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Reaction of NacNacGa with phenylisocyante generates a transient species amenable to unusual 1,3-C–H bond addition of unactivated sp3 C–H and sp2 C–H bonds of substrates featuring a hard donor atom. This reaction proceeds for pyridine oxide, dimethylsulfoxide, and dimethylacetamide, but not for pyridine, cyclohexanone, and ethyl acetate. C–H activation was also not observed for reactions with triethylphosphine oxide but, interestingly, in the presence of this compound isocyanate undergoes self-coupling on Ga(I) with a regioselectivity that is different when carried out in the absence of Et3PO. [ABSTRACT FROM AUTHOR]

Oxidation of a base‐stabilized phosphinidene (κ2‐NNP)P (12, NNP=phosphinoamidinate) with N2O afforded a labile phosphinidene oxide (κ2‐NNP)P=O (16) which was characterized by NMR spectroscopy. Further oxidation of 16 by N2O or reaction of 12 with two equivalents of pyridine oxide afforded the isolable dioxide (κ2‐NNP)PO2 which was characterized by NMR and SC XRD. Trapping of 16 with tolyl isocyanate resulted in P=O/N=C metathesis, eventually affording a urea‐ligated phosphine (κ1‐NNP)P(NTol)2C=O (17) The mechanism of this reaction was elucidated by DFT calculations. Reactions of phosphinidene 12 with azides generated transient imines (NNP)P=NR, which in the case of R=Tol underwent cycloaddition with tolyl Isocyanate to afford the urea product 17, and in the case of R=SiMe3 reacts with N3SiMe3 via the addition of N−Si across the P=N bond affording, after the extrusion of dinitrogen, a P,N‐heterocyclic compound. Both products of the reactions with azides have been fully characterized, both in solution and the solid‐state. Finally, reaction of phosphinidene 12 with one equivalent of sulfur resulted in the isolation of the base‐stabilized phosphinidene sulfide (κ2‐NNP)P=S that has also been fully characterized. [ABSTRACT FROM AUTHOR]

An amine-free sulfonylation of various alcohols was developed that uses 4-methylpyridine N -oxide in the presence of 4Å molecular sieves at room temperature. This mild method gives various sulfonylated products in high yields, and can be applied to base-sensitive substrates. [ABSTRACT FROM AUTHOR]

In aqueous acetate buffer media (pH=4.0-5.2), reaction between the superoxo complex, [(dien)(en)CoIII(O2)CoIII (en) (dien)]5+ (1) and pyridine N-oxide (C5H5NO) proceeds through a complex kinetic pathway and the change of the absorbance of 1 with time also follows a complex pattern. Only in the presence of Ellman's reagent (5,5'-dithio-bis-(2-nitrobenzoic acid), DTNB), the reaction becomes quantitative and each mole of 1 is reduced by one mole of pyridine Noxide (C5H5NO) to produce the corresponding hydroperoxo complex, [(dien)(en)CoIII (HO2)CoIII(en)(dien)]5+ (2), following proton coupled electron transfer (PCET) path. In presence of DTNB, with large excess of pyridine N-oxide (C5H5NO) over [1], the reaction follows first-order kinetics and the observed rate constant, ko increase linearly with increase in [C5H5NO] but decreases with increase in [H+]. It is also noticed that the reaction rate significantly decreases with increasing proportion of D2O replacing H2O in the solvent. Therefore, an H-atom transfer (HAT) from the reducing species to the bridging superoxide in 1 seems reasonable at the rate determining step. Indeed the present work confesses the forthcoming involvement of Ellman's reagent as a radical scavenger. [ABSTRACT FROM AUTHOR]

Summary: Activated carbon materials doped with different nitrogen contents and nitrogen functional groups were synthesized. Nitrogen doping can improve the electrochemical hydrogen storage activity as well as the hydrophilicity of the carbon materials. Synthesized with the optimal synthesis conditions, the N‐doped activate carbon demonstrated the hydrogen storage capacity of 148.4 mAh g−1 under 100 mA g−1 rate, and 84.3% capacity retention at a high current density of 1000 mA g−1. 73.4% hydrogen could be preserved after a 24 hours rest at open potential. The main nitrogen functional groups on this carbon material were found to be pyrrole N, pyridine N oxide and nitro N. The density functional theory (DFT) calculations revealed that the H adsorption energy on pyridine N and pyrrole N was larger than that of pyridine N, while graphite N had no advantage in improving the H adsorption energy of carbon materials. [ABSTRACT FROM AUTHOR]

The first vacuum-ultraviolet absorption spectrum of pyridine-N-oxide has been obtained, and has led to the identification of nearly 30 Rydberg states. These states were identified by use of the vibrational envelope ('footprint') of the UV-photoelectron spectrum, and are based on the first to the third ionization energies (IE). The adiabatic IE order, central to the Rydberg state symmetry identification, is confirmed by multi-configuration SCF calculations as: 12B1 < 12B2 < 12A2 < 22B1. Several excited valence state equilibrium structures were determined by multi-configuration SCF and coupled cluster procedures. Multi-reference multi-root CI was used to calculate both Rydberg and valence state vertical excitation energies and oscillator strengths, which were correlated with the experimental measurements. [ABSTRACT FROM AUTHOR]

The title compound 2,2′-bipyridin-1′-ium 1-oxide bromide crystallizes as a monohydrate, C10H9N2+·Br−·H2O. Structural disorder is observed due to the fact that protonation, as well as oxidation, of the N atoms of 2,2′-bipyridine occurs at either of the N atoms. The disorder extends to the remainder of the cation, with a refined occupancy rate of 0.717 (4) for the major moiety. An intramolecular N—H...O hydrogen bond forces the bipyridine unit into an s-cis conformation. Each pair of neighbouring 2,2′-bipyridin-1′-ium ions forms a dimeric aggregate by hydrogen bonds between their respective N—O and the N—H functions. These dimers and hydrogen-bonding interactions with bromide ions and the water molecule give rise to a complex supramolecular arrangement.

