- Aliphatic nitro compounds chemistry: oximes–nitrones tunable production through directed tandem synthesis
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Abstract: Reduction of aliphatic nitro compounds in the presence of aldehydes and dialdehydes for tunable directed synthesis of oximes, nitrones, nitrone–oximes, and dinitrones was reported. The slow and nonselective reduction of aliphatic nitro compounds was directed by condensation of in situ prepared alkylhydroxylamines with aromatic aldehydes. Mononitrones and dinitrones were synthesized at reflux and at 55?°C conditions, respectively, in tetrahydrofuran using SnCl2?2H2O and Na2CO3. It was found that the presence of a catalytic amount of carboxylic acid such as 3-phenylpropanoic acid increases the yield of dinitrones versus nitrone–oxime and dioxime when dialdehydes were used as aldehyde source. Graphical abstract: [Figure not available: see fulltext.].
- Kazemi, Foad,Ramdar, Moosa,Davarpanah, Jamal
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p. 353 - 362
(2019/01/25)
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- RuO4-mediated oxidation of secondary amines. Part 1. Are hydroxylamines the main intermediates?
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The RuO4-catalyzed oxidation of secondary amines Bn-NH-CH2R (1a and b; R=H, Me) gave mainly amides, but minute amounts of nitrones PhCH=N(O)-CH2R (9a and b) and traces of Bn-N(OH)-CH2R (R=H, 4a) were also detect
- Florea, Cristina A.,Petride, Horia
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p. 475 - 486
(2016/07/20)
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- 1-Cyanoformamidines. Formation during the RuO4-mediated oxidation of secondary amines
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When performed in the presence of cyanide and at pH smaller than 5, the RuO4-mediated oxidation of secondary amines Bn-NH-R (1a-b; R=Me, Et) gave mainly 1-cyanoformamidines Bn-NR-C(=NH)-CN (2a-b) and their hydrolysis products Bn-NR-COCN (3a-b), Bn-NR-CN (4a-b), Bn-NR-CONH2 (5a-b). Carboxamides 5a-b can result also directly from 1a-b. (Chemical Equation Presented).
- Florea, Cristina,Stavarache, Cristina,Petride, Horia
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p. 319 - 325
(2016/10/11)
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- Stereoselective synthesis of fluoroalkenoates and fluorinated isoxazolidinones: N-substituents governing the dual reactivity of nitrones
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α-Fluoroalkenoates and 4-fluoro-5-isoxazolidinones are of vast interest due to their potential biological applications. We now demonstrate the syntheses of (E)-α-fluoroalkenoates and 4-fluoro-5-isoxazolidinones by the reactions between nitrones and α-fluoro-α-bromoacetate. By altering N-substituents in nitrones, (E)-α-fluoroalkenoates and 4-fluoro-5-isoxazolidinones can be achieved, respectively, with high chemo- and stereoselectivities. Experimental and computational studies have been conducted to elucidate the reaction mechanisms. Linear free energy relationship studies further revealed that the N-substituent effects are primarily of electronic origin. Copyright
- Prakash, G.K. Surya,Zhang, Zhe,Wang, Fang,Rahm, Martin,Ni, Chuanfa,Iuliucci, Marc,Haiges, Ralf,Olah, George A.
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supporting information
p. 831 - 838
(2014/01/23)
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- Molybdenum oxide/bipyridine hybrid material {[MoO3(bipy)] [MoO3(H2O)]}n as catalyst for the oxidation of secondary amines to nitrones
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The inorganic-organic hybrid material {[MoO3(bipy)][MoO 3(H2O)]}n (bipy = 2,2′-bipyridine) can be used as a water-tolerant catalyst for the oxidation of secondary amines under mild conditions using either urea hydrogen peroxide (UHP) or tert-butylhydroperoxide (TBHP) as the oxidant. Under optimized reaction conditions (2 mol % catalyst, 3-4 equiv TBHP, CH2Cl2 as the solvent, 40 °C), the corresponding nitrones were obtained with different efficiency depending on the nature of the cyclic or acyclic amine used.
- Abrantes, Marta,Gonalves, Isabel S.,Pillinger, Martyn,Vurchio, Carolina,Cordero, Franca M.,Brandi, Alberto
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experimental part
p. 7079 - 7082
(2012/01/30)
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- Oxidation of secondary amines by molecular oxygen and cyclohexanone monooxygenase
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Cyclohexanone monooxygenase from Acinetobacter calcoaceticus catalyzed the oxidation of tertiary and secondary amines to N-oxides and nitrones, respectively. The formation of a hydroxylamine intermediate was involved with secondary amines as starting substrates.
- Colonna, Stefano,Pironti, Vincenza,Carrea, Giacomo,Pasta, Piero,Zambianchi, Francesca
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p. 569 - 575
(2007/10/03)
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- Oxidation of amines catalyzed by cyclohexanone monooxygenase
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Cyclohexanone monooxygenase catalyzed the oxidation of tertiary, secondary and hydroxylamines to N-oxides, hydroxylamines and nitrones respectively.
