- Visible-Light-Induced ortho-Selective Migration on Pyridyl Ring: Trifluoromethylative Pyridylation of Unactivated Alkenes
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The photocatalyzed ortho-selective migration on a pyridyl ring has been achieved for the site-selective trifluoromethylative pyridylation of unactivated alkenes. The overall process is initiated by the selective addition of a CF3 radical to the alkene to provide a nucleophilic alkyl radical intermediate, which enables an intramolecular endo addition exclusively to the ortho-position of the pyridinium salt. Both secondary and tertiary alkyl radicals are well-suited for addition to the C2-position of pyridinium salts to ultimately provide synthetically valuable C2-fluoroalkyl functionalized pyridines. Moreover, the method was successfully applied to the reaction with P-centered radicals. The utility of this transformation was further demonstrated by the late-stage functionalization of complex bioactive molecules.
- Jeon, Jinwon,He, Yu-Tao,Shin, Sanghoon,Hong, Sungwoo
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- Grafting of a rhenium-oxo complex on Schiff base functionalized graphene oxide: An efficient catalyst for the oxidation of amines
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A rhenium-oxo complex such as methyltrioxorhenium (MTO) has been homogeneously immobilized on a Schiff base modified graphene oxide (GrO) support via covalent bonding. The loading of MTO on GrO nanosheets was monitored by FTIR, TG-DTA, and elemental analyses. The developed heterogeneous catalyst is found to be efficient for the oxidation of various amines to the corresponding N-oxides using hydrogen peroxide as an oxidant in high to excellent yields. At the end of the reaction, the catalyst is readily recovered by filtration and reused for subsequent runs. After the third run, the catalyst showed a marginal decrease in catalytic activity owing to the leaching of the MTO complex from the support. This journal is the Partner Organisations 2014.
- Khatri, Praveen K.,Choudhary, Shivani,Singh, Raghuvir,Jain, Suman L.,Khatri, Om P.
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- A simple and efficient method for the preparation of pyridine-N-oxides II
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Oxidation of pyridines with bis(trimethylsilyl)peroxide in the presence of catalytic amounts of inorganic rhenium derivatives gives high yields of their analytically pure N-oxides by simple work-ups, typically a filtration or a Kugelrohr distillation.
- Coperet, Christophe,Adolfsson, Hans,Chiang, Jay P.,Yudin, Andrei K.,Sharpless, K. Barry
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- Strategic Approach on N-Oxides in Gold Catalysis – A Case Study
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An extensive kinetic study of selected key reactions of (oxidative) gold catalysis concentrates on the decrease of the catalytic activity due to inhibition of the gold(I) catalyst caused by pyridine derivatives that are obtained as by-products if N-oxides are applied as oxygen donors. The choice of the examined pyridine derivatives and their corresponding N-oxides has been made regardless of their commercial availability; particular attention has been paid to the practical benefit which up to now has been neglected in most of the reaction screenings. The test reactions were monitored by GC and 1H NMR spectroscopy. The received reaction constants provide information concerning a correlation between the electronic structure of the heterocycle and the catalytic activity. Based on the collected kinetic data, it was possible to develop a basic set of three N-oxides which have to be taken into account in further oxidative gold(I)-catalyzed reactions. (Figure presented.).
- Schie?l, Jasmin,Stein, Philipp M.,Stirn, Judith,Emler, Kirsten,Rudolph, Matthias,Rominger, Frank,Hashmi, A. Stephen K.
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- Rational design, synthesis, and characterization of deep blue phosphorescent Ir(III) complexes containing (4′-Substituted-2′- pyridyl)-1,2,4-triazole ancillary ligands
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On the basis of the results of frontier orbital considerations, 4-substituted-2′-pyridyltriazoles were designed to serve as ancillary ligands in 2-phenylpyridine main ligand containing heteroleptic iridium(III) complexes that display deep blue phosphorescence emission. The iridium(III) complexes, Ir1-Ir7, prepared using the new ancillary ligands, were found to display structured, highly quantum efficient (Φp = 0.20-0.42) phosphorescence with emission maxima in the blue to deep blue 448-456 nm at room temperature. In accord with predictions based on frontier orbital considerations, the complexes were observed to have emission properties that are dependent on the electronic nature of substituents at the C-4 position of the pyridine moiety of the ancillary ligand. Importantly, placement of an electron-donating methyl group at C-4′ of the pyridine ring of the 5-(pyridine-2′-yl)-3-trifluoromethyl-1,2,4-triazole ancillary ligand leads to an iridium(III) complex that displays a deep blue phosphorescence emission maximum at 448 nm in both the liquid and film states at room temperature. Finally, an OLED device, constructed using an Ir-complex containing the optimized ancillary ligand as the dopant, was found to emit deep blue color with a CIE of 0.15, 0.18, which is close to the perfect goal of 0.15, 0.15.
- Park, Hea Jung,Kim, Ji Na,Yoo, Hyun-Ji,Wee, Kyung-Ryang,Kang, Sang Ook,Cho, Dae Won,Yoon, Ung Chan
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- Synthese regioselective par voie organometallique de pyridines, 4-picolines et 3,5-lutidines substituees en 2 par un groupe insature et/ou fonctionnel
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A regioselective one-pot synthesis of 2-substituted pyridine derivatives from N-alkoxycarboxylpyridinium salts and α-unsaturated organozinc compounds is described.Similarly, functional alkynyl organomagnesium compounds lead to 2-alkynyl-ω-functional pyridines, from which (E)-2-alkenyl or 2-alkyl-ω-functional pyridines can be obtained by partial or complete reduction.
- Al-Arnaout, A.,Courtois, G.,Miginiac, L.
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- Reaction of Pyridine-N-Oxides with Tertiary sp2-N-Nucleophiles: An Efficient Synthesis of Precursors for N-(Pyrid-2-yl)-Substituted N-Heterocyclic Carbenes
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N-(Pyrid-2-yl)-substituted azolium and pyridinium salts, precursors for hybrid NHC-containing ligands, were obtained with excellent regioselectivity, employing a deoxygenative CH-functionalization of pyridine-N-oxides with substituted imidazoles, thiazoles, and pyridine. Unlike the traditional SNAr-based methods, this approach provides high yields for substrates bearing substituents of different electronic nature. The utility of azolium and pyridinium salts thus prepared was also highlighted by the synthesis of pyridyl-substituted imidazolyl-2-thione, benzodiazepine as well as 2-aminopyridines.
- Bugaenko, Dmitry I.,Karchava, Alexander V.,Yurovskaya, Marina A.
