- 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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p. 1843 - 1849
(2018/07/06)
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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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- Amines vs. N-Oxides as Organocatalysts for Acylation, Sulfonylation and Silylation of Alcohols: 1-Methylimidazole N-Oxide as an Efficient Catalyst for Silylation of Tertiary Alcohols
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A comparison of the relative catalytic efficiencies of Lewis-basic amines vs. N-oxides for the acylation, sulfonylation and silylation of primary, secondary and tertiary alcohols is reported. Whilst the amines are generally superior to the N-oxides for acylation, the N-oxides are superior for sulfonylation and silylation. In particular, 1-methylimidazole N-oxide (NMI-O) is found to be a highly efficient catalyst for sulfonylation and silylation reactions. To the best of our knowledge, NMI-O is the first amine or N-oxide Lewis basic organocatalyst capable of promoting the efficient silylation of tert-alcohols in high yield with low catalyst loading under mild reaction conditions.
- Murray, James I.,Spivey, Alan C.
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p. 3825 - 3830
(2016/01/25)
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- Highly efficient and selective phosphorylation of amino acid derivatives and polyols catalysed by 2-aryl-4-(dimethylamino)pyridine-N-oxides-towards kinase-like reactivity
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The chemoselective phosphorylation of hydroxyl containing amino acid derivatives and polyols by phosphoryl chlorides catalyzed by 2-aryl-4-(dimethylamino)pyridine-N-oxides is described.
- Murray, James I.,Woscholski, Rudiger,Spivey, Alan C.
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p. 13608 - 13611
(2015/01/09)
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- Method of synthesis of tetradentate amide macrocycle ligand and its metal-complex
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A tetradendate amide based macrocyclic ligand and its Fe(III) complex which act as activators of hydrogen peroxide. The synthetic methodology to develop the ligands is new, simple and provides better yield for each step of the ligand synthesis. The Fe(III
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Page/Page column 3
(2011/05/05)
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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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- Identical acyl transfer reactions between pyridine N-oxides and their N-acylonium salts
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28 identical acyl exchange reactions R-CO-Nu+, X- + Nu between pyridine N-oxides in acetonitrile were studied. Here, X- = BPh 4 - and R = methyl, N,N-dimethylamino, N,N-diethylamino, 4-morpholino, 1-piperidino, N-methyl, N-phenylamino, or N,N-diphenylamino group. The IR and NMR spectroscopic characteristics of acyloxypyridinium salts were determined, and the quantum-chemical parameters of all reagents calculated. The results were subjected to correlation analysis. It was found that the rate of identical acyl transfer reactions was controlled by the interaction of frontier orbitals in the transition state.
- Rybachenko,Shroeder,Chotii,Kovalenko,Red'Ko,Gierzyk
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p. 1608 - 1612
(2008/03/14)
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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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- The Rate and Equilibrium Constants for N-, O-Acyl Transfer
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Reactions with dimethylcarbamoyl group transfer from N-acylpyridinium salts to pyridine N-oxides and from N-acyloxypyridinium salts to pyridines in acetonirile solutions were studied. Their rate and equilibrium constants and activation parameters were determined. The reactions were shown to be one-step and to follow the SN2 mechanism. Equations relating the rate and equilibrium parameters of the N-O and O-N acyl transfer reactions to the basicity of the nucleophile and outgoing group were obtained.
- Rybachenko,Chotii,Kovalenko,Shreder
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p. 1695 - 1698
(2007/10/03)
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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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p. 786 - 788
(2007/10/03)
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- Acetyl exchange between pyridine N-oxides in acetonitrile solutions: An attempt to apply the Marcus equation to acetyl transfer
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Forty-three (including eight identical) reactions of acetyl transfer from N-acetyloxypyridinium salts to pyridine N-oxides in acetonitrile solutions were studied. The rate constants k2 vary in the range 107-10-1 1 mol-1 s-1; the equilibrium constants K, in the range 107-10-7; the activation enthalpy ΔH≠, in the range 17-30 kJ mol-1; the activation entropy -ΔS≠, in the range 60-85 J mol-1 K-1; and the heat of reaction -ΔH0, within ±50 kJ mol-1. All reactions occur in a single stage by the concerted SN2 mechanism with a low degree of bond cleavage in the transition state. The rate and equilibrium of the acetyl exchange are satisfactorily described by the Bronsted equation. The quality of predicting the reactivity is substantially improved by introducing into the correlation equation a second parameter, the rates of identical reactions.
- Rybachenko,Schroeder,Chotii,Titov,Kovalenko,Leska,Grebenyuk
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p. 1608 - 1615
(2007/10/03)
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- Tertiary amine oxidation using HOF-CH3CN: A novel synthesis of N-oxides
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HOF·CH3CN, probably the best oxygen transfer agent organic chemistry has to offer, is easily made by bubbling diluted fluorine (10-15%) through aqueous acetonitrile solution. Used as formed without any isolation or purification, it reacts with various tertiary amines such as pyridine derivatives, polyaromatic nitrogen containing compounds and aliphatic and alicyclic ones to form the corresponding N-oxides. When two nitrogen atoms are present it is possible to make both the N-monoxides and the N,N-dioxides. The reaction times are short (a few minutes), conditions are very mild (0-25 °C) and the yields range from good to excellent (70-95%).
