Pyridine N-oxide Research Articles

A New Class of Redox Isomerization of N-Alkylpropargylamines into N-Alkylideneallylamines Catalyzed by a ReBr(CO)5/Amine N-oxide System.

Redox isomerization reaction wherein N-alkylpropargylamines are converted into N-alkylideneallylamines in the presence of rhenium(I) complexes as catalysts is described. Among the additives tested, certain pyridine N-oxides and tertiary amine N-oxides were effective for the reaction to proceed, and in particular, the use of 2,6-lutidine N-oxides gave the best results. The choice of a diphenylmethyl group as a substituent on the nitrogen atom was key to the success of the reaction, allowing it to reach completion.

Differences in susceptibility of marine bacterial communities to metal pyrithiones, their degradation compounds and organotin antifouling biocides

AbstractThe susceptibility of marine bacterial communities to copper pyrithione (CuPT2), zinc pyrithione (ZnPT2) and their degradation product is described and toxicities of these relatively new antifouling biocides compared with those of their harmful organotin (OT) predecessors, tributyltin (TBT) and triphenyltin (TPT). These biocides were added to agar at concentrations of 0, 0.01, 0.1, 1 and 10 mg l−1and coastal seawater including indigenous bacteria added to each batch of agar solution. The number of bacterial colony forming units (CFU) was measured after 7 days culture. Relative CFU (as a percentage of control) was more than 80% at a concentration of 0.01 mg l−1of each compound, except for TBT. Relative CFU decreased as a function of dose of each biocide, although concentration-dependent changes in rate of CFU were relatively low during exposure to degradation products of CuPT2and ZnPT2, pyridineN-oxide (PO) and pyridine-2-sulphonic acid (PSA). Based on comparisons of EC50, TBT was the most bacterio-toxic of the tested compounds (0.2 mg l−1), marginally more so than CuPT2(0.3 mg l−1). Interestingly, EC50values of degradation products of CuPT2and ZnPT2, 2-mercaptopyridineN-oxide (HPT) and 2,2′-dithio-bispyridineN-oxide (PT2) were 0.8 and 0.5 mg l−1, respectively, lower than that of the parent chemical, ZnPT2(1.4 mg l−1). The EC50of PT2was also lower than that of TPT (0.7 mg l−1), implying higher toxicity. Given the overlapping toxicity ranges, these results suggest that marine bacterial communities experience comparably high susceptibility to metal PTs and OTs during their life history.

Effect of chemical structure of lignite and high-volatile bituminous coal on the generation of biogenic coalbed methane

Biogenic coalbed methane has been attracted much attention due to massive reserves and green performance, but the current research is relatively weak. To further investigate its formation mechanism, the experimental simulation of biogas generation was performed by using lignite, high-volatile bituminous coals and their treated coals as substrates for 90 days. The results show that the lignite has a greater biogas potential than high-volatile bituminous coal in this study. Total gas production in lignite groups (L-BZ-1 and L-LJ-1) is 12.6% more than the bituminous coal groups in the experimental simulation. This is because the lignite has a low degree of thermal evolution and rich in soluble organic matter: chloroform asphalt “A” (CAA), which plays an important role in microbial metabolism to produce biogas. The CAA in coal has a conversion rate of 3.08 mL/g into biogas in this experimental simulation. The saturated hydrocarbons and nonhydrocarbons are more biodegradable components in the CAA. In saturated hydrocarbons, the n-alkanes with shorter chains or an odd carbon number are preferentially degraded. In the experimental simulation, biogas generation results in the consumption of a large number of organic matters with heteroatomic groups such as hydroxyl, carboxyl, pyridine and nitrogen oxides. Aliphatics show a stronger bioactivity than aromatics. The aromatic structure in coal is a few biodegraded in the later stage.

Supercritical Water Oxidation of Pyridine and 3-Cyanopyridine: TOC Removal, Kinetics, and Degradation Pathway

AbstractSupercritical water oxidation (SCWO) has emerged as a promising technique to eliminate refractory aromatic compounds, which are difficult to remove by conventional wastewater-treatment proc...