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- Ruthenium catalyzed oxidation of tertiary nitrogen compounds with molecular oxygen: An easy access to N-oxides under mild conditions
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A variety of tertiary nitrogen compounds have been efficiently oxidized to their corresponding N-oxides in excellent yields with molecular oxygen as a sole oxidant and ruthenium trichloride as catalyst.
- Jain, Suman L.,Sain, Bir
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- Bromamine-T/RuCl3 as an efficient system for the oxidation of tertiary amines to N-oxides
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A variety of tertiary amines were efficiently and selectively oxidized to the corresponding N-oxides by bromamine-T using ruthenium trichloride as catalyst in alkaline (pH8.4) acetonitrile/water (1:1) at 80°C.
- Sharma, Vishal B.,Jain, Suman L.,Sain, Bir
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- Preparation, characterization, and aquation kinetics of pyridine N-oxide complexes of chromium(III)
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A series of (H2O)5Cr(X-pyO)3+ ions (pyO = pyridine N-oxide, X = H, 3-CH3, 4-CH3, 4-OCH3, 4-NO2) were prepared by the reduction of the corresponding pyridine N-oxide adducts of diperoxochromium(VI) species with acidic ferrous perchlorate. The (H2O)5Cr(X-pyO)3+ complexes undergo aquation to yield Cr(H2O)63+ and X-pyO according to the rate law kobs = ko + k -1[H+]-1. The values of the rate constants extrapolated to 298 K at 1.0 M ionic strength are: k0 = 2.80 × 10-6 s-1, k-1 = 1.86 × 10-8 M s-1 (X = 4-NO2); 7.80 × 10-8, 6.27 × 10-10 (H); 4.80 × 10-8, 3.20 × 10 -10 (3-CH3); 3.05 × 10-8, 1.60 × 10-10 (4-CH3); and 2.37 × 10-9, 4.76 × 10-11 (4-OCH3). The reaction of the 4-OCH 3 complex exhibits two additional terms in the rate law, k 1[H+] + k-2[H+]-2. The binding of 4-OCH3-pyO to chromium is suggested to take place through the methoxy group. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Kotowski, Mirjana,Marcec, Radovan,Butkovic, Vjera,Bakac, Andreja,Orhanovic, Matko
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- The M?CPbA?NH3(G) system: A safe and scalable alternative for the manufacture of (substituted) pyridine and quinoline N?oxides?
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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.
- Palav, Amey,Misal, Balu,Ernolla, Anilkumar,Parab, Vinod,Waske, Prashant,Khandekar, Dileep,Chaudhary, Vinay,Chaturbhuj, Ganesh
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- Equilibrium of acetyl transfer between pyridine N-Oxides and their acetylonium salts
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The equilibrium constants of acetyl transfer between O-acetylonium salts of a series of pyridine N-oxides and 4-(4-dimethylaminostyryl)pyridine N-oxide in acetonitrile and methylene chloride were determined. The equilibrium constants correlate with the ac
- Rybachenko,Chotii,Kovalenko,Schroeder
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- Hydrogen bonding network assembled with 2-amino-3-hydroxypyridium and isonicotinate-N-oxide
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The crystal structure of the compound (C5H7N 2O)?(C6H4NO3)?H 2O (1) consisting of 2-amino-3-hydroxypyridium, isoniconate-N-oxide and lattice water was characterized by single-crystal X-ray diffraction analysis: monoclinic, P21/c, a = 9.6905(8), b = 6.0040(4), c = 21.039(2) A, β = 101.062(8)°, V = 1201.34(18) A3, Z = 4. In 1, the deprotonated isoniconate-N-oxide, the protonated 2-amino-3-hydroxypyridium and the lattice water are linked by a series of classical hydrogen bonds to form 2-D layer. Then, these 2-D sheets assemble to a 3-D network via weak hydrogen bonds.
- Hu, Rui-Xiang,Huang, Ling,Liang, Hong,Yu, Kai-Bei
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- REACTION OF PYRIDINE N-OXIDES WITH TRIFLIC ANHYDRIDE: FORMATION OF N-SULFONYLOXY AND DIPYRIDINIUM ETHER SALTS
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Pyridine and picoline-N-oxides react with (CF3SO2)2O to give N-sulfonyloxy and dipyridinium ether triflate salts.
- Chen, Zhen-Chu,Stang, Peter J.
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- A mild and efficient H2O2 oxygenation of N-heteroaromatic compounds to the amine N-oxides and KI deoxygenation back to the tertiary amine with hexaphenyloxodiphosphonium triflate
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A mild and efficient method for the oxidation of N-heteroaromatic compounds to the corresponding N-oxides using H2O2 in the presence of hexaphenyloxodiphosphnium triflate (Hendrickson reagent) in EtOH at room temperature was reported. This methodology presented relatively fast and selective reactions to afford the N-oxides in good yields. The reverse reactions, deoxygenation reactions, were also carried out under the same reaction conditions by KI to produce the tertiary amines.
- Khodaei, Mohammad Mehdi,Alizadeh, Abdolhamid,Hezarkhani, Hadis Afshar
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- Reactivity of perfluoro-(cis-2,3-dialkyloxaziridines) with heteroaromatic nitrogen compounds
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Pyridine N-oxides 3 are exclusively formed under particularly mild conditions when perfluorinated dialkyloxaziridines 1 are reacted with pyridine derivatives 2 bearing a substituent at the 2-position. Starting from pyridines substituted at the 3- and 4-positions, the previously unreported N-perfluoroacylpyridiniumaminides 4 are also produced and isolated as solid, stable compounds. Bis(pyridinium-N-aminides) 9, which have been prepared starting from bis-pyridine substrates and pyridazine and quinoxaline starting materials, also show the same reactivity. This behaviour reveals how oxaziridines 1 can work as both animating and oxygenating agents.
- Bernardi, Rosanna,Novo, Barbara,Resnati, Giuseppe
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- Catalytic system for pyridine oxidation to N-oxides under mild conditions based on polyoxomolybdate
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A reusable and effective catalytic system has been developed for oxidation of pyridines catalyzed by Keplerate polyoxomolybdate ({Mo132}) at room temperature. Pyridine compounds could be oxidized in high yields under mild conditions.