- Dayan, Sharon,Moshe, Kol,Rozen, Shlomo
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p. 1427 - 1430
(2007/10/03)
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- Formation of Singlet Oxygen in the Deoxygenation of Heteroarene N-Oxides by Dimethyldioxirane
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4-Dimethylaminopyridine-N-oxide 2 and 2',3',5'-triacetyladenosine-N1-oxide 4 are partially deoxygenated by dimethyldioxirane (DMD) to the corresponding amines 1 and 3; the formation of singlet oxygen suggests a polar rather than a radical mechanism, in which we propose SN2 attack of the N-oxide on the dioxirane peroxide bond.
- Adam, Waldemar,Briviba, Karlis,Duschek, Frank,Golsch, Dieter,Kiefer, Wolfgang,Sies, Helmut
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p. 1831 - 1832
(2007/10/02)
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- NUCLEOPHILIC CATALYSIS OF THE AMINOLYSIS OF ACTIVATED VINYL HALIDES BY ORGANIC BASES
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The existence of nucleophilic catalysis in the aminolysis of activated vinyl halides has been revealed.The limits and conditions of catalysis have been established from the results of a stepwise investigation of the kinetics of the processes occurring (the rate is limited by the formation or consumption of the intermediate vinylammonium salt).The nucleophilic catalysts studied form the following series in the efficiency of their action in SNVin-substitution involving amines in acetonitrile: 4-isopropylpyridine > pyridine > trimethylamine > 4-N,N-dimethylaminopyridine N-oxide > N-methylimidazole > N-methylpiperidine.
- Kravchenko, V. V.,Popov, A. F.,Kotenko, A. A.
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p. 1601 - 1605
(2007/10/02)
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- New description of substituent effect on electronic spectra by means of substituent constants-VI. Ultraviolet spectra of 4-substituted pyridine N-oxides and blue shifted iodine bands of their EDA complexes with iodine
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Electronic spectra of 4-substituted pyridine N-oxides and their EDA complexes with iodine were studied.The substituent effect on the near u.v. 1A1 intramolecular CT bands of the N-oxides and on the blue shifted iodine bands caused by CT complex formation are discussed in terms of a general equation, theoretically derived in order to describe the substituent effect on electronic spectra by means of substituent constants.The results are quite successful and supported by semi-empirical SCFMO-Cl calculations.Based on the results mentioned above, the character of n-? type N-oxide-iodine CT complexes is also examined.The complex formation constants(log K) and pKa values of the N-oxides correlate especially well, indicating that the CT interaction mechanism cannot be neglected in proton addition reactions such as hydrogen bonding and pKa values.
- Uno, Bunji,Kano, Kenji,Kaida, Naoki,Kubota, Tanekazu
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p. 937 - 944
(2007/10/02)
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- Catalytic Rearrangement of O,S-Dialkyl Dithiocarbonates to S,S-Dialkyl Dithiocarbonates by Pyridine N-Oxides. The Reaction Mechanism
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The reaction of O-alkyl S-methyl dithiocarbonates (xanthates) (I) with pyridine N-oxides (II) gave the corresponding S-alkyl S-methyl dithiocarbonates (dithiolcarbonate) (III) together with the symmetric S,S-dialkyl and S,S-dimethyl dithiocarbonates in good yields.Pyridine N-oxides bearing electron-donating substituents are efficient catalysts for rearrangement of I to III.The reaction is pseudo-first-order and the apparent first-order rate constant is proportional to the concentration of II.The role of pyridine N-oxides and the reaction behavior of O,S-dialkyldithiocarbonates are discussed on the basis of kinetic and molecular orbital calculation data.The rearrangement may proceed by nucleophilic attack of -SCOSR derived from a complex of I and II on the O-alkyl group of xanthates.The reaction provides a useful preparation method for alkanethiols by aminolysis of the products with ethanolamine.Keywords O,S-dialkyl dithiocarbonate; S,S-dialkyl dithiocarbonate; pyridine N-oxide; thiol; charge transfer; catalytic rearrangement; kinetics; ethanolamine; frontier molecular orbital
- Harano, Kazunobu,Shinohara, Ikuo,Sugimoto, Shin-ichiro,Matsuoka, Toshikazu,Hisano, Takuzo
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p. 576 - 581
(2007/10/02)
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- The Equilibrium in the Formation of N-acetoxypyridinium Salts
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The interaction of pyridine N-oxides with acetyl chloride and acetyl bromide has been investigated in chloroform, methylene chloride, and acetonitrile.The equilibrium constants and the thermodynamic characteristics of the formation of N-acetoxypyridinium salts have been obtained.
- Rybachenko, V. I.,Chotii, K. Yu.,Kozhevina, L. I.,Titov, E. V.
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p. 813 - 816
(2007/10/02)
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