Experimental and kinetic study on the low-temperature oxidation of pyridine as a representative of fuel-N compounds

The low-temperature oxidation (LTO) of pyridine was studied in a jet-stirred reactor over the temperature range of 700–1000 K at atmospheric pressure and equivalence ratio of 2.0. Mole fraction profiles of the reaction products were obtained based on molecular beam mass spectrometry and tunable vacuum ultraviolet synchrotron photoionization techniques. Hydrogen peroxide, methanamine, acetylenamine, ethenamine, acetaldimine, ethylamine, allyamine, and methylformamide were newly identified compared with previous studies of pyridine flame and pyrolysis. HCN was found to be the dominant N-containing species of pyridine LTO. Pyrrole, acrylonitrile, acetonitrile, and ammonia were also found at the same level of N2O and NO. Based on the new measurements and updated rate constants of several reactions including the H-abstractions of pyridine as well as the oxidation of ortho-pyridyl using density functional theory calculations, a new pyridine LTO kinetic model consisting of 588 species and 3516 reactions was developed with a reasonable agreement with the experimental results. In general, the predictions of the predominant species have been improved compared with the existing model. Rate-of-production analysis indicates that pyridine mainly consumes via C5H5N→C5H4N→C5H4NO2→HCN+CO+CH2CHC˙O, and C5H5N→C5H5NO→C2H2+HCN+CH2CO. Sensitivity analysis shows that C5H4N+O2=>C5H4NO2, and C5H5N+OHC5H4N+H2O have significant promoting effect on pyridine consumption, while the reverse of C5H4N+HO2C5H4NO+OH has strong inhibiting effect. The results will enrich the understanding of pyridine low-temperature oxidation mechanism, which can be applied to the fields of coal pre-treatment, staged combustion and mild combustion.

Urea‐2,2‐dihydroperoxypropane as a Novel and High Oxygen Content Alternative to Dihydroperoxypropane in Several Oxidation Reactions

AbstractUrea‐2,2‐dihydroperoxypropane (UDHPP)‐ a white crystalline solid oxidant which is formed when urea is recrystallized from dihydroperoxypropane‐ was applied as the terminal oxidant in several oxidative procedures namely epoxidation of α, β‐unsaturated ketones and alkenes, oxidation of sulfides to sulfoxides and sulfones, bayer‐villeger reaction, bromination and iodation of aniline and phenol derivatives, oxidative esterification, oxidative amidation of aromatic aldehydes, thiocyanation of aromatic compounds, and oxidation of pyridines, oxidation of secondary, allylic and benzylic alcohols. All the approaches were carried out under mild conditions and short reaction times and afforded the corresponding products in high yields.

2-Substituted Benzimidazole Synthesis in Dry Medium Mediated by Pyridine N-oxide

Substituted benzimidazoles were obtained from o-phenylenediamine and organic halides in solvent-free medium. The procedure involves pyridine N-oxide as mild oxidizing agent. The benzimidazoles were prepared without the separation of the intermediates. The absence of catalysts and good yields are important benefits of the method.

Synthetic, structural and reaction chemistry of N-heterocyclic germylene and stannylene compounds featuring N-boryl substituents.

This study details the syntheses of N-heterocyclic germylenes and stannylenes featuring diazaborolyl groups, {(HCDippN)2B} (Dipp = 2,6-iPr2C6H3), as both of the N-bound substituents, with a view to generating electron rich and sterically protected metal centres. The energies of their key frontier orbitals - the group 14-centred lone pair and orthogonal pπ-orbital (typically the HOMO-2 and LUMO) have been probed by DFT calculations and compared with a related acyclic analogue, revealing (in the case of the stannylenes) a correlation with the measured 119Sn chemical shifts. The reactivity of the germylene systems towards oxygen atom transfer agents has been examined, with 2 : 1 reaction stoichiometries being observed for both Me3NO and pyridine N-oxide, leading to the formation of products thought to be derived from the activation of C-H bonds by a transient first-formed germanone.