In an ongoing study of the products formed on pyrolysis of chitin (4) under a range of conditions, we now detail the isolation and characterisation of the crystalline and hitherto undetected pyridine N -oxide 18 and enamide 19. Pathways for the formation of these products have been proposed and subjected to both experimental and computational assessment. Two new, small molecule pyrolysis products, 18 and 19 , derived from acid-treated chitin (4) are reported. [ABSTRACT FROM AUTHOR]

Pyridine is an emerging contaminant in groundwater which can adversely affect human health and the electrochemical method has been a paramount method to address it. The present study investigated the degradation of pyridine with Ti/RuO2 anode and Cu-Zn cathode which were combined with a wire entanglement in an undivided catalysis cell, and the system was enhanced by an iron net. First, the enhancement of iron net on electrochemical degradation of pyridine was studied by comparing the presence and absence of iron net. Then, the influencing factors of the electro-iron system, including current density, NaCl dosage and plate distance was studied and Box–Behnken design was employed to investigate the interaction of the three parameters (current density, plate distance, and supporting electrolyte dosage) on the removal of pyridine. Moreover, the electrochemical enhanced pyridine degradation mechanism by iron net was analyzed with cyclic voltammetry (CV) analysis. The reaction pathway and intermediates of pyridine oxidation were also described. It was found that the degradation efficiency of pyridine in the electrochemical system could be increased by 11.3% by adding an iron net. Based on the response surface methodology analysis, the pyridine removal efficiency of 90.2% was achieved under the optimal conditions with a current density of 99.45 mA cm–2, plate distance of 2.99 cm and NaCl dosage of 8.78 g L–1. The CV curve found that the electrochemical oxidation of pyridine was accomplished by indirect oxidation. Pyridine reacts with the oxide formed by Cl– to form intermediates of small organic acid, which can be further mineralized to be CO2 and H2O. Adding an iron net can reduce hydrogen by electrochemical corrosion and reduce the carbonyl group of the intermediate product to hydroxyl group, thereby promoting the degradation of pyridine. This study provides a potentially efficient method for disposing of wastewater pollution caused by pyridine. [ABSTRACT FROM AUTHOR]

The oxorhenium(V) monomer (CH 3 Re(V)O(edt)(Im) (where edt = 1,2 ethanedithiolate, Im= Imidazole) catalyzes the oxygen atom transfer reaction from pyridine N-oxide and substituted pyridine N-oxide to triphenylarsine (Ph 3 As). The kinetic results have shown that the reaction rate is first order with respect to the catalyst and pyridine N-oxide concentrations, and first order with respect to [Ph 3 As] at low concentration and zero order at high [Ph 3 As]. Also, the reaction is zero order with respect to the imidazole concentration. Therefore, rate law is R = k [ Re -Im] [PyNO][Ph 3 As] at low Ph 3 As concentration and the rate law is R = k [ Re -Im] [PyNO] at high Ph 3 As concentration. The electronic effect of the oxidant was investigated by studying the reaction rate constants of different substituted pyridine N Oxide. The correlation of the rate constant values with σ is linear with reaction constant ρ = -2.4. A negative value indicates that the rate increases with electron-donating substituents. The effect of electron donor substituent on the reaction rate is mainly due to the enhancement of the binding of pyridine N-oxide to the ReVO in the first step of the proposed mechanism. The oxidation of ReVO to ReVIIO 2 and release of the pyridine step is not highly sensitive to the nature of the substituent on the pyridine. The computational study indicates that the oxidation of ReVO to ReVIIO 2 and release of the pyridine step is insensitive to the nature of the substituent on the pyridine with the average estimated activation barrier ≈ 9 kcal/mol and its less than the estimated activation barrier in the absence of imidazole (≈ 11.5 kcal/mol). This result support that the imidazole act as nucleophile to assist the oxidation of ReVO to ReVIIO 2 step. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] Two divergent synthetic routes were developed to synthesize cyclopentenyl- & 1,5-divinyl-ketones through gold catalyzed reaction of 1,3-enynes with different types of olefins with the addition of pyridine N- oxide. A formal [3 + 2] cycloaddition occurred in the reaction of aryl olefins by using 1,3-enynes as the C3 reactants, while the C1 reactivity thereof was exhibited in the reaction with alkyl olefins to provide 1,5-divinyl ketone products. [ABSTRACT FROM AUTHOR]

In situ oxidation of the GaI compound NacNacGa by either N2O or pyridine oxide results in the generation of a labile monomeric oxide, NacNacGa(O), which can easily cleave the C−H bonds of aliphatic and aromatic substrates featuring good donor sites. The products of this reaction are gallium organyl hydroxides. DFT calculations show that these reactions start with the formation of NacNac‐Ga(O)(L) adducts, the oxo ligand of which can easily abstract protons from nearby C−H bonds, even for sp2‐hybridized carbon centers. Aliphatic amines do not enter this reaction for kinetic reasons, presumably because of the unfavorable sterics. [ABSTRACT FROM AUTHOR]