- Yang, Chunxia,Zhao, Wei,Cheng, Zhiguo,Luo, Baomin,Bi, Dongqin
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- Enthalpies of combustion of the pyridine N-oxide derivatives: 4-methyl-, 3-cyano-, 4-cyano-, 3-hydroxy-, 2-carboxy-, 4-carboxy-, and 3-methyl-4-nitro, and of the pyridine derivatives: 2-carboxy-, and 4-carboxy-. The dissociation enthalpies of the N-O bonds
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The standard (po = 0.1 MPa) molar enthalpies of formation ΔfHom(cr) at T = 298.15 K were determined using static-bomb calorimetry for crystalline 4-methylpyridine N-oxide (4MePyNO), 3-cyanopyridine N-oxide (3CNPyNO), 4-cyanopyridine N-oxide (4CNPyNO), 3-hydroxypyridine N-oxide (3OHPyNO), 2-pyridinecarboxylic acid N-oxide (2CO2HPyNO), 4-pyridinecarboxylic acid N-oxide (4CO2HPyNO), 3-methyl-4-nitropyridine N-oxide (3Me4NO2PyNO), 2-pyridinecarboxylic acid (2CO2HPy), and 4-pyridinecarboxylic acid (4CO2HPy). The standard molar enthalpies of sublimation ΔgcrHom at T = 298.15 K were measured by microcalorimetry, or by a mass-loss effusion technique, and from the enthalpies of formation of the gaseous compounds the dissociation enthalpies Dom of the (N+-O-) dative covalent bonds were derived. ΔfHom(cr)/(kJ · mol-1) ΔgcrHom/(kJ · mol-1) Dom(N-O)/(kJ · mol-1) 4-MePyNO 5.6 ± 2.1 85.3 ± 2.6 262.4 ± 3.4 3-CNPyNO 170.9 ± 1.4 101.9 ± 2.0 254.3 ± 3.1 4-CNPyNO 162.8 ± 1.4 104.4 ± 4.3 265.5 ± 4.6 3-OHPyNO -171.3 ± 1.0 121.8 ± 4.4 255.0 ± 4.8 2-CO2HPyNO -364.1 ± 1.8 94.4 ± 4.0 275.9 ± 5.1 4-CO2HPyNO -381.2 ± 1.3 136.1 ± 1.2 259.5 ± 5.0 3-Me4NO2PyNO -19.5 ± 3.4 106.7 ± 2.0 263.4 ± 7.1 2-CO2HPy -341.0 ± 1.2 98.0 ± 2.3 4-CO2HPy -348.7 ± 1.6 113.9 ± 4.4 Comparison has been made with Dom(N-O) values in pyridine N-oxide derivatives.
- Ribeiro da Silva, Maria D. M. C.,Agostinha,Matos,Vaz, M. Claudia,Santos, Luis M.N.B.F.,Pilcher,Acree Jr.,Powell, Joyce R.
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- Oxidation of tertiary nitrogen compounds to N-oxides by molecular oxygen-aldehyde system in the absence of metal catalyst
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A variety of tertiary nitrogen compounds have been oxidized to corresponding N-oxides in near quantitative yields by molecular oxygen/2-methylpropanal system in the absence of metal catalyst.
- Dongre,Venkateshwar Rao,Sharma,Sain,Bhatia
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- SYNTHESIS OF PYRIDINE N-OXIDE-SbCl5 COMPLEXES AND THEIR INTRAMOLECULAR AND OXYGEN-TRANSFER REACTION
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Mixing with equimolar solutions of pyridine N-oxide or its homologs and SbCl5 in CCl4 deposited 1:1 complexes as colorless crystals in high yield.On thermolysis, these complexes underwent intramolecular oxygen transfer to give selectively the corresponding 2-pyridone derivatives.N,N-Dimethylaniline N-oxide and SbCl5 also gave a crystalline 1:1 complex which on termolysis yield o-dimethylaminophenol in good yield.
- Yamamoto, Jiro,Imagawa, Masahiro,Yamauchi, Sigeyuki,Nakazava, Osamu,Umezu, Masahiro,et al.
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- Facile Immobilization of a Lewis Acid Polyoxometalate onto Layered Double Hydroxides for Highly Efficient N-Oxidation of Pyridine-Based Derivatives and Denitrogenation
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N-Oxides are a class of highly important compounds that are used widely as synthetic intermediates. In this paper, we demonstrate for the first time the use of a polyoxometalate-based composite material as a highly efficient heterogeneous catalyst for the N-oxidation of pyridines and its derivatives in the presence of H2O2 at room temperature. The composite was prepared by the intercalation of the [La(PW11O39)2]11- anion into a layered double hydroxide (LDH) modified with tris(hydroxymethyl)aminomethane (Tris). Additionally, the Tris-LDH-La(PW11)2-based catalyst has been employed for the denitrogenation of a model oil mixture in the presence of 1-butyl-3-methylimidazolium tetrafluoroborate and H2O2. Denitrogenation can be achieved in 40 min at 75 C. Finally, the heterogeneous catalyst can be recovered easily and reused at least 10 times without a measurable decrease of the catalytic activity and disintegration of the Tris-LDH-La(PW11)2 structure. Between the sheets: We demonstrate for the first time the use of a polyoxometalate-based composite material as a highly efficient heterogeneous catalyst for the N-oxidation of pyridines and its derivatives in the presence of H2O2 at room temperature. The composite is prepared by the intercalation of the [La(PW11O39)2]11- anion into a layered double hydroxide modified with tris(hydroxymethyl)aminomethane.
- Liu, Kai,Yao, Zhixiao,Miras, Haralampos N.,Song, Yu-Fei
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- Oxidation of alcohols and pyridines by a water-soluble polyoxometalate with hydrogen peroxide
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A water-soluble catalyst based on a silicotungstate polyoxometalate, K 8[β-SiW11O39] · 14H2O, was developed for the oxidation of pyridines and alcohols with hydrogen peroxide. The reactions were carried out in water, and good yields of the corresponding heterocyclic N-oxides and ketones were obtained under relatively mild conditions. The catalyst could be easily recovered by extraction with ethyl acetate and reused several times. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications to view the free supplemental file.
- Zhang, Zhenxin,Zhu, Qianqian,Ding, Yong
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- Selective oxidation of pyridine to pyridine-N-oxide with hydrogen peroxide over Ti-MWW catalyst
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The oxidation of pyridine to pyridine-N-oxide (PNO) with hydrogen peroxide has been investigated on various titanosilicate catalysts. Superior to other titanosilicates like TS-1, Ti-Beta and Ti-MOR, Ti-MWW showed a higher catalytic activity and product se
- Xie, Wei,Zheng, Yuting,Zhao, Song,Yang, Junxia,Liu, Yueming,Wu, Peng
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- A green catalytic procedure for oxidation of pyridines catalyzed by a lacunary polyoxometalate in water at room temperature
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A green and reusable catalytic procedure for oxidation of pyridines to N-oxides was developed. High yields of heterocyclic N-oxides were obtained when catalyzed by Δ-Na8HPW9O34 in water at room temperature. The catalyst used in the system could be recovered and reused several times without obvious loss of activity.