СИНТЕТИЧНІ ПІРИДИНОВМІСНІ АМІНОКИСЛОТИ ТА ЇХНІ ПОХІДНІ

This paper reports on the synthesis of new derivatives of ε-aminocaproic and γ-aminobutyric acid modified with a pyridin-2-yl substituent at the ω-position of the main chain. The hemostatic activity of both ε-aminocaproic acid itself and its various synthetic analogues is widely known. Likewise, numerous γ-aminobutyric acid derivatives are strong neurotransmitters extensively used in the treatment of the nervous system disorders. No less popular are biologically active substances containing a pyridine or piperidine fragment; among which there are antibiotics, antimalarial, anti-sclerotic and antiallergic drugs, as well as anti-depressants and analgesics. Therefore, the introduction of the pyridine fragment into the amino acid structures is interesting in terms of their potential biological activity investigation. So, a method for the synthesis of 5-amino-5-(pyridin-2-yl)pentanoic and 6-amino-6-(pyridin-2-yl)hexanoic acid has been developed by us. The proposed scheme is based on the available reagents using. The key stage is the Schmidt rearrangement of 2-(pyridin-2-yl)cyclopentanone and 2-(pyridin-2-yl)cyclohexanone, previously synthesized from pyridine N-oxide and cycloalkenyl morpholinide. For synthesized pyridine substituted cycloalkanones according to NMR spectroscopy, the presence of keto-enol tautomerism was established. As a result of Schmidt rearrangement, lactams (2-(pyridin-2-yl)piperidone and 2-(pyridin-2-yl)azepanone) are formed, and the last ones had been hydrolyzed in an acidic medium to open the lactam cycle. Thus, 5-amino-5-(pyridin-2-yl)pentanoic and 6-amino-6-(pyridin-2-yl)hexanoic acid were isolated as hydrochlorides and the hydrochlorides were converted to the zwitterion form using propylene oxide. The first stage of the developed scheme (preparation of pyridylalkanones) occurs in rather low yields, about 35 %. But, after the rearrangement, hydrolysis and the formation of zwitterion do not cause difficulties and are characterized by high yields. Consequently, the proposed synthetic sequence is preparatively advantageous.

Metal- and base-free regioselective thiolation of the methyl C(sp3)–H bond in 2-picoline N-oxides

Metal- and base-free thiolation of the unactivated methyl C(sp3)–H bond in 2-picoline N-oxides with thiols is achieved by a one-pot, two-step sequence, including a TFAA-mediated [3,3]-sigmatropic rearrangement of pyridine N-oxides and TBAB-catalyzed direct conversion of trifluoroacetates into thioethers.

Regioselective conversions of H4pdta (1,2-propanediaminetetraacetic acid) and H4eed3a to their triacetates on peroxotitanates.

1,2-Propanediaminetetraacetic acid (H4pdta = C11H18O8N2) is degraded selectively to 1-methyl-1,2-propanediaminetriacetic acid (H3pd3a = C9H16O6N2) with a yield of 75% at room temperature, while N-(2-hydroxyethyl) ethylenediaminetriacetic acid (H4eed3a = C10H18O7N2) is converted with difficulty to ethylenediaminetriacetic acid (H3ed3a = C8H14O6N2) on peroxotitanates(iv), showing the influence of the uncoordinated leaving group. Various species in the reaction sequence are isolated and fully characterized, including (NH4)[Ti(O2)(Hpdta)]·H2O (1), (NH4)3[Ti(O2)(pdta)H(pdta)(O2)Ti]·7H2O (2), (NH4)[Ti(O2)(pd3a)]·H2O (3) and (NH4)[Ti(O2)(Heed3a)]·H2O (5). Peroxo dimer 2 forms a strong intramolecular hydrogen bond [2.451(3) Å] as an intermediate in the peroxo Ti-pdta system, which results in the absence of a fully deprotonated species of peroxo pdta titanate. A catalytic reaction of the peroxo titanate (NH4)3[Ti(O2)(pdta)H(pdta)(O2)Ti]·7H2O (2) for the conversion of pyridine to pyridine N-oxide shows 94% conversion at 80 °C.

Synthesis of helical π-conjugated polymers bearing pyridine N-oxide pendants and asymmetric allylation of aldehydes in the helical cavity.

Catalytically active chiral π-conjugated polymers (poly-1(NO)r) bearing pyridine N-oxide pendants were synthesized by ternary copolymerization of a d-glucose-bound diethynyl compound with two types of thieno[3,4-b]thiophene comonomer, one of which contained a pyridine N-oxide group. When the pyridine N-oxide content in the copolymer was 10 mol% (poly-1(NO)0.10), the polymer backbone formed a one-handed helical structure in acetonitrile. Pyridine N-oxide pendants arranged inside the helical cavity of poly-1(NO)0.10 exhibited catalytic activity for the asymmetric allylation of benzaldehydes, producing the corresponding allyl alcohols with up to 43% ee.