Imidazopyridines can exist in several tautomeric forms such as benzimidazole or purine condensed systems. Regioselectivities were determined for N -alkylations of 2-(3,4-dimethoxyphenyl)- imidazopyridines and their 4 and 5-oxides (2 – 4 , 13 , 14) with n -butyl and 4-fluorobenzyl bromides under basic conditions (K 2 CO 3 in DMF). It was observed that N -4 (5 – 8) and N -5 (15 – 17) regioisomers were mainly formed. Compounds 7 (N 4) and 7a (N 1) were separated from the mixtures of regioisomers in a 50 : 1 ratio. Their structural assignments were made with the use of two-dimensional 1H-1H NOE (nuclear overhauser effect spectroscopy [NOESY]) enhancements between the N -CH 2 and protons on the C-4, 5, 6, and 7 positions of the pyridine moiety. To verify the NOESY data, synthesis of compounds 7a and 7b was achieved by the selective method. Complementary structural information was provided by 2D-HMBC spectra of the compounds. Image 1 • N -benzylation of imidazo[4,5- b ]pyridine 4-oxide under basic condition in DMF afforded the mix of N -4 and N- 1,3 regiosomers. • N -benzylation of imidazo[4,5- c ]pyridine 5-oxide under basic condition in DMF afforded only N- 5 regiosomers. • NOESY experiment is the best available method for the structural elucidation of these regioisomers. • HMBC experiment could be effective for assignment of the regisomers as alternative way. [ABSTRACT FROM AUTHOR]

We present magnetic field-dependent specific heat (C) data for [Cu(pyO)6](NO3)2 (pyO = pyridine oxide) (CPN), a molecular salt shown to be quasi-1D, and for a quasi-2D analogue, [Cu(pyO)6](BF4)2 (CPB). For CPN, a sharp feature indicating 3D ordering is observed at 0.16K in zero-field. As the field, H, is increased, the ordering temperature first increases, as expected for quasi-1D antiferromagnets, before decreasing rapidly for H above 3T. The field also transfers the entropy of short-range ordering (SRO) in the spin chains into the 3D ordering peak. At our lowest accessible temperature, T ∼ 0.096K, C/T exhibits an enhanced peak at the critical field. Qualitatively similar behavior is found in CPB. These results demonstrate a potentially powerful new materials route to study quantum phase transitions. [ABSTRACT FROM AUTHOR]

A novel method for the palladium‐catalyzed decarboxylative ortho C–H bond arylation of pyridine 1‐oxides and anilides with benzoic acids as aryl sources is described. The established methodology provides a direct approach for the synthesis of 2‐arylpyridine 1‐oxides and 2‐aryl anilides in good isolated yields. A novel method for palladium‐catalyzed decarboxylative ortho C–H bond arylation of pyridine 1‐oxides and anilides with benzoic acids as aryl sources are described. [ABSTRACT FROM AUTHOR]

This work focuses on the application of dicobalt octacarbonyl (Co2(CO)8) as a metal precursor in the chemistry of formally low-valent cobalt with redox-active bis(imino)pyridine [NNN] ligands. The reactions of both mononucleating mesityl-substituted bis(aldimino)pyridine (L1) and dinucleating macrocyclic xanthene-bridged di(bis(aldimino)pyridine) (L2) with Co2(CO)8 were investigated. Independent of the metal-to-ligand ratio (1 : 1 or 1 : 2 ligand to Co2(CO)8), the reaction of the dinucleating ligand L2 with Co2(CO)8 produces a tetranuclear complex [Co4(L2)(CO)10] featuring two discrete [Co2[NNN](CO)5] units. In contrast, a related mononucleating bis(aldimino)pyridine ligand, L1, produces different species at different ligand to Co2(CO)8 ratios, including dinuclear [Co2(CO)5(L1)] and zwitterionic [Co(L1)2][Co(CO)4]. Interestingly, [Co4(L2)(CO)10] features metal–metal bonds, and no bridging carbonyls, whereas [Co2(CO)5(L1)] contains cobalt centers bridged by one or two carbonyl ligands. In either case, treatment with excess acetonitrile leads to disproportionation to the zwitterionic [Co[NNN](NCMe)2][Co(CO)4] units. The electronic structures of the complexes described above were studied with density functional theory. All the obtained bis(imino)pyridine complexes serve as catalysts for cyclotrimerization of methyl propiolate, albeit their reactivity is inferior compared with Co2(CO)8. [ABSTRACT FROM AUTHOR]

Three M(II)-coordination polymers (M Zn(II), Mn(II)) were synthesized based on a pyridine N -oxide bridging ligand 3,5-bis(4-carboxylphenyl)-pyridine N -oxide ( L1 ). Compounds 1–3 all have novel complicated structures. Compound 1 (Zn( L1 ) 2 (H 2 O) 2 ) and 2 (Zn 2 ( L1 ) 2 (H 2 O) 2 ) are two single crystals obtained in “one pot” and 1 features 1D double chains motif and 2 features 3D network structure. Compound 3 shows 3D network structure with triangular tunnels. The thermogravimetric analyses and photoluminescence properties were also used to investigate the title compounds. [ABSTRACT FROM AUTHOR]

The kinetic inertness of Mn2+ complexes is an important parameter for the in vivo safety of potential MRI contrast agents. Rigidifying the ligand structure typically leads to reinforced kinetic inertness. In this context, we studied the Mn2+ complexes of three linear poly(amino carboxylate) ligands containing a pyridine moiety in their skeleton and bearing four (L1, L2) or three carboxylates (L3). The thermodynamic stability constants of the complexes formed with Mn2+, Ca2+, Mg2+, Zn2+ and Cu2+ have been determined using pH-potentiometry, 1H relaxometry and UV/Vis spectrophotometry and are close to those of the EDTA analogues. In contrast, and despite the presence of the pyridine in the ligand backbone, the dissociation rates of the complexes are several orders of magnitude higher than that of [Mn(EDTA)]2−, resulting from a very efficient dissociation pathway catalyzed by the direct attack of Cu2+ or Cu(OH)+. Due to the fewer carboxylate functions, ligand L3 is less favorable for metal-assisted dissociation and provides higher kinetic inertness for its Mn2+ chelate than the L1 and L2 analogues. The water exchange of the monohydrated MnL3 complex has been studied in a variable temperature 17O NMR study. The exchange rate is very high, k298ex = 2.8 × 109 s−1, which is among the highest values reported for a Mn2+ complex. The NMRD profiles are typical of small molecular weight Mn2+ chelates (r1p = 2.44 mM−1 s−1 at 25 °C and 20 MHz). [ABSTRACT FROM AUTHOR]