- Zhao, Wei,Yang, Chunxia
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- The oxidation of pyridine and alcohol using the Keggin-type lacunary polytungstophosphate as a temperature-controlled phase transfer catalyst
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A novel temperature-controlled phase transfer catalyst of [(C 18H37)2(CH3)2N] 7[PW11O39] has been developed for the oxidation of pyridines and alcohols with hydrogen peroxide. The reactions were conducted in 1,4-dioxane, and high yields of the corresponding heterocyclic N-oxides and ketones were obtained under relative mild conditions. The catalyst could be easily recovered and reused after reaction with cooling. There was no discernable loss in activity and selectivity after several reaction cycles.
- Ding, Yong,Zhao, Wei
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- Oxidation of organic compounds by sulfonated porous carbon and hydrogen peroxide
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The oxidation of organic compounds by sulfonated porous carbon and H 2O2 was studied at room temperature. Alkyl and aryl sulfides were oxidized to the corresponding sulfoxides or sulfones in excellent yields. Secondary alcohols were also converted to the corresponding esters/lactones and aldehydes to methyl esters in good yields. Moreover, aliphatic tertiary amines and substituted pyridines were oxidized to N-oxides.
- Shokrolahi, Arash,Zali, Abbas,Keshavarz, Mohammad Hossein
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- Green and reusable synthetic procedure for pyridine N-oxides catalyzed by a lacunary polyoxometalate
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A lacunary Keggin polyoxometalate of K8[BW11O39H] · 13H2O was used as an effective and reusable catalyst for pyridine oxidation. Good yields of pyridine N-oxides were obtained in this catalytic system with hydrogen peroxide in water under mild conditions. Taylor and Francis Group, LLC.
- Zhao, Wei,Wang, Xing,Yang, Chunxia
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- DECOMPOSITION DU PEROXYDE DE BENZOYLE DANS LES MELANGES BENZENE/X-4 PYRIDINES (X=CH3, H, CN). ETUDE CINETIQUE ET INFLUENCE DES SUBSTITUANTS SUR LA REACTIVITE NUCLEOPHILE ET RADICALAIRE DE L'ATOME D'AZOTE
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Effect of a 4-substituent in the pyridine ring upon the decomposition kinetics of benzoyl peroxide in 4-X pyridine/benzene binary mixtures (X=CH3,H,CN) has been studied.The second-order rate constant for the pyridine-induced decomposition was 2x10-6 lmol-1s-1 and in 4-methylpyridine it was 10-5 lmol-1s-1, a five-fold increase, whereas there was no nucleophilic attack on the peroxide oxygen atoms of benzoyl peroxide by 4-cyanopyridine.The surprisingly high increase of the radical-induced decomposition in 4-cyanopyridine might result from the attack at the nitrogen atom of the pyridine ring by the phenyl radical, the 1-phenylpyridinyl radical being stabilized by the cyano group.
- Vidal, S.,Court, J.,Bonnier, J.M.
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- A lipase-glucose oxidase system for the efficient oxidation of: N -heteroaromatic compounds and tertiary amines
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In this work, a lipase-glucose oxidase system has been designed and proven to be an efficient system for the oxidation of N-heteroaromatic compounds and tertiary amines. This dual-enzyme system not only displays environmental friendliness, but also demonstrates its huge potential in industrial applications.
- Yang, Fengjuan,Zhang, Xiaowen,Li, Fengxi,Wang, Zhi,Wang, Lei
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- The direct assembly of Mg-Al LDH nanosheets and Mn(ii)-salen complex into sandwich-structured materials and their enhanced catalytic properties
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The direct assembly of LDH nanosheets and organic molecules, such as Mn(ii)-salen complex, into a sandwich-structured nanocomposite has been achieved via a modified flocculation method. When used as a catalyst, the obtained material has superior thermal s
- Dai, Liyan,Zhang, Jing,Wang, Xiaozhong,Chen, Yingqi
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- Metal-free methylation of a pyridine N-oxide C-H bond by using peroxides
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Metal-free methylation of a pyridine N-oxide C-H bond was developed using peroxide as a methyl reagent under neat conditions. Pyridine N-oxide derivatives with various groups (e.g., Cl, NO2, and OCH3) were all suitable substrates, and the desired products were obtained in moderate to excellent yields under standard conditions. Moreover, the methylation can be performed with a good yield on the gram-scale experiment. Tentative mechanistic studies show that the methylation is a classical radical process.
- Li, Gang,Yang, Suling,Lv, Bingjie,Han, Qingqing,Ma, Xingxing,Sun, Kai,Wang, Zhiyong,Zhao, Feng,Lv, Yunhe,Wu, Hankui
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- Rhenium-catalyzed highly efficient oxidations of tertiary nitrogen compounds to N-oxides using sodium percarbonate as oxygen source
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Sodium percarbonate was found to be an ideal and efficient oxygen source for the oxidation of tertiary nitrogen compounds to N-oxides in excellent yields in presence of various rhenium-based catalysts under mild reaction conditions. Georg Thieme Verlag Stuttgart.
- Jain, Suman L.,Joseph, Jomy K.,Sain, Bir
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- Solvent- and halide-free synthesis of pyridine-2-yl substituted ureas through facile C-H functionalization of pyridine: N -oxides
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A novel solvent- and halide-free atom-economical synthesis of practically useful pyridine-2-yl substituted ureas utilizes easily accessible or commercially available pyridine N-oxides (PyO) and dialkylcyanamides. The observed C-H functionalization of PyO is suitable for the good-to-high yielding synthesis of a wide range of pyridine-2-yl substituted ureas featuring electron donating and electron withdrawing, sensitive, or even fugitive functional groups at any position of the pyridine ring (63-92%; 19 examples). In the cases of 3-substituted PyO, the C-H functionalization occurs regioselectively providing a route for facile generation of ureas bearing a 5-substituted pyridine-2-yl moiety.
- Rassadin, Valentin A.,Zimin, Dmitry P.,Raskil'dina, Gulnara Z.,Ivanov, Alexander Yu.,Boyarskiy, Vadim P.,Zlotskii, Semen S.,Kukushkin, Vadim Yu.