The m-CPBA–NH3(g) System: A Safe and Scalable Alternative for the Manufacture of (Substituted) Pyridine and Quinoline N-Oxides

An improved, safe, and scalable isolation process for (substituted) pyridine and quinoline N-oxides in quantitative yields along with high purities using the m-CPBA–NH3(g) system is described. The safety was assessed by reaction calorimetry and differential scanning calorimetry studies for possible hazards during the conversion and isolation steps. Careful interpretation of the data substantiated the safety and scalability. The process flow is simplified to meet the industrial requirements of safety, cost-effectiveness, and utility minimization. The reaction was safely demonstrated at a 2.5 kg scale.

Enantioselective Construction of Pyridine N-Oxides Featuring 2,3-Dihydrofuran Motifs via Phosphine-Catalyzed [4 + 1]-Annulation of 2-Enoylpyridine N-Oxides with Morita-Baylis-Hillman Carbonates.

The first example of phosphine-catalyzed enantioselective [4 + 1] annulations between 2-enoylpyridine N-oxides and Morita-Baylis-Hillman carbonates is described. When 1,2-bis[(2 R,5 R)-2,5-dimethylphospholano]benzene monoxide is employed as organocatalyst, Morita-Baylis-Hillman carbonates react with 2-enoylpyridine N-oxides smoothly to afford a series of optically active 2,3-dihydrofurans in high yields (up to 96%) with excellent stereoselectivities (96 → 99% ee and >20:1 dr). Importantly, the method offers a facile synthetic approach to enantioenriched pyridine N-oxides featuring 2,3-dihydrofuran motifs.

Visible-Light Photocatalyzed Deoxygenation of N-Heterocyclic N-Oxides

A scalable and operationally simple method is described that allows for the chemoselective deoxygenation of a wide range of N-heterocyclic N-oxides (a total of 36 examples). This visible-light-induced protocol features the use of only commercially available reagents, room-temperature conditions, and unprecedented chemoselective removal of the oxygen atom in a quinoline N-oxide in the presence of a pyridine N-oxide in the same molecule through the judicious selection of a photocatalyst.

Collagen functionalized graphene sheets decorated with in situ synthesized nano hydroxyapatite electrospun into fibers

We report the in situ synthesis of hydroxyapatite nanoparticles on 1–3 layers of colloidal collagen-graphene composites. Varying calcium and phosphate: graphene ratio two different composites were synthesized. Crystallite size, particle size and degree of crystallinity of hydroxyapatite nanoparticles changes with a change in graphene concentration. Transmission electron microscopy shows that these graphene composites change shape from spherical to elongated needle-like structures because of the varying nitrogen content in collagen-graphene. Fourier-transform Infrared Spectroscopy peaks suggests an interaction between calcium and the colloidal composites. X-ray Photo Electron spectroscopy data shows the interaction between graphene, collagen and hydroxyapatite through pyridinic N-oxide moiety. High-resolution lattice images confirm the co-existence of both graphene and hydroxyapatite. Anti-bacterial tests of the colloidal composites with two different bacteria S. Marcences and E. Coli show improved anti- bacterial property with increased graphene concentration. The colloidal composites were further electrospun into fibers, and their electrochemical stability in simulated body fluids estimated. The electrochemical test data show that the fiber made of composites would be extremely useful for biomedical applications such as internal bandages and burns.

Metabolism and disposition of pyrotinib in healthy male volunteers: covalent binding with human plasma protein.

