate derivatives in CH2Cl2 and this leads to a 4-22 nm red-shift of the Soret and Q bands. The logK values range from 1.98 to 4.69 for butano(YPh)4PorZn and from 3.42 to 5.36 for benzo(YPh)4PorZn, with the exact value depending upon the meso and β-substituents of the porphyrin and the conjugate acid dissociation constants (pKa) of the nitrogenous base.
- Ye, Lina,Fang, Yuanyuan,Ou, Zhongping,Wang, Liping,Xue, Songlin,Lu, Yang,Kadish, Karl M.
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p. 196 - 206
(2019/02/19)
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- Flow hydrodediazoniation of aromatic heterocycles
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Continuous flow processing was applied for the rapid replacement of an aromatic amino group with a hydride. The approach was applied to a range of aromatic heterocycles, confirming the wide scope and substituent-tolerance of the processes. Flow equipment was utilized and the process optimised to overcome the problematically-unstable intermediates that have restricted yields in previous studies relying on batch procedures. Various common organic solvents were investigated as potential hydride sources. The approach has allowed key structures, such as amino-pyrazoles and aminopyridines, to be deaminated in good yield using a purely organic-soluble system.
- R?der, Liesa,Nicholls, Alexander J.,Baxendale, Ian R.
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- Photocatalytic reaction of 4-cyanopyridine with tertiary amines
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[Figure not available: see fulltext.] The reaction of 4-cyanopyridine with tertiary aliphatic amines photocatalyzed by fac-tris[2-phenylpyridinato-C2,N]iridium(III) complex was studied. The reactions led to arylation of the α-C–H bond of the amine to form the corresponding pyridin-4-yl derivatives along with unsubstituted pyridine.
- Vorob’ev, Aleksey Yu.
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- Electrochemical dehydrogenation of hydrazines to azo compounds
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A strategy for the electrochemical dehydrogenation of hydrazine compounds is disclosed under ambient conditions. This protocol proceeded smoothly in ethanol by employing electrons as clean oxidants. Its synthetic value is well demonstrated by the highly efficient synthesis of symmetric and unsymmetric azo compounds. It is an environmentally friendly transformation and the present protocol was effective on a large scale.
- Du, Ke-Si,Huang, Jing-Mei
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supporting information
p. 1680 - 1685
(2019/04/08)
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- Catalytic reduction of aryl trialkylammonium salts to aryl silanes and arenes
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A new approach for the reduction of aryl ammonium salts to arenes or aryl silanes using nickel catalysis is reported. This method displays excellent ligand-controlled selectivity based on the N-heterocyclic carbene (NHC) ligand employed. Utilizing a large NHC in non-polar solvents generates aryl silanes, while small NHCs in polar solvents promote reduction to arenes. Several classes of aryl silanes can be accessed from simple aniline building blocks, including those useful for cross-couplings, oxidations, and halogenations. The reaction conditions are mild, functional group tolerant, and provide efficient access to a variety of benzene derivatives.
- Rand, Alexander W.,Montgomery, John
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p. 5338 - 5344
(2019/05/29)
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- Thermal Behavior Analysis of Two Synthesized Flavor Precursors of N-alkylpyrrole Derivatives
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To expand the library of pyrrole-containing flavor precursors, two new flavor precursors—methyl N-benzyl-2-methyl-5-formylpyrrole-3-carboxylate (NBMF) and methyl N-butyl-2-methyl-5-formylpyrrole-3-carboxylate (NUMF)—were synthesized by cyclization, oxidation, and alkylation reactions. Thermogravimetry (TG), differential scanning calorimeter, and pyrolysis–gas chromatography/mass spectrometry were utilized to analyze the thermal degradation behavior and thermal degradation products of NBMF and NUMF. The TG-DTG curve indicated that the maximum mass loss rates of NBMF and NUMF appear at 310 and 268°C, respectively. The largest peaks of NBMF and NUMF showed by the differential scanning calorimeter curve were 315 and 274°C, respectively. Pyrolysis–gas chromatography/mass spectrometry detected small molecule fragrance compounds appeared during thermal degradation, such as 2-methylpyrrole, 1-methylpyrrole-2-carboxylic acid methyl ester, limonene, and methyl formate. Finally, the thermal degradation mechanism of NBMF and NUMF was discussed, which provided a theoretical basis for their application in tobacco flavoring additives.
- Ai, Lvye,Liu, Mengzhen,Ji, Xiaoming,Lai, Miao,Zhao, Mingqin,Ren, Tianbao
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p. 2389 - 2397
(2019/08/01)
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- The one-pot synthesis of pyridine derivatives from the corresponding 1,5-dicarbonyl compounds
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The optimization of the one-pot, acid-promoted synthesis of pyridine and alkylpyridine derivatives from simple alkyl-1,5-dicarbonyl derivatives and via the corresponding oxime intermediate is described. Of all the combinations of and solvents tested, the use of HCl in refluxing dioxane was found to result in the highest chemical yields. Twelve pyridines were prepared using this method.