The first nickel-catalyzed C H trifluoromethylation of pyridine N -oxides with Togni’s reagent has been achieved. Trifluoromethylation proceeds smoothly under mild conditions with moderate functional group compatibility. Notable advantages of this method include the using of low cost of nickel catalyst, and its simple convenient operation. [ABSTRACT FROM AUTHOR]

An unprecedented aryne 1,2,3-trifunctionalization protocol from 2,6-bis(silyl)aryl triflates was developed under transition-metal-free conditions. The reaction of generated 3-silylaryne with both pyridine N-oxide and N-hydroxylamide afforded o-silyl triflate/tosylate in a one-pot transformation, allowing the formation of 2,3-aryne precursors with various vicinal pyridinyl/amido substituents. These pyridinyl-substituted 2,3-aryne intermediates exhibit a broad scope of reactivity with diverse arynophiles in good yields and high selectivity. [ABSTRACT FROM AUTHOR]

The data on the kinetics of the reaction between hexachlorocyclotriphosphazatriene (the phosphazene) with pyridine N-oxide in mixed organic solvents in the presence of water are presented. The reaction of the phosphazene with pyridine N-oxide leads to the formation of the onium salt. It has been found that water catalyzes this reaction, the catalytic action resulting from the solvation of the polar transition state due to the formation of the phosphazene complex with hydrogen bonding, thus facilitating the rupture of the phosphorus bond with the leaving anion. [ABSTRACT FROM AUTHOR]

Abstract: Cu2O/2,6-bis(2-methylhydrazine-1-carbonyl)pyridine 1-oxide was found to be an efficiently catalytic system for the N-arylation of imidazole, indole, benzimidazole, pyrrole, benzylamine and ethanolamine with aryl iodides and bromides by using NaOH as base in the presence of 20 mol% (n-Bu)4NBr, and water as solvent at 130 °C in 24 h, and giving the N-arylated products in moderate to excellent yields.Graphical Abstract: [ABSTRACT FROM AUTHOR]

The title compound, [HgI2(C10H8N2O2S2)]n, a one-dimensional coordination polymer with HgI2 units and 2,2′-di­thio­bis­(pyridine N-oxide) spacer ligands in an alternating fashion, forms helical chains running along the b axis in the crystal. Within a single coordination polymer strand, the axially chiral 2,2′-di­thio­bis­(pyridine N-oxide) ligands are homochiral, but the enanti­omeric conformation is present in adjacent strands. Within a coordination polymer strand, the iodido ligands point towards the centroids of the aromatic rings of the pyridine N-oxide moieties in the coordination sphere of HgII. Moreover, intra-strand C—HO and C—HI inter­actions, and inter-strand short SI and SO contacts are observed. [ABSTRACT FROM AUTHOR]

The title compound 2,2'-bipyridin-10-ium 1-oxide bromide crystallizes as a monohydrate, C10H9N2+·Br-·H2O. Structural disorder is observed due to the fact that protonation, as well as oxidation, of the N atoms of 2,2'-bipyridine occurs at either of the N atoms. The disorder extends to the remainder of the cation, with a refined occupancy rate of 0.717 (4) for the major moiety. An intramolecular N--H...O hydrogen bond forces the bipyridine unit into an s-cis conformation. Each pair of neighbouring 2,2'-bipyridin-1'-ium ions forms a dimeric aggregate by hydrogen bonds between their respective N--O and the N--H functions. These dimers and hydrogen-bonding interactions with bromide ions and the water molecule give rise to a complex supramolecular arrangement. [ABSTRACT FROM AUTHOR]

Dirhodium(II) catalyzed dinitrogen extrusion from diazocarbonyl compounds by 2,6-dichloropyridine-N-oxide forms ketocarbonyl compounds in near-quantitative yields. Reactions occur at room temperature, and the pyridine product does not coordinate with dirhodium(II) to inhibit catalysis. Anhydrous tricarbonyl compounds, as well as dicarbonyl compounds, are conveniently prepared by this methodology, and they have been used in situ for catalytic ene and aldol transformations. [ABSTRACT FROM AUTHOR]

The evolution mechanism of coal carbon skeleton to polycyclic aromatic hydrocarbons (PAHs) with temperature has been researched by in-situ Raman and solid-state 13C NMR. A theoretical exploration with density functional theory at M06-2X/6-31G(d,p)//def-TZVP level was performed, in order to investigate the mutual conversion pathways among different functional nitrogen, and the relationships between their evolution to NOx precursors and PAHs. The aromatic nucleus radicals produced by homolysis reaction of aliphatic side chains can be connected by carbon-carbon single bonds to form PAHs remaining in char at medium pyrolysis temperature. The participation of olefin compounds cracked from aliphatic side chains is favorable to the conversion of pyrrolic and pyridinic (N-6) nitrogen to NOx precursors and PAHs, and the cyclopentadiene and butadiene obtained by the cleavage of different functional nitrogen in coal skeleton are important intermediates for the formation of PAHs. The conversion of pyridine oxide and quaternary nitrogen (N-Q) to N-6 around 440 °C can compensate for the own thermal decomposition of N-6, while the conversion of N-Q to N-6 is gradually dominated by the reverse reaction from around 690 °C. [ABSTRACT FROM AUTHOR]