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- Visible-Light-Induced Decarboxylative Acylation of Pyridine N-Oxides with α-Oxocarboxylic Acids Using Fluorescein Dimethylammonium as a Photocatalyst
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Herein, the development of a visible-light-induced catalytic system to achieve the decarboxylative acylation of pyridine N-oxides with α-oxocarboxylic acids, at room temperature and using the organic dye fluorescein dimethylammonium as a new type of photocatalyst, is reported. A series of 2-arylacylpyridine N-oxides were selectively synthesized in moderate to good yields by controlling the polarity of the reaction solvent. The developed strategy was successfully applied in the synthesis of an important intermediate of the drug, acrivastine, on a gram scale. Notably, this is the first time that fluorescein dimethylammonium has been used to catalyze the Minisci-type C?H decarboxylative acylation reaction. The mechanism of decarboxylative acylation was studied by capturing adducts of acyl radicals and 1,1-diphenylethylene to confirm a radical mechanism. The disclosed catalytic system provides a green synthetic strategy for decarboxylative acylation without the use of additional oxidants or metal catalysts. (Figure presented.).
- Hou, Chuanfu,Sun, Shouneng,Liu, Ziqi,Zhang, Hui,Liu, Yue,An, Qi,Zhao, Jian,Ma, Junjie,Sun, Zhizhong,Chu, Wenyi
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- Oxidation of substituted pyridines by dimethyldioxirane: Kinetics and solvent effects
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The second order rate constants for the oxidation of substituted pyridines by dimethyldioxirane at 23°C in dried acetone were found to correlate with sigma values (ρ = -2.91). The reaction was shown to be very sensitive to protic, polar solvents. The oxidation of a series of substituted pyridines by dimethyldioxirane (1) produced the expected N-oxides in quantitative yields. The second order rate constants (k2) for the oxidation of a series of substituted pyridines (2a-g) by dimethyldioxirane were determined in dried acetone at 23°C. An excellent correlation with Hammett sigma values was found (ρ = -2.91, r = 0.995). Kinetic studies for the oxidation of 4-trifluoromethylpyridine by 1 were carried out in the following dried solvent systems: acetone (k2 = 0.017 M-1 s-1), carbon tetrachloride/acetone (7:3; k2 = 0.014 M-1 s -1), acetonitrile/acetone (7:3; k2 = 0.047 M-1 s-1), and methanol/acetone (7:3; k2 = 0.68 M-1 s-1). Kinetic studies of the oxidation of pyridine by 1 versus mole fraction of water in acetone [k2 = 0.78 M-1 s-1 (χ = 0) to k2 = 11.1 M-1 s-1 (χ = 0.52)] were carried out. The results showed the reaction to be very sensitive to protic, polar solvents.
- Winkeljohn, W. Rucks,Vasquez, Pedro C.,Strekowski, Lucjan,Baumstark, Alfons L.
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- Microwave activation in the synthesis of nitrogen heterocycles, N-oxides of pyridine series
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Oxidation of heterocycles of the pyridine series under conditions of microwave irradiation was studied. It is established that oxidation of pyridine and 4-methylpyridine with hydrogen peroxide results in the corresponding N-oxides, and oxidation of 3-(pip
- Khrustalev,Khamzina,Fazylov,Muldakhmetov
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- A Simple and Efficient Method for the Preparation of Heterocyclic N-Oxide
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Pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2,4-dimethylpyridine, 2,6-dimethylpyridine, quinoline, isoquinoline and 2-chloropyridine are readily oxidized to their N-oxides with a solution of trichloroisocyanuric acid, acetic acid, sodium acetate and water in acetonitrile and methylene dichloride in 78%-90% yields.
- Zhong, Ping,Guo, Sheng-Rong,Song, Cai-Sheng
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Read Online
- Carbon nanofibers decorated with oxo-rhenium complexes: Highly efficient heterogeneous catalyst for oxidation of amines with hydrogen peroxide
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Pyridine functionalized carbon nanofibers (Py-CNFs) were synthesized, characterized and used for the grafting of oxo-rhenium complex i.e., methyltrioxorhenium (MTO) via acid-base ionic interaction. The grafting of MTO to Py-CNFs was confirmed by FTIR, UV-vis, SEM, TEM and TGA analyses. The determination of rhenium content by ICP-AES further suggested the successful immobilization of MTO to the support. The developed heterogeneous material i.e., MTO@Py-CNFs was found to be an efficient catalyst for the oxidation of various secondary as well as tertiary amines to corresponding nitrones or N-oxides, respectively by using hydrogen peroxide. The developed catalyst was readily recovered by centrifugation and reused for subsequent ten runs without any significant loss in catalytic activity.
- Verma, Sanny,Kumar, Subodh,Shawat, Efrat,Nessim, Gilbert Daniel,Jain, Suman L.
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Read Online
- Oxidation of N-heterocycles by H2O2 catalyzed by a Mn-porphyrin: An easy access to N-oxides under mild conditions
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A variety of N-heteroaromatic compounds were converted into their corresponding N-oxides with good yields and with high chemoselectivity in tile presence of hydrogen peroxide as oxygen donor and a catalytic amount of Mn-porphyrin. The scope and limitation of this method are discussed.
- Thellend,Battioni,Sanderson,Mansuy
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Read Online
- From Pyridine- N-oxides to 2-Functionalized Pyridines through Pyridyl Phosphonium Salts: An Umpolung Strategy
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The reactions of pyridine-N-oxides with Ph3P under the developed conditions provide an unprecedented route to (pyridine-2-yl)phosphonium salts. Upon activation with DABCO, these salts readily serve as functionalized 2-pyridyl nucleophile equivalents. This umpolung strategy allows for the selective C2 functionalization of the pyridine ring with electrophiles, avoiding the generation and use of unstable organometallic reagents. The protocol operates at ambient temperature and tolerates sensitive functional groups, enabling the synthesis of otherwise challenging compounds.
- Bugaenko, Dmitry I.,Yurovskaya, Marina A.,Karchava, Alexander V.
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supporting information
p. 6099 - 6104
(2021/08/03)
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- Method for synthesizing pyridine-N-oxide through catalytic oxidation by continuous non-solvent method
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The invention discloses a method for synthesizing pyridine-N-oxide through catalytic oxidation by a continuous non-solvent method, and belongs to the field of chemical synthesis. The method is characterized by comprising the following steps: mixing metered pyridine or alkyl pyridine with an oxidizing agent in proportion, carrying out a reaction in a continuous tubular reactor filled with an immobilized catalyst, and distilling off excess water after the reaction is finished to obtain a pyridine-N-oxide or alkyl pyridine-N-oxide product, wherein the catalyst is cross-linked polystyrene resin immobilized with active substance anions and has a quaternary ammonium salt group. Compared with the prior art, the method for synthesizing the pyridine-N-oxide through catalytic oxidation by the continuous non-solvent method can realize continuous production of the pyridine-N-oxide, is environment-friendly, energy-saving and high in conversion rate, and has very good promotion and application values.
