- Dipole-stabilized carbanions in the series of cyclic aldonitrones 3. The influence of the configuration of the nitrone group on H-D exchange of the methine hydrogen atom and metallation of aldonitrones
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The spin-spin coupling constants 3JC,H between the hydrogen atom of the aldonitrone group and the carbon atom bound to the nitrogen atom of the N-oxide fragment were determined for a wide range of cyclic and acyclic aldonitrones. Based on comparison of these constants (trans-3JC,H (E isomer) > cis-3JC,H (Z isomer)), the Z configuration was assigned to acyclic nitrones. Coordination of organolithium compounds to the oxygen atom of the N->O group was revealed by 13C NMR spectroscopy. This coordination is the necessary condition for the metallation of aldonitrones. The configuration of the nitrone group is responsible for the ability of the F form of acyclic aldonitrones to undergo CD3ONa-catalyzed isotope exchange of the methine proton in CD3OD and metallation with BusLi.
- Voinov, M. A.,Grigor'ev, I. A.
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- 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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- Carbamoyl anion addition to nitrones
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The addition of carbamoyl anions derived from N,N-disubstituted formamides and LDA to N-tert-butyl nitrones is described. The reaction was demonstrated with a variety of formamides and nitrones and provided a direct route to α-(N-hydroxy)amino amides. The use of a tert-leucinol derived chiral auxiliary on the nitrone provided products in good diastereoselectivity. Derivatization of the products by tert-butyl deprotection or N-deoxygenation was demonstrated.
- Reeves, Jonathan T.,Lorenc, Chris,Camara, Kaddy,Li, Zhibin,Lee, Heewon,Busacca, Carl A.,Senanayake, Chris H.
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p. 5895 - 5902
(2014/07/08)
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- Exploiting microwave-assisted neat procedures: synthesis of N-aryl and N-alkylnitrones and their cycloaddition en route for isoxazolidines
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Microwave irradiation allows increasing the speed of several reactions and also offers the possibility of eliminating poisoning organic solvents. In this work we report the microwave-assisted neat synthesis of α-phenyl-tert-butylnitrone (PBN) and other alkyl and aryl nitrones and also the rapid synthesis of isoxazolidines resulting from 1,3-dipolar cycloaddition of nitrones to ethyl trans-crotonate.
- Andrade, Marta M.,Barros, Maria Teresa,Pinto, Rui C.
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p. 10521 - 10530
(2008/12/23)
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- A novel route to substituted 4-methylene-4,5-dihydroisoxazoles mediated by hafnium(IV) chloride
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Heating alkyl vinyl ketones and N-tert-butylarylmethylide-neamine N-oxides in the presence of HfCl4 results in the formation of 4-methylene-4,5-dihydroisoxazoles in good yield.
- Dunn,Graham,Grigg,Higginson,Sridharan,Thornton-Pett
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p. 1968 - 1969
(2007/10/03)
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- Chromium and Tungsten Pentacarbonyl Groups as Reactivity and Selectivity Auxiliaries in Cycloaddition of Alkynyl Fischer Carbene Complexes with N-Alkyl Nitrones
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Alkynyl Fischer carbene complexes were found to undergo chemoselective, regioselective, and rate-enhanced 1,3-dipolar cycloaddition with nitrones to give 2,3-dihydroisoxazole carbene complexes in excellent yields.These alkynyl complexes can serve as synth
- Chan, Kin Shing,Yeung, Ming Lok,Chan, Wai-kin,Wang, Ru-Ji,Mak, Thomas C. W.
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p. 1741 - 1747
(2007/10/02)
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- Synthesis and Characterization of Phenyl-Substituted C-Phenyl-N-tert-butylnitrones and Some of Their Radical Adducts
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Synthesis of C-phenyl-N-tert-butylnitrone (PBN) and several of its analogues with substituents in the 2-, 3-, or 4-position on the phenyl ring is described.While a one-pot reduction/condensation method proved suitable for the most compounds, it was necessary to prepare some examples by direct condensation or through oxidation of the appropriate imine.The 1H NMR data for the 3-X- and 4-X-PBN's can be correlated with the Hammett equation.For the 3-X series Δδ for the α-proton correlates best with ?+ and has a correlation coefficient of 0.90.For the 4-X series a dual substituent parameter equation using ?R0 gives the best correlation with r = 0.99.The hyperfine splitting constants (hfsc's) of HO and HOO adducts of serveral substituted PBN's are also included and their correlation with the Hammett equation is discussed.
- Hinton, Randall D.,Janzen, Edward, G.
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p. 2646 - 2651
(2007/10/02)
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- Imines and Derivatives. Part 24. Nitrone Synthesis by Imine Oxidation using either a Peroxyacid or Dimethyldioxirane
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The oxidation of N-alkyl imines by m-chloroperoxybenzoic acid to yield nitrones was facilitated by (i) the presence of C-aryl substituents, (ii) steric inhibition of attack at the imino C-atom, (iii) electron donating para-substituents on the C-aryl substituent, (iv) non-hydroxylic solvents, (v) optimal conjugation between C-aryl substituents and the imino group, and (vi) less bulky N-alkyl groups. The oxidation of N-alkyl imines by dimethyldioxirane (DMD) in dichloromethane-acetone solution yielded nitrones without evidence of oxaziridine formation.The yields of isolated nitrones were higher for C,C-diaryl imines and for imines bearing less bulky N-alkyl substituents.N-H substituted ketimines were found to yield oximes after reaction with dimethyldioxirane.
- Boyd, Derek R.,Coulter, Peter B.,McGuckin, M. Rosaleen,Sharma, Narain D.,Jennings, W. Brian,Wilson, Valerie E.
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p. 301 - 306
(2007/10/02)
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- NORMAL, ABNORMAL AND PSEUDO-ABNORMAL REACTION PATHWAYS FOR THE IMINE-PEROXYACID REACTION
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Steric and mesomeric effects have a marked influence upon the formation of oxaziridine (normal pathway) or nitrone (abnormal pathway) products from the imine-peroxyacid reaction; n.m.r. studies of the thermal isomerization of oxaziridines to nitrones prov
- Boyd, Derek R.,Coulter, Peter B.,Sharma, Narain D.,Jennings, Brian W.,Wilson, Valerie E.
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p. 1673 - 1676
(2007/10/02)
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- INFLUENCE OF LAMELLAR LIQUID CRYSTALLINE MEDIA IN THE HYDROLYSIS OF 4-SUBSTITUTED BENZYLIDENE t-BUTYLAMINE N-OXIDES.
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Cationic lamellar liquid crystalline morphologies decrease the rate of hydrolysis of a series of 4-substituted benzylidene t-butylamine N-oxides compared to aqueous solutions. Rate constants for the aqueous acid hydrolysis decrease as the electron releasing effect increases and they are linear when plotted against sigma ** plus -substitutent constants. Rho-values indicate a less sensitive reactivity series than the benzoic acids and a more sensitive reactivity in lamellar solvents. Reaction rates for the series in the latter solvent parallel the hydrophobic substituent constants. Three different lamellar morphologies were identified in the aqueous surfactant systems.
- Bacon,Neubert,Wildman,Ott
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p. 307 - 321
(2007/10/02)
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