A chiral mononuclear Dy III complex, formulated [Dy(PNO) 6 (H 2 O) 2 ]Cl 3 ( 1 ) (PNO = pyridine- N -oxide), has been prepared by using an achiral ligand through spontaneous resolution. Structure analyses show that complex 1 consists of a Dy III mononuclear unit and such units interact with each other by hydrogen bonds to form helical chains along a axis. The crystals of 1 are optically active and opposite Cotton effects can be observed in the circular dichroism (CD) spectra. Magnetic studies reveal that complex 1 exhibits field-induced single molecule magnet behavior with an energy barrier of 49 K. [ABSTRACT FROM AUTHOR]

Three manganese(II) N-oxide complexes have been synthesized from the reaction of manganese(II) chloride with either pyridine N-oxide (PNO), 2-methylpyridine N-oxide (2MePNO) or 3-methylpyridine N-oxide (3MePNO). The compounds were synthesized from methanolic solutions of MnCl2⋅4H2O and the respective N-oxide, and subsequently characterized structurally by single-crystal X-ray diffraction. The compounds are catena-poly[[aquachlorido-manganese(II)]-di-μ-chlorido-[aquachloridomanganese(II)]-bis(μ-pyridine N-oxide)], [MnCl2(C5H5NO)(H2O)]n or [MnCl2(PNO)(H2O)]n (I), catena-poly[[aquachloridomanganese(II)]-di-μ-chlorido-[aquachloridomanganese(II)]-bis(μ-2-methylpyridine N-oxide)], [MnCl2(C6H7NO)(H2O)]n or [MnCl2(2MePNO)(H2O)]n (II), and bis(μ-3-methylpyridine N-oxide)bis[diaquadichloridomanganese(II)], [Mn2Cl4(C6H7NO)2(H2O)4] or [MnCl2(3MePNO)(H2O)2]2 (III). The MnII atoms are found in pseudo-octahedral environments for each of the three complexes. Compound I forms a coordination polymer with alternating pairs of bridging N-oxide and chloride ligands. The coordination environment is defined by two PNO bridging O atoms, two chloride bridging atoms, a terminal chloride, and a terminal water. Compound II also forms a coordination polymer with a similar metal cation; however, the coordination polymer is bridged between MnII atoms by both a single chloride and 2MePNO. The distorted octahedrally coordinated metal cation is defined by two bridging 2MePNO trans to each other, two chlorides, also trans to one another in the equatorial (polymeric) plane, and a terminal chloride and terminal water. Finally, complex III forms a dimer with two bridging 3MePNOs, two terminal chlorides and two terminal waters forming the six-coordinate metal environment. All three compounds exhibit hydrogen bonding between the coordinating water(s) and terminal chlorides. [ABSTRACT FROM AUTHOR]

Two ferrocene-dipeptide conjugates, Fc( l-Ala− l-Pro−PyO)2 ( 2) and Fc( l-Ala− l-Pro−PyO)1 ( 3), were synthesized by the introduction of an l-Ala− l-Pro dipeptide that contained a C-terminal pyridine N-oxide moiety into the ferrocene organometallic scaffold. Single-crystal X-ray structure determination of ferrocene-dipeptide conjugate 2, which was composed of two dipeptide chains, confirmed the formation of intramolecular antiparallel β-sheet-like hydrogen bonds between the CO (Ala) and NH (Ala of another chain) groups to induce a chirality-organized structure in which the ferrocenoyl moiety adopted a P-helical chirality. In the crystal packing of compound 2, the peptide chains adopted a right-handed molecular arrangement through hydrogen-bonding interactions. On the contrary, ferrocene-dipeptide conjugate 3, which was composed of only one dipeptide chain, self-assembled into a tetramer structure through the formation of intermolecular hydrogen bonds and π-π interactions between pyridine N-oxide moieties. [ABSTRACT FROM AUTHOR]

The oxorhenium(V) dimer {MeReO(pdt)} 2 (where pdt = 1,2-propanedithiolate) catalyze the oxygen atom transfer (OAT) reaction from the pyridine oxide to triphenylarsine (Ph 3 As). The rate law is given by ν = k[Re-dimer][PyNO] and zero order dependence on Ph 3 As. The value of k at 25 °C in CHCl 3 is 139 ± 3 L mol −1 s −1 . The activation parameters are ΔH ‡ = 12.2 ± 1.0 kcal mol −1 and ΔS ‡ = −7.9 ± 3.24 cal K −1 mol −1 . According to the proposed mechanism, the rate determining step is the oxidation of Re V O to Re VII O 2 and the pyridine release. The triphenylarsine enters the catalytic cycle after the rate determining step. The reaction constant ρ = −1.4 obtained from Hammett correlation with σ for different substituted pyridine N -oxide. The computational study indicates that the oxidation of Re V to Re VII and release of the pyridine step is insensitive to the nature of the substituent on the pyridine with the average estimated activation barrier ≈11.5 kcal/mol from six different substituted pyridine oxide. It is proposed that electron donor substituent enrich the equilibrium of the first step of the proposed mechanism which is the coordination of the pyridine oxide with one rhenium atom to form I 1 (Scheme 2). The electron donor substituent on the pyridine increase the concentration of I 1 which will increase the rate of the reaction as the ν = k 2 [I 1 ]. [ABSTRACT FROM AUTHOR]