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Paragraph 0044-0050
(2020/08/06)
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- Method for catalyzing vitamin A isomerization with ruthenium catalyst
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The invention provides a method for catalyzing vitamin A isomer conversion with a ruthenium catalyst. According to the method, a ruthenium compound is used as a catalyst, various vitamin A cis-isomerswith low biological activity can be converted into all-trans-isomers with high biological activity in a high proportion in the presence of an auxiliary agent, and the cis-isomers comprise 9-cis-isomers, 11-cis-isomers and 13-cis-isomers. The method has the characteristics of cheap and easily available catalyst, less catalyst dosage, mild reaction conditions, low reaction cost, high isomerizationefficiency and the like.
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Paragraph 0058; 0061-0062
(2020/04/22)
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- Recyclable anhydride catalyst for H2O2 oxidation:: N -oxidation of pyridine derivatives
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The catalytic efficiency and recyclability of poly(maleic anhydride-alt-1-octadecene) (Od-MA) and poly(maleic anhydride-alt-1-isobutylene) (Bu-MA) were evaluated for use in the development of a metal-free, reusable catalyst for the oxidation of pyridines to pyridine N-oxides in the presence of H2O2. The Od-MA catalyst was easily recovered via filtration with recovery yields exceeding 99.8%. The catalyst retained its activity after multiple uses and did not require any treatment for reuse. The Od-MA and H2O2 catalytic system described herein is eco-friendly, operationally simple, and cost-effective; thus, it is industrially applicable. Od-MA and H2O2 could potentially be used in place of percarboxylic acid as an oxidant in a wide range of oxidation reactions.
- Gajeles, Ghellyn,Kim, Se Mi,Lee, Kyung-Koo,Lee, Sang Hee,Yoo, Jong-Cheol
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p. 9165 - 9171
(2020/03/13)
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- Visible-Light-Mediated C-H Alkylation of Pyridine Derivatives
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We report herein a visible-light-mediated C-H alkylation of pyridine derivatives that proceeds by simple combination of a large variety of N-alkoxypyridinium ions with alkanes in the presence of 2 mol % of fac-Ir(ppy)3 under blue illumination. The mild reaction conditions together with the high group functional tolerance make of this process a useful synthetic platform for the construction of structurally strained heterocycles. Detailed mechanistic investigations, including density functional theory calculations and quantum yield measurement, allowed us to understand factors controlling the reactivity and the selectivity of the reaction.
- Rammal, Fatima,Gao, Di,Boujnah, Sondes,Gaumont, Annie-Claude,Hussein, Aqeel A.,Lakhdar, Sami
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supporting information
p. 7671 - 7675
(2020/10/09)
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- A methyl pyridine nitrogen oxide oxidizing synthesis method
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The invention discloses an oxosynthesis method of methylpyridine-1-oxide, comprising two steps of preparation of a catalyst and oxidation reaction, wherein the preparation of the catalyst comprises the steps of after cleaning, high temperature boiling, drying and cooling pretreatment of activated carbon, adding into a phosphotungstic acid solution, stirring till complete soaking, and after ultrasonic treatment, evaporating to remove a solvent to obtain a phosphotungstic acid supported on active carbon catalyst; the oxidation reaction comprises the steps of mixing methylpyridine with the phosphotungstic acid supported on active carbon catalyst, stirring, adding hydrogen peroxide for reaction, and separating the phosphotungstic acid supported on active carbon catalyst to obtain methylpyridine-1-oxide filtrate being a methylpyridine-1-oxide crude product, and distilling under reduced pressure to obtain the product. When the method is used for preparing the catalyst, a carrier is cheap and convenient, a preparation process is simple, the catalyst in the oxidation reaction is less in use level, convenient to recycle, resuable and low in cost, product yield is up to 97%, product purity is up to 98% and productivity is more than 98%.
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Paragraph 0056; 0057; 0058
(2018/05/16)
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- A pyridine nitrogen oxide high-efficient, multi-phase catalytic preparation method
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The invention discloses a high efficient heterogeneous catalytic preparation method of pyridine oxynitride. In the provided preparation method, mono-substituted or poly-substituted pyridines or pyridine derivatives are taken as the primary raw materials, titanium dioxide loaded on tungsten (WO3/TiO2) is taken as the catalyst, hydrogen peroxide is taken as the oxidizing agent, and reactions are carried out in a water solution at a room temperature so as to obtain the target product. Compared with the prior art, the preparation method has the following advantages: (1) the provided oxidation method, no acetic acid is used, and thus the requirements on equipment are greatly reduced; (2) a heterogeneous catalytic method is adopted to prepare pyridine oxynitride, the catalyst can be separated from the reaction system through simple filtration or centrifugation, and the operation is convenient; (3) titanium dioxide loaded on tungsten is taken as the catalyst, pyridine oxynitride is prepared by one step in a water solution at a room temperature, the reaction conditions are mild, and the pollution to the environment is little.
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Paragraph 0083; 0087; 0088; 0089
(2017/08/25)
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- Visible-Light-Induced C2 Alkylation of Pyridine N-Oxides
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A photoredox catalytic method has been developed for the direct C2 alkylation of pyridine N-oxides. This reaction is compatible with a range of synthetically relevant functional groups for providing efficient synthesis of a variety of C2-alkylated pyridine N-oxides under mild conditions. Mechanistic studies are consistent with the generation of a radical intermediate along the reaction pathway.
- Zhang, Wen-Man,Dai, Jian-Jun,Xu, Jun,Xu, Hua-Jian
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p. 2059 - 2066
(2017/02/26)
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- A 4, 4 - dimethyl ° - 2, 2° - bipyridyl preparation method
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The invention discloses a preparation method of 4,4'-dimethyl-2,2'-dipyridyl, belonging to the technical field of synthesis of photosensitive catalysts of solar cells. The key points of the technical scheme are that (1) adding 4-methylpyridine into a reaction container, adding acetic acid to dissolve 4-methylpyridine, adding hydrogen peroxide with mass concentration of 30% in twice, and carrying out oxidation reaction at the room temperature, so as to prepare N-pyridine oxide; and (2) adding a palladium-carbon catalyst, heating to 60-80 DEG C, carrying out reflux to cause a coupling reaction on N-pyridine oxide, adding phosphorus trichloride to carry out deoxidization, carrying out reduced pressure suction filtration to filter out insoluble substances, and carrying out reduced pressure distillation on filtrate, so as to obtain white crystal 4,4'-dimethyl-2,2'-dipyridyl. According to the preparation method, 4-methylpyridine oxide with oxidized N atoms on a pyridine ring is directly used as an intermediate, is catalyzed and coupled by virtue of the palladium-carbon catalyst and is deoxidized by virtue of phosphorus trichloride, and the synthesis of halogenated pyridine is omitted, so that the production cost is saved; furthermore, the preparation method is relatively high in yield and applicable to industrial production.