- Colonna, Stefano,Pironti, Vincenza,Pasta, Piero,Zambianchi, Francesca
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p. 869 - 871
(2007/10/03)
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- Regiochemistry and mechanism of oxidation of N-benzyl-N-alkylhydroxylamines to nitrones
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The oxidation of various N-(o-, m-, p-substituted benzyl)-N-alkylhydroxylamines and their dideuteriobenzyl (PhCD2) counterparts was carried out using mercury(II) oxide and p-benzoquinone (p-BQ) as oxidants. An overwhelming preference for the formation of conjugated nitrones is observed in the oxidation of N-benzyl-N-isopropylhydroxylamines. Considerable intra- and intermolecular kinetic isotope effects and negative ρ values in the Hammet plots point towards a mechanistic pathway that involves electron transfer from nitrogen to the oxidant followed by hydrogen abstraction. The conformation of unstable (E)-nitrones, which readily isomerize to the more stable (Z)-nitrones, is deduced from 1H NMR data. The E ? Z isomerization was found to be a bimolecular process. Copyright
- Hassan, Azfar,Wazeer, Mohammed I. M.,Saeed, Mohammed T.,Siddiqui, Mohammad N.,Ali, Sk. Asrof
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p. 443 - 451
(2007/10/03)
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- Regioselective synthesis of nitrones by decarboxylative oxidation of N- alkyl-α-amino acids and application to the synthesis of 1-azabicyclic alkaloids
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Tungstate-catalyzed oxidation of N-alkyl-2a-amino acids with 30% H2O2 solution under phase-transfer conditions gives nitrones regioselectively in good yields: Using this method, stereodivergent synthesis of (R)- and (S)-4- (t-butyldimethylsilyloxy)-1-pyrroline N-oxides ((R)-17a and (S)-17a) was achieved. In addition, (R)- and (S)-3-(t-butyldimethylsilyloxy)-1-pyrroline N-oxides ((R)-45 and (S)-45) were prepared by catalytic oxidation of the corresponding chiral pyrrolidines in a regioselective manner. These chiral cyclic nitrones, 17 and 45 are versatile intermediates for the synthesis of optically active nitrogen heterocycles, since stereoselective additions of carbon nucleophiles to these chiral nitrones can be readily performed. Typically, ZnI2-mediated addition of ketene t-butyldimethylsilyi methyl acetal (29a): to (R)-17a gave the' cis-adduct, methyl (2R,4R)-[1,4-bis(t- butyldimethylsilyloxy)pyrrolidin-2-yl]acetate (cis-30). In contrast, the addition of lithium acetylides 34 to the nitrone (R)-17a gave the trans- adducts, (2S,4R)-2-(1-alkynyl)-4-(t-butyldimethylsilyloxy)-1- hydroxypyrrolidines trans-35. These adducts are useful intermediates for syntheses of the nitrogen heterocycles (3R,5R)-1-aza-3- hydroxybicyclo[3.3.0]octane (37) and (6R,8R)-1-aza-8- hydroxybicyclo[4.30]nonane (38), respectively. The ZnI2-mediated addition of ketene silyl acetal 29a to the nitrone (R)-45 gave methyl (2S, 3R)-[1,3- bis(t-butyldimethylsilyloxy)pyrrolidin-2-yl]acetate (trans-50a), which was used for asymmetric synthesis of the Geissman-Waiss lactone ((-)-49).
- Ohtake, Hiroaki,Imada, Yasushi,Murahashi, Shun-Ichi
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p. 2737 - 2754
(2007/10/03)
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- Methyltrioxorhenium-Catalyzed Oxidation of Secondary and Primary Amines with Hydrogen Peroxide
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The methyltrioxorhenium-catalyzed oxidation of secondary amines and primary amines with hydrogen peroxide has been carried out. The oxidation of secondary amines afforded nitrones in good-to-excellent yield. Benzylamines were selectively oxidized to oximes, while general primary alkylamines possessing the α-C -H bond gave mixtures of oximes, nitroso dimers, and azoxy compounds.
- Yamazaki, Shigekazu
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p. 877 - 883
(2007/10/03)
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- Tungstate-Catalyzed Decarboxylative Oxidation of N-Alkyl-α-amino Acids: An Efficient Method for Regioselective Synthesis of Nitrones
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The tungstate-catalyzed oxidation of N-alkyl-α-amino acids with hydrogen peroxide under phase-transfer conditions gives the corresponding nitrones in satisfactory yield.
- Murahashi, Shun-Ichi,Imada, Yasushi,Ohtake, Hiroaki
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p. 6170 - 6172
(2007/10/02)
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- Nitrones from Addition of Benzyl and Allyl Grignard Reagents to Alkyl Nitro Compounds: Chemo-, Regio-, and Stereoselectivity of the Reaction
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Reaction of allyl and benzyl Grignard reagents with functionalized nitroalkanes afford nitrones in good yield.This process shows considerable chemoselectivity; carbonyl groups and other highly reactive electrophilic functions are unaffected by the reaction conditions (THF, -70 deg C).A mixture of regioisomers 4 and 5 is usually obtained, and the product distribution depends on the nature of the alkyl framework.An intermediate 3 is postulated, and the isomeric pair of nitrones arises, very likely through a selective syn elimination. α-Substituted alkyl chains give mostly conjugated products 4 while unbranched chains afford predominantly the nonconjugated nitrones 5.The 4/5 ratio can be strongly modified by using a proton source of suitable strength; trichloroacetic acid produces 4 exclusively in the reaction of nitroethane with benzyl Grignard, while 2,6-dimethylphenol affords completely the nonconjugated nitrone 5.The stereochemistry of the double bond is affected by the nature of the reagent used.Benzyl Grignard gives only Z nitrones 4 and 5; 2-butenylmagnesium chloride gives nonconjugated Z nitrones and a predominance of E isomer in the conjugated nitrone 5.
- Bartoli, Giuseppe,Marcantoni, Enrico,Petrini, Marino
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p. 5834 - 5840
(2007/10/02)
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- A CONVENIENT SYNTHESIS OF NITRONES BY N-ALKYLATION OF O-TRIMETHYLSILYLOXIMES
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Aldoxime and ketoxime-O-trimethylsilyl ethers can be alkylated with trialkyl-oxonium tetrafluoroborates and alkyl triflates at or below room temperature to produce nitrones in good yields.
- LeBel, Norman A.,Balasubramanian, N.
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p. 4331 - 4334
(2007/10/02)
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