Pharyngitis presents as an inflammation of the oropharynx, and clinical examination often shows evidence of nasopharyngitis. In numerous cases the condition occurs as a self-limiting illness of non-infectious aetiology, whose clinical management remains a matter for debate given the inappropriateness of antibiotics, the reported worsening following steroid use and the recent discouragement of the use of Chinese herbal medicine. The aim of the present study was thus to test VBC-1814/7J, a poly-phytocompound with known anti-inflammatory and immune-response enhancing properties, in an experimental model of non-infectious pharyngitis. Experimental non-infectious pharyngitis was induced by applying a pyridine solution to the surface of the pharyngeal mucosa in rats that were either normally fed (group A) or fed VBC-1814/7J three days prior to and three days subsequent to the induction of pharyngitis (group B). Healthy rats treated with topical saline were used as a control (group C). At time-points of 0, one hour, one day and three days sacrifices were carried out and microscopic examination, Evans blue (EB) dye extravasation and tissue concentrations of tumour necrosis factor (TNF)-a, interleukin (IL)-6 and mRNA of a- and ß-defensins were studied. As compared with group C, group A showed significant microscopic damage, EB extravasation, and increases in the levels of TNF-a and IL-6, as well as in the mRNA of three defensins (P<0.001) on the third day of observation. VBC-1814/7J significantly mitigated these microscopic and inflammatory markers while allowing a prompter and wider defensin reaction (P<0.05 vs. group A). These data suggest that VBC-1814/7J, as demonstrated in earlier studies, has the potential to address non-infectious pharyngitis in clinical practice. [ABSTRACT FROM AUTHOR]

A novel ternary rGO/PPy/S nanocomposite possessing of a hierarchical nanostructure via incorporating the matrix of reduced graphene oxide (rGO) coated by polypyrrole (PPy) with sulphur was prepared by a facile one-pot in situ method. The chemical bonds exist between PPy and rGO through the formation of graphitic N and pyridine oxide N, and the C S, S C = S and S O chemical bonds form between rGO/PPy and S in the structure of the rGO/PPy/S material. The loading content of sulphur is 69.43 wt.% for the rGO/PPy/S sample. The rGO/PPy/S material exhibits a high performance when used as the cathode of Li-S battery. The initial and last discharge capacity arrived at 991.5 and 626.7 mAh g −1 at 1C with 400 cycles which is corresponding to the capacity retention ratio of 63.2%, indicating its very high cyclic stability. The discharge capacity of 537.4 mAh g −1 could be obtained at 5C and it maintained at 442.1 mAh g −1 after 400 cycles with the Coulombic efficiency of more than 90%, showing its excellent rate stability. [ABSTRACT FROM AUTHOR]

A Pd(II)-catalyzed activation and arylation of C(sp2)–H bond directed by pyridine N-oxide in water is achieved with high regioselectivity to form monoarylated products in yields up to 91%. The wide substrate scope highlights the flexibility of the catalyst. The reaction mechanism was proposed and the application of this method was taken as an example by the synthesis of COX-2 inhibitor analog. [ABSTRACT FROM AUTHOR]

The keteniminium ions generated from the protonation of ynamides formed reversible adducts with counter anions and pyridine-N-oxides as well as halogenated solvents. Above 80 °C, the halonium ions selectively undergo a rate-limiting attack by pyridine-N-oxides, leading to (E)-haloenamides in good yields. [ABSTRACT FROM AUTHOR]

The trans and cis form of 4-(4-methoxystyryl)pyridine N-oxide were studied. The spectral characteristics of cis-4-(4-methoxystyryl)pyridine N-oxide were determined in acetonitrile. The melting and thermal decomposition processes of the trans and cisforms of 4-(4-methoxystyryl)pyridine N-oxide were studied by thermochemical methods. It was establish that the thermal decomposition of 4-(4-methoxystyryl)pyridine N-oxide begins with the cleavage of the bond between the pyridine and benzene rings. [ABSTRACT FROM AUTHOR]

Group 12 halides and 2,2′-dithiobis(pyridine N-oxide) (dtpo) form the crystalline the 1D coordination polymers [Zn X2(μ-dtpo-κ2 O: O′)] n [ X = Cl ( 1), Br ( 2), I ( 3)], [Cd3(μ-Cl)4Cl2(μ-dtpo-κ2 O: O′)2(CH3OH)2] n ( 4), [(CdBr2)2(μ3-dtpo-κ3 O, O: O′)2(H2O)2] n ( 5), and [(CdI2)2(μ-dtpo-κ2 O: O′)3] n ( 6) in methanol. The compounds were structurally characterized by single-crystal X-ray analysis. Compounds 1- 3 represent an isomorphous series of single-stranded coordination polymers, whereas the CdII derivatives are structurally diverse. The metal nodes in 4 and 5 are trinuclear and dinuclear cadmium clusters, respectively. In 4 and 5, the metal nodes are linked into double-stranded 1D coordination polymers by two dtpo bridging ligands. Compound 6 contains mononuclear CdI2 units as nodes and can be viewed as an alternating copolymer of CdI2(μ-dtpo-κ2 O: O′)2 and CdI2(μ-dtpo-κ2 O: O′) entities. Owing to the disulfide moiety, the dtpo bridging ligand inevitably exhibits an axially chiral angular structure. The dtpo ligand adopts various coordination modes through the pyridine N-oxide oxygen atoms. [ABSTRACT FROM AUTHOR]