- Mihara, Hiromichi,Miyakoshi, Takeru,Kikuchi, Yui,Konno, Hiroyuki
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p. 1375 - 1383
(2019/12/23)
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- Mesoporous Aluminosilicates in the Synthesis of N-Heterocyclic Compounds
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Abstract: The catalytic properties of samples of amorphous mesoporous aluminosilicate ASM with different Si/Al molar ratios (40, 80, 160) were studied in the synthesis of practically important pyridines (by the interaction of С2–С5 alcohols with formaldehyde and ammonia, cyclocondensation of acetaldehyde and propionic aldehyde with ammonia), dialkylquinolines and alkyltetrahydroquinolines (by reaction of aniline with C3, C4 aldehydes) and alkyldihydroquinolines (by interaction of aniline with ketones, acetone and acetophenone). It is found that mesoporous aluminosilicate ASM sample with a molar ratio of Si/Al = 40, which has the highest acidity among the studied samples, exhibits the highest activity and selectivity in these reactions.
- Agliullin, M. R.,Bikbaeva, V. R.,Bubennov, S. V.,Filippova, N. A.,Gataulin, A. R.,Grigor’eva, N. G.,Kostyleva, S. A.,Kutepov, B. I.,Narender, Nama
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p. 733 - 743
(2020/02/25)
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- Synthesis, structural characterization, and coordination chemistry of (Trineopentylphosphine)palladium(aryl)bromide dimer complexes ([(Np3P)Pd(Ar)Br]2)
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A series of [(PNp3)Pd(Ar)Br]2 complexes (PNp3 = trineopentylphosphine, Ar = 4-tolyl, 4-tert-butylphenyl, 2-tolyl, 4-methoxy-2-methylphenyl, 2-isopropylphenyl, and 2,6-dimethylphenyl) were synthesized and structurally characterized by X-ray crystallography and density functional theory optimized structures. The trineopentylphosphine ligand is able to accommodate coordination of other sterically demanding ligands through changes in its conformation. These conformational changes can be seen in changes in percent buried volume of the PNp3 ligand. The binding equilibria of the [(PNp3)Pd(Ar)Br]2 complexes with pyridine derivatives were determined experimentally and analyzed computationally. The binding equilibria are sensitive to the steric demand of the pyridine ligand and less sensitive to the steric demand of the aryl ligand on palladium. In contrast to previous studies, the binding equilibria do not correlate with pyridine basicity. The binding equilibria results are relevant to fundamental ligand coordination steps in cross-coupling reactions, such as Buchwald-Hartwig aminations.
- Hu, Huaiyuan,Vasiliu, Monica,Stein, Trent H.,Qu, Fengrui,Gerlach, Deidra L.,Dixon, David A.,Shaughnessy, Kevin H.
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supporting information
p. 13299 - 13313
(2019/10/11)
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- Metal-Free Decarboxylative Alkoxylation of 2-Picolinic Acid and Its Derivatives with Cyclic Ethers: One Step Construction of C-O and C-Cl Bonds
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A new strategy for the metal-free decarboxylative alkoxylation of 2-picolinic acid and its derivatives is described. The three-component reaction of 2-picolinic acid or its derivatives, cyclic ethers, and tBuOCl proceeded smoothly in the presence of a catalytic amount of p-chloranil to produce 2-alkoxylated pyridines with an ω -chlorine atom in satisfactory to excellent yields. New C-O and C-Cl bonds were generated in one step. The ω-C-Cl bond can be easily transformed to a C-C or C-heteroatom bond, increasing the use of 2-alkoxylated pyridine products in organic synthesis. The electronic property of the substituent linked on the pyridine ring did not influence the reactivity of the 2-picolinic acid substrates.
- Yu, Xiaoqiang,He, Min,Wu, Jianglin,Zhou, Chuancheng,Feng, Xiujuan,Yamamoto, Yoshinori,Bao, Ming
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supporting information
p. 6780 - 6784
(2018/10/24)
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- Application of Silicon-Initiated Water Splitting for the Reduction of Organic Substrates
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The use of water as a donor for hydrogen suitable for the reduction of several important classes of organic compounds is described. It is found that the reductive water splitting can be promoted by several metalloids among which silicon shows the best efficiency. The developed methodologies were applied for the reduction of nitro compounds, N-oxides, sulfoxides, alkenes, alkynes, hydrodehalogenation as well as for the gram-scale synthesis of several substrates of industrial importance.
- Gevorgyan, Ashot,Mkrtchyan, Satenik,Grigoryan, Tatevik,Iaroshenko, Viktor O.
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p. 375 - 382
(2018/06/04)
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- Hydrodehalogenation of Polyhalogenated Aromatics Catalyzed by NiPd Nanoparticles Supported on Nitrogen-Doped Graphene
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Ni30Pd70 nanoparticles supported on nitrogen-doped graphene (NG) acts as a catalyst for the hydrodehalogenation of halogenated aromatics under mild reaction conditions. It reduces mono- or dichloroarenes to the corresponding dehalogenated arenes in >90 % yield in 10 % aqueous isopropanol solvent at or below 50 °C within 5 h. Tests on a variety of substrates containing various functional groups show that the catalyst is selective for reduction of C?Cl and C?Br bonds. In addition, this catalyst completely hydrodehalogenates high-concentration solutions of dioxin, polychlorinated biphenyls, chloroaromatic constituents of the defoliant agent orange, and polybrominated diphenyl ethers in 12 h. The catalyst is reusable and shows no morphological or compositional changes after 5 cycles. This methodology offers a powerful, low-cost, and safe technology for the degradation of polyhalogenated aromatics, and may be useful for preventing proliferation of these toxins in the environment from causing serious health issues.
- Guo, Xuefeng,Yu, Chao,Yin, Zhouyang,Sun, Shouheng,Seto, Christopher T.
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p. 1617 - 1620
(2018/06/15)
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