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Paragraph 0023-0024
(2017/08/31)
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- 2,2′-Homocoupled Azine N,N′-Dioxides or Azine N-Oxides: CDC- or SNAr-Controlled Chemoselectivity
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An unprecedented Cu(OAc)2- and LiOtBu-mediated homocoupling of azine N-oxides to yield 2,2′-azine N,N′-dioxides is reported. This is the first instance in which copper has been used to catalyze the homodimerization reaction, especially of 2-phenylpyridine N-oxides. In the absence of catalytic copper, the reaction follows an alternative pathway, and instead of dioxides it yields 2,2′-azine N-monoxides. This latter protocol works efficiently with a range of N-heterocyclic oxides of pyridine, 2-phenylpyridine, quinoline and N-aryl-1,2,3-triazole. It is scalable, offers high regioselectivity and gives the products in moderate to high yields. The observed chemoselectivity between the copper-assisted and copper-free protocols is routed through oxidative cross-dehydrogenative coupling (CDC) and nucleophilic aromatic substitution of hydrogen (SNAr) pathways, respectively.
- Jha, Abadh Kishor,Jain, Nidhi
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p. 4765 - 4772
(2017/09/07)
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- Renewable waste rice husk grafted oxo-vanadium catalyst for oxidation of tertiary amines to N-oxides
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Low cost renewable waste rice husks (RH) have been used as a support for grafting of an oxo-vanadium Schiff base via covalent attachment for the oxidation of tertiary amines to N-oxide. The synthesis of the desired RH grafted oxo-vanadium complex involves prior functionalization of the RH support with amino-propyltrimethoxysilane (APTMS) followed by its reaction with salicylaldehyde to get an RH-functionalized Schiff base which subsequently reacted with vanadyl sulphate to get the targeted oxo-vanadium catalyst. The synthesized catalyst was found to be an efficient heterogeneous catalyst and afforded an excellent yield of corresponding N-oxides via oxidation of tertiary amines with hydrogen peroxide as an oxidant. Furthermore, the synthesized catalyst was found to be quite stable and showed consistent activity for five runs without any loss in activity.
- Panwar, Vineeta,Bansal, Ankushi,Ray, Siddharth S.,Jain, Suman L.
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p. 71550 - 71556
(2016/08/05)
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- The microwave-assisted ortho-alkylation of azine N-oxides with N-tosylhydrazones catalyzed by copper(i) iodide
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A copper catalyzed regioselective cross-coupling of N-tosylhydrazones with azine N-oxides to yield ortho-alkylated products in moderate to good yields is reported. The reaction is facilitated by microwave, takes place without any ligand, and uses inexpensive copper(i) iodide as the catalyst.
- Jha, Abadh Kishor,Jain, Nidhi
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supporting information
p. 1831 - 1834
(2016/02/05)
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- Structure activity relationship of pyridoxazinone substituted RHS analogs of oxabicyclooctane-linked 1,5-naphthyridinyl novel bacterial topoisomerase inhibitors as broad-spectrum antibacterial agents (Part-6)
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Abstract Oxabicyclooctane linked 1,5-naphthyridinyl-pyridoxazinones are novel broad-spectrum bacterial topoisomerase inhibitors (NBTIs) targeting bacterial DNA gyrase and topoisomerase IV at a site different than quinolones. Due to lack of cross-resistance to known antibiotics they present excellent opportunity to combat drug-resistant bacteria. A structure activity relationship of the pyridoxazinone moiety is described in this Letter. Chemical synthesis and activities of NBTIs with substitutions at C-3, C-4 and C-7 of the pyridoxazinone moiety with halogens, alkyl groups and methoxy group has been described. In addition, substitutions of the linker NH proton and its transformation into amide analogs of AM-8085 and AM-8191 have been reported. Fluoro, chloro, and methyl groups at C-3 of the pyridoxazinone moiety retained the potency and spectrum. In addition, a C-3 fluoro analog showed 4-fold better oral efficacy (ED50 3.9 mg/kg) as compared to the parent AM-8085 in a murine bacteremia model of infection of Staphylococcus aureus. Even modest polarity (e.g., methoxy) is not tolerated at C-3 of the pyridoxazinone unit. The basicity and NH group of the linker is important for the activity when CH2 is at the linker position-8. However, amides (with linker position-8 ketone) with a position-7 NH or N-methyl group retained potency and spectrum suggesting that neither basicity nor hydrogen-donor properties of the linker amide NH is essential for the activity. This would suggest likely an altered binding mode of the linker position-7,8 amide containing compounds. The amides showed highly improved hERG (functional IC50 >30 μM) profile.
- Singh, Sheo B.,Kaelin, David E.,Wu, Jin,Miesel, Lynn,Tan, Christopher M.,Meinke, Peter T.,Olsen, David B.,Lagrutta, Armando,Wei, Changqing,Liao, Yonggang,Peng, Xuanjia,Wang, Xiu,Fukuda, Hideyuki,Kishii, Ryuta,Takei, Masaya,Yajima, Masanobu,Shibue, Taku,Shibata, Takeshi,Ohata, Kohei,Nishimura, Akinori,Fukuda, Yasumichi
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p. 3636 - 3643
(2015/08/06)
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- 2,2,2-Trifluoroacetophenone as an organocatalyst for the oxidation of tertiary amines and azines to N-oxides
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A cheap, mild and environmentally friendly oxidation of tertiary amines and azines to the corresponding Noxides is reported by using polyfluoroalkyl ketones as efficient organocatalysts. 2,2,2-Trifluoroacetophenone was identified as the optimum catalyst for the oxidation of aliphatic tertiary amines and azines. This oxidation is chemoselective and proceeds in high-to-quantitative yields utilizing 10 mol% of the catalyst and H2O2 as the oxidant.
- Limnios, Dimitris,Kokotos, Christoforos G.