A novel 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX)/pyridine-N-oxide (PNO) cocrystal at 1:1 molar ratio was synthesized by a solvent evaporation method, and its crystal structure was determined using X-ray diffraction (XRD). It crystallizes in the orthorhombic system with thePbcn space group and cell parametersa = 12.712(3)Å,b = 9.315(3)Å,c = 12.909(3)Å. In addition, detonation performance of this cocrystal was estimated. The predicted detonation velocity and detonation pressure of this cocrystal are 7.47 km/s and 23.20 GPa, respectively, suggesting that it is less powerful than β-HMX. Finally, density functional theory, involving binding energy, atoms in molecule (AIM) theory, natural bond orbital (NBO) analysis, band structure, and density of states, was adopted to characterize the driving forces for the formation of this cocrystal. The results show that driving forces are dominated by the interactions between O atoms of PNO and methylene groups of HMX. It is expected that this research provides some bases for further HMX cocrystal design and preparation. [ABSTRACT FROM PUBLISHER]

Regio- and stereoselective addition of alkyl Grignard reagents to pyridine-N-oxides gave C2-alkylated N-hydroxy-1,2,5,6-tetrahydropyridines and trans-2,3-disubstituted N-hydroxy-1,2,5,6-tetrahydropyridines in good to excellent yields. These intermediates were aromatized or alternatively reduced in one-pot methodologies for efficient syntheses of alkylpyridines or piperidines, respectively. These reactions have a broad substrate scope and short reaction times. [ABSTRACT FROM AUTHOR]

The title compound, C5H4ClNOSe, is the product of the reaction of sulfuryl chloride and 2-selanyl-1-pyridine 1-oxide in dichloromethane. The molecule has an almost planar geometry (r.m.s. deviation = 0.012 Å), and its molecular structure is stabilized by an intramolecular secondary Se⋯O interaction of 2.353 (3) Å, closing a four-membered N--C--Se⋯O ring. The title compound represents the first monomeric organoselenenyl chloride stabilized intramolecularly by an interaction of this type. The non-valent attractive Se⋯O interaction results in a substantial distortion of the geometry of the ipso-carbon atom. The endo-cyclic N--C--Se [102.1 (3)°] and exo-cyclic C--C--Se [136.9 (3)°] bond angles deviate significantly from the ideal value of 120° for an sp²-hybridized carbon atom, the former bond angle being much smaller than the latter. In the crystal, molecules are linked by C--H⋯O hydrogen bonds, forming zigzag chains propagating along [010]. The chains, which stack along the a-axis direction, are linked by offset π-π interactions [intercentroid distance = 3.960 (3) Å], forming corrugated sheets parallel to the ab plane. [ABSTRACT FROM AUTHOR]

ABSTRACT The reduction of tris(pyridine-2-carboxylato)manganese(III) by dithionite has been investigated within the temperature window 288-303 K and at pH range 5.22-6.10 in sodium picolinate-picolinic acid buffer medium. The reaction obeys the following stoichiometry: [ABSTRACT FROM AUTHOR]

Atropisomeric biaryl pyridine and isoquinoline N-oxides were synthesized enantioselectively by dynamic kinetic resolution (DKR) of rapidly racemizing precursors exhibiting free bond rotation. The DKR was achieved by ketoreductase (KRED) catalyzed reduction of an aldehyde to form a configurationally stable atropisomeric alcohol, with the substantial increase in rotational barrier arising from the loss of a bonding interaction between the N-oxide and the aldehyde. Use of different KREDs allowed either the M or P enantiomer to be synthesized in excellent enantiopurity. The enantioenriched biaryl N-oxide compounds catalyze the asymmetric allylation of benzaldehyde derivatives with allyltrichlorosilane. [ABSTRACT FROM AUTHOR]

Reported herein is an unprecedented base-promoted deborylative alkylation of pyridine N-oxides using 1,1-diborylalkanes as alkyl sources. The reaction proceeds efficiently for a wide range of pyridine N-oxides and 1,1-diborylalkanes with excellent regioselectivity. The utility of the developed method is demonstrated by the sequential C−H arylation and methylation of pyridine N-oxides. The reaction also can be applied for the direct introduction of a methyl group to 9-O-methylquinine N-oxide, thus it can serve as a powerful method for late-stage functionalization. [ABSTRACT FROM AUTHOR]

The synthesis and structural characterization of six new d 10 Cd(II) and Zn(II) thiocyanato complexes with pyridine- N -oxide compounds: the polymeric catena -[Cd(μ 2 -2-picoline- N -oxide)(μ N,S -NCS) 2 ] ( 1 ), catena -[Cd(μ 2 -3-picoline- N -oxide)(μ N,S -NCS) 2 ] ( 2 ), catena -[Cd(4-nitropyridine- N -oxide) 2 (μ N,S -NCS) 2 ] ( 3 ), the dinuclear [Cd(4-cyanopyridine- N -oxide) 2 (μ N,S -NCS)(NCS)(H 2 O)] 2 ( 4 ) and the mononuclear complexes [Zn(2-picoline- N -oxide) 2 (NCS) 2 (H 2 O)] ( 5 ) and [Zn(4-cyanopyridine- N -oxide) 2 (NCS) 2 (H 2 O)] ( 6 ) are reported. Single crystal X-ray crystallography revealed the 2D polymeric nature in complexes 1 and 2 , the 1D chain in 3 and the dimeric structure in complex 4 with the doubly-bridged Cd(μ N,S -NCS) 2 Cd moiety. Five-coordinate monomeric Zn(II) complexes were obtained in 5 and 6 , where the thiocyanto ligands are acting as monodentate N-bonded. The emission spectral properties of the six complexes were investigated. Very strong enhancing fluorescence intensity was observed in complex 3 . [ABSTRACT FROM AUTHOR]