Pyrotinib is a novel irreversible EGFR/HER2 dual tyrosine kinase inhibitor that is used to treat HER2-positive breast cancer. In this study we investigated the metabolism and disposition of pyrotinib in six healthy Chinese men after a single oral dose of 402 mg of [14C]pyrotinib. At 240 h postdose, the mean cumulative excretion of the dose radioactivity was 92.6%, including 1.7% in urine and 90.9% in feces. In feces, oxidative metabolites were detected as major drug-related materials and the primary metabolic pathways were O-depicoline (M1), oxidation of pyrrolidine (M5), and oxidation of pyridine (M6-1, M6-2, M6-3, and M6-4). In plasma, the major circulating entities identified were pyrotinib, SHR150980 (M1), SHR151468 (M2), and SHR151136 (M5), accounting for 10.9%, 1.9%, 1.0%, and 3.0%, respectively, of the total plasma radioactivity based on the AUC0-∞ ratios. Approximately 58.3% of the total plasma radioactivity AUC0-∞ was attributed to covalently bound materials. After incubation of human plasma with [14C]pyrotinib at 37 °C for 2, 5, 8, and 24 h, the recovery of radioactivity by extraction was 97.4%, 91.8%, 69.6%, and 46.7%, respectively, revealing covalent binding occurred independently of enzymes. A group of pyrotinib adducts, including pyrotinib-lysine and pyrotinib adducts of the peptides Gly-Lys, Lys-Ala, Gly-Lys-Ala, and Lys-Ala-Ser, was identified after HCl hydrolysis of the incubated plasma. Therefore, the amino acid residue Lys190 of human serum albumin was proposed to covalently bind to pyrotinib via Michael addition. Finally, the covalently bound pyrotinib could dissociate from the human plasma protein and be metabolized by oxidation and excreted via feces.

Cerium-based catalysts for N-oxidation of pyridine-based derivatives: homogeneous and heterogeneous systems

Herein, the catalytic properties of the cerium (IV) salt, cerium (IV)-sandwiched polyoxometalate (POM) and cerium (IV)-sandwiched polyoxometalate intercalated in layered double hydroxides (LDHs) in the H2O2-based green oxidation reactions have been evaluated. These cerium (IV)-based systems were applied as homogeneous and heterogeneous catalysts for the oxidation of pyridines. Despite the fact that the cerium (IV)-sandwiched polyoxometalate as a homogeneous reaction system gives good results, there are some disadvantages in recovery and reusability process. To overcome these problems, new nano catalyst was synthesized by intercalation of the Cerium (IV)-sandwiched polyoxometalate into tris(hydroxymethyl) aminomethane-modified layered double hydroxides (Tris-LDH-CO3). The as-prepared nanocomposite was characterized and used as an effective heterogeneous catalyst for the oxidation of pyridines under mild conditions in the presence of H2O2 as an oxidant. The new heterogeneous nanocomposite can be recovered and reused easily from the reaction media at least ten times without significant decrease in catalytic activity.

Nickel-Catalyzed Decarboxylative Alkylation of Aryl Iodides with Anhydrides

We present the anhydride-based decarboxylative alkylation of aryl iodides catalyzed by nickel. This method of decarboxylative coupling works with a broad scope of aliphatic carboxylic anhydrides and tolerates synthetically useful aromatic substituents. Assisted by a redox system of pyridine N-oxide and zinc additives, the current reaction occurs under mild conditions and without the assistance of photocatalyst. Notably, this method features high chemoselectivity toward alkyl migration with mixed aliphatic/aromatic anhydrides. Thus, it provides a powerful synthetic tool to modify high-valued aliphatic carboxylic acids by converting them into mixed anhydrides using readily available aryl carboxylic acids such as p-toluic acid. We propose a catalytic cycle that involves the key steps of free radical-based decarboxylation and subsequent alkyl transfer to nickel that precedes an oxidatively induced C–C reductive elimination from Ni(III).

Phase Transfer of the Organic Substrate in the Epoxidation Reaction of Allyl Chloride in Two-Phase Aqueous–Organic Systems

The mechanism of synergism for mixtures of phase-transfer carriers QХ with tertiary amines and pyridine in the epoxidation reaction of allyl chloride has been established. It has been shown that tertiary amines (triethylamine, tributylamine, N,N-dimethylaniline, and N-methyldiethanolamine) and pyridine oxidizable in situ to N-oxides promote the transfer of the organic substrate (allyl chloride) to the interface (PB). It is assumed that the synergism of mixtures of phase-transfer carriers QХ with a tertiary amine oxide or pyridine oxide can also be due to the formation of a mixture of two catalysts, Q3[PW4O24] and WO(O2)2L (where L = a tertiary amine oxide or pyridine oxide). The WO(O2)2L complex will provide the stage of reoxidation of the complex Q3[PW4O24 −х] in the organic phase and, hence, the possibility for the development of the process of epoxidation not only at the interface but also in the bulk of the organic phase. The maximum coefficient of synergistic effect (ks = 2) is observed for a mixture of cetylpyridinium bromide (90 mol %) and pyridine N-oxide (10 mol %).