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supporting information
p. 559 - 563
(2014/04/03)
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- Phosphorescent light-emitting iridium complex containing pyridyltriazole ligand
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An Ir complex having a pyridyl triazole ligand substituted with at least one substituent on its pyridyl ring, and a light emitting material comprising such Ir complex. Such light emitting material was found to have a significantly enhanced photophosphorescence quantum yield and hypsochromic blue shifted photophosphorescent emission over other Ir complexes with a pyridyl triazole ligand having no substituent in its pyridine ring. Use of such light emitting material and an organic light emitting device including the same.
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- Mild and recyclable catalytic oxidation of pyridines to N-oxides with H2O2 in water mediated by a vanadium-substituted polyoxometalate
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A vanadium-substituted polyoxometalate, K6[PW9V 3O40]·4H2O, was used as a recyclable and effective catalyst for the oxidation of pyridines. The reactions were successfully conducted in water under mild conditions. The catalyst could be easily recovered and reused.
- Ding, Yong,Zhao, Wei,Song, Wenfeng,Zhang, Zhenxin,Ma, Baochun
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supporting information; experimental part
p. 1486 - 1489
(2011/08/03)
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- SOLID PHASE REACTION SYSTEM FOR OXIDATION
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A solid phase reaction system for oxidation of an organic compound, having high industrial value in which an organic solvent exerting a reverse influence on earth environments is not necessary, reuse of a catalyst is possible, and high yield can be attained, comprising a mixture of a powdery dispersion medium and a powder of a solid catalyst for the above-described oxidation reaction, and the above-described organic compound and aqueous hydrogen peroxide,wherein the above-described organic compound, the above-described solid catalyst and the above-described aqueous hydrogen peroxide are dispersed in the above-described mixture so that they get into contact mutually.
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Page/Page column 7
(2010/05/13)
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- Equilibrium of acyl transfer between pyridine N-oxides and their acylonium salts
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Transfer of acyl groups from N-acyloxypyridinium salts to pyridine N-oxides in acetonitrile was studied. The equilibrium constants of acyl exchange were determined. These quantities vary in the range covering eight orders of magnitude, depending on the st
- Rubachenko,Schroeder,Chotii,Kovalenko,Red'ko,Lenska
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p. 1241 - 1246
(2008/12/22)
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- Facile, one-step production of niacin (vitamin B3) and other nitrogen-containing pharmaceutical chemicals with a single-site heterogeneous catalyst
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Niacin (3-picolinic acid), which is extensively used as vitamin B 3 in foodstuffs and as a cholesterol-lowering agent, along with other oxygenated products of the picolines, 4-methylquinoline, and a variety of pyrimidines and pyridazines, may be produced in a single-step, environmentally benign fashion by combining single-site, open-structure, heterogeneous catalysts witha solid source of active oxygen, namely acetyl peroxyborate (APB), in the absence of an organic solvent. The high activities, selectivities, and the relatively mild conditions employed with this single-site heterogeneous catalyst, coupled with ease of transport, storage, and stability of the solid oxidant, augurs well for the future use of APB in conjunction with other open-structure, single-site catalysts for fine-chemical, pharmaceutical, and agrochemical applications.
- Raja, Robert,Thomas, John Meurig,Greenhill-Hooper, Michael,Ley, Steven V.,Almeida Paz, Filipe A.
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experimental part
p. 2340 - 2348
(2009/04/11)
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- SELECTIVE OXIDATION OF ORGANIC COMPOUNDS
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This invention relates to the selective oxidation of organic compounds. According to the invention organic compounds are selectively oxidized using a peracid or a source of peracid, a transition metal based heterogeneous catalysts and a borate or boric acid in the presence of water. Using the process of the present invention, both excellent conversion and product selectivity maybe obtained.
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Page/Page column 24-27
(2008/06/13)
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- Rate and equilibrium constants of benzoyl group transfer between pyridine N-oxides
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Kinetic characteristics of 19 transfer reactions of benzoyl group from N-benzoyloxypyridinium salts to pyridine N-oxides and 4-dimethylaminopyridine were studied in acetonitrile by the stopped-flow method. The rate of an identical reaction for 4-methoxypyridine was measured by dynamic NMR spectroscopy. For 5 other identical reactions the rates were estimated from Bronsted correlations. Equilibrium constants were estimated with the use of UV spectrophotometry (6), IR spectroscopy (2), from kinetic data (K ij = k ij /k ji ) (2), and in one case as logK i-j = logK i-x - logK j-x . The second order rate constants (k ij ) varied in the range 102-105 l mol -1 s-1, the equilibrium constants (K ij ) in the range 102-10-2; the activation parameters (ΔH ≠) were within 15-50 kJ mol-1, (-ΔS ≠) -20-110 J mol-1 K-1. The reactions under study occur in a single stage following the concerted SN2 mechanism through an early associative transition state. The benzoyl groups exchange rate and equilibrium are well described by simplified Marcus equation (omitting the quadratic term). 2005 Pleiades Publishing, Inc.
- Rybachenko,Schroeder,Chotii,Lenska,Red'Ko,Kovalenko
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p. 774 - 778
(2007/10/03)
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- Aqueous biphasic oxidation: A water-soluble polyoxometalate catalyst for selective oxidation of various functional groups with hydrogen peroxide
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A "sandwich" type polyoxometalate, Na12[(WZn 3(H2O)2][(ZnW9O34) 2], was used as an oxidation catalyst in aqueous biphasic reaction media to effect oxidation of alcohols, diols, pyridine derivatives, amines and aniline derivatives with hydrogen peroxide. The catalyst was shown by 183W NMR to be stable in aqueous solutions in the presence of H 2O2 and showed only minimal non-productive decomposition of the oxidant. Secondary alcohols were selectively oxidized to ketones, while primary alcohols tended to be oxidized to the corresponding carboxylic acids, although secondary alcohols were selectively oxidized in the presence of primary alcohols. Vicinal diols yielded carbon-carbon bond cleavage products in very high yields. Pyridine derivatives were oxidized to the respective TV-oxides, but strongly electron-withdrawing moieties inhibited the oxidation reaction. Primary amines were oxidized to the oximes, but significantly hydrolyzed in situ. Aniline derivatives were oxidized to the corresponding azoxy or nitro products depending on the substitution pattern in the aromatic ring. Catalyst recovery and recycle was demonstrated.
- Sloboda-Rozner, Dorit,Witte, Peter,Alsters, Paul L.,Neumann, Ronny
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p. 339 - 345
(2007/10/03)
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