The 1,1-ADEQUATE spectrum clearly shows specific two-bond proton to carbon correlations to unequivocally distinguish the major and minor regioisomers of ortho-halogenated pyridines and to aid in assignment of the corresponding proton and carbon chemical shifts. M06-2X/6-31+G(d,p) free energies of the regioisomeric intermediates arising from deprotonation correctly predict the experimentally observed preference and thus can be used to tune the substituent pattern to yield a desired regiochemical outcome. [ABSTRACT FROM AUTHOR]

3- and 4-(α-diazophenyl)pyridine-N-oxides, 3- and 4-D1pyO, were prepared as new photoresponsive magnetic couplers in heterospin systems. Lanthanide dinuclear complexes, [LnIII(tta)3(4-D1pyO)]2; LnIII = Gd (1d), Tb (2d), and Dy (3d) and tta = 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionate, bridged with 4-D1pyO in μ2 coordination mode were obtained. The obtained 1d, 2d, and 3d were isostructures. The isomeric complex, [TbIII(tta)3(3-D1pyO)]2 was also prepared. In the carbene-LnIII complexes [LnIII(tta)3(4- and 3-C1pyO)]2 generated by photolysis, C1pyO regioselectively interacted with the LnIII ions through pyridine-N-oxide, in which the magnetic coupling of 4-C1pyO was weakly ferromagnetic, while that of 3-C1pyO was insignificant. Before and after irradiation of 1d, no SMM behavior was observed. In contrast, the TbIII and DyIII complexes being anisotropic functioned as heterospin SMMs. Before irradiation, 2d showed no SMM behavior. After irradiation, two species showing slow magnetic relaxations were produced and one of them exhibited SMM behavior with the thermal activation barrier, Ueff/kB = 30 K, and τ0 = 5.8 × 10−8 s. In 3d, SMM behaviors were observed before and after irradiation, and the Ueff/kB value of 102 K (τ0 = 3.6 × 10−7 s) before irradiation was reduced to 39 K (τ0 = 1.5 × 10−8 s) after irradiation. [ABSTRACT FROM AUTHOR]

The synthesis and structural characterization of two new polymeric zinc(II) azido complexes with pyridine- N -oxide derivative co-ligands, namely catena- [Zn(4-methylpyridine- N -oxide)(μ 1,1 –N 3 ) 2 ] ( 1 ) and catena- {[Zn 2 (μ 2 -isonicotinato- N -oxide) 2 (μ 1,1 –N 3 ) 2 (H 2 O) 3 ](H 2 O)} ( 2 ) are reported. Single crystal structure determination revealed the penta-coordinated geometry of the Zn(II) centers in the polymeric chains of 1 with di-EO azido bridging mode, whereas five and six coordination modes around Zn(II) centers are observed in complex 2 , and the 1D system is formed via alternating single EO-azide and μ(O,O′)-bridging carboxylate group of the isonicotinato- N -oxide molecules. The solid state luminescence properties of 1 were examined. [ABSTRACT FROM AUTHOR]

The heteroaryl ether is an important structural feature in molecules of biological interest, yet it remains a challenge to synthesize. A new and practical method for the synthesis of heteroaryl ethers is reported. In the presence of PyBroP, a variety of nonaromatic alcohols readily add to azine N-oxides to afford the corresponding heteroaryl ethers. The reaction conditions are mild, economical, chemoselective, and compatible with a broad range of substrates. Thirty-eight examples are provided, as is a discussion of reaction optimization and mechanism. [ABSTRACT FROM AUTHOR]

Cethyl-2-Methylresorcinarene forms host–guest complexes with aromatic N-oxides through multiple intra- and intermolecular hydrogen bonds and C–H…π interactions. The host shows conformational flexibility to accommodate 3-methylpyridine N-oxide, while retaining a crown conformation for 2-methyl- and 4-methoxypyridine N-oxides highlighting the substituent effect of the guest. N-Methylmorpholine N-oxide, a 6-membered ring aliphatic N-oxide with a methyl at the N-oxide nitrogen, is bound by the equatorial −N–CH3 group located deep in the cavity. 2-Iodopyridine N-oxide is the only guest that manifests intermolecular N–O…I–C halogen bond interactions, which are broken down by the host resulting in a 2 : 2 pseudocapsular complex stabilized by additional C–I…π interactions between the two 2-iodopyridine N-oxides located in two adjacent hosts. These host–guest complexes were analyzed in the solid state by single crystal X-ray crystallography and in solution by 1H NMR spectroscopy. [ABSTRACT FROM AUTHOR]

Highly chemo- and regioselective synthesis of 2-alkylpyridine N -oxides from pyridine N -oxides and cyclic ethers has been developed through copper-catalyzed CDC reactions using CuO as the catalyst under mild reaction conditions. Optimization study showed that, K 2 S 2 O 8 is the best oxidant for the reaction and the mechanistic study proved the radical pathway for this transformation. It was found that the substrates with electron donating or electron withdrawing groups could react smoothly to afford the desired products. [ABSTRACT FROM AUTHOR]

Quantum chemical calculations using DFT (B3LYP and PBE0) and MP2 approximations with cc-pVTZ basis sets have been performed for 10 N-oxides with different substituents. The influence of the substituent nature on the geometry and redox properties of the compound, as well as on the parameters of the semipolar N → O bond, has been analyzed. The presence of strong electron-withdrawing substituents on the pyridine ring results in increase in the electron affinity value and, consequently, in the enhancement of the antifungal activity of the compound. The compounds with the electron-donating substituents have greater complexation ability. The main conclusions based on the calculation results are in good agreement with the available experimental data. [ABSTRACT FROM AUTHOR]