- Building Congested Ketone: Substituted Hantzsch Ester and Nitrile as Alkylation Reagents in Photoredox Catalysis
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For the first time, 4-alkyl Hantzsch esters were used to construct molecules with all-carbon quaternary centers by visible light-induced photoredox catalysis via transfer alkylation. Up to a 1500 h-1 turnover frequency was achieved in this reaction. Reactions of 4-alkyl Hantzsch nitriles as tertiary radical donors joined two contiguous all-carbon quaternary centers intermolecularly, and this chemistry was used to synthesize a common precursor of a class of hydroxysteroid dehydrogenase inhibitors.
- Chen, Wenxin,Liu, Zheng,Tian, Jiaqi,Li, Jin,Ma, Jing,Cheng, Xu,Li, Guigen
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supporting information
p. 12312 - 12315
(2016/10/07)
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- Benzylation of nitroalkanes using copper-catalyzed thermal redox catalysis: Toward the facile C-alkylation of nitroalkanes
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The C-alkylation of nitroalkanes under mild conditions has been a significant challenge in organic synthesis for more than a century. Herein we report a simple Cu(I) catalyst, generated in situ, that is highly effective for C-benzylation of nitroalkanes using abundant benzyl bromides and related heteroaromatic compounds. This process, which we believe proceeds via a thermal redox mechanism, allows access to a variety of complex nitroalkanes under mild reaction conditions and represents the first step toward the development of a general catalytic system for the alkylation of nitroalkanes.
- Gildner, Peter G.,Gietter, Amber A. S.,Cui, Di,Watson, Donald A.
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supporting information; experimental part
p. 9942 - 9945
(2012/08/07)
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- Kinetic studies of the reaction of some nitrosoalkanes with nitrogen dioxide
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The rates of the oxidation of some nitrosoalkanes (CH3)2C(CH2X)NO by nitrogen dioxide in carbon tetrachloride have been studied by stopped-flow techniques, and have been found to exhibit second order kinetics. Arrhenius parameters have been determined for the cases of X = H, CH3, C(CH3)3, C6H5, NO2, Cl and OCOCH3. Electron withdrawing substituents are found to decrease significantly the rates, which are generally much faster than the corresponding oxidation of nitrosoarenes. The results obtained are discussed with reference to the Hammett σ constants of the substituents X, and the atomic charges at the nitrogen atom as given by the TNDO/2 method, the geometries of the molecules having been optimised by the PM3 semi-empirical method.
- Gowenlock, Brian G.,King, Boyd,Pfab, Josef,Witanowski, Michal
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p. 483 - 485
(2007/10/03)
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- Oxidation potential as a measure of the reactivity of anionic nucleophiles. Behaviour of different classes of nucleophiles
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Anodic peak potentials for 42 anionic nucleophiles are reported along with the rate constants for the reactions of the anions with benzyl chloride.By comparing these rate constants with those of the reactions of outer-sphere electron-transfer reagents (radical anions), it has been demonstrated that the reactions of the anions with benzyl chloride are typical single-step SN2 reactions as opposed to a two-step process comprising dissociative single electron transfer (SET) to benzyl chloride followed by radical combination.The data suggest that very electron-rich nucleophilic anions with potentials of -1.5 to -2.2 V (and more negative) with respect to the ferrocenium/ferrocene couple might participate in a SET reaction.The 42 anions studied included representatives of four classes of nucleophiles, viz. sulfur-, carbon-, oxygen- and nitrogen-centred anions.The previously observed correlation of rate constants and anodic peak potential was again found for these anions with the most reactive species having the most negative peak potentials.Correlations by class indicate that the sensitivity of rate constants to changes in peak potential is greatest (and equivalent) for the sulfur-, carbon- and oxygen-anions and for representatives with the same peak potential, the rate constants by class follow the order sulfur > carbon > oxygen.The nitrogen nucleophiles show a significantly lower sensitivity of rate constant to changes in peak potential than do the other three classes.
- Niyazymbetov, Murat E.,Rongfeng, Zhou,Evans, Dennis H.
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p. 1957 - 1962
(2007/10/03)
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- THE NON-CHAIN RADICALOID C-ALKYLATION OF NITRONATE ANIONS: FURTHER EVIDENCE FOR THE MECHANISM
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The effects of the variation of solvent, pyridinium leaving group, N-substituent, and nitronate nucleophile have been studied in the C-alkylation of nitronate anions.These variations and studies of the effects of inhibitors, attempted entrainment reactions, and ESR work are all in accord with our previously suggested mechanism.
- Katritzky, Alan R.,Chen, Jen-Luan,Marson, Charles M.,Maia, Angalamaria,Kashmiri, M. Akram
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p. 101 - 108
(2007/10/02)
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- THE C-ALKYLATION OF NITROALKANE ANIONS BY 1-SUBSTITUTED-2-T-BUTYL-4-PHENYL- AND -2,4-DIPHENYL-5,6-DIHYDROBENZOQUINOLINIUM CATIONS.
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The N-substituents are transferred from the title cations to the C-atom of nitroalkane anions in high yield at 25-80 deg C in DMSO solution.The title cations are readily available from the appropriate pyrylium cations and primary amines of types RCH2NH2 and RR'CHNH2, allowing a general 2-step method for the preparation of higher nitroalkanes.Spectral properties of a variety of nitroalkanes are discussed.
- Katritzky, Alan R.,Kashmiri, M. Akram,Wittmann, Dieter K.
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p. 1501 - 1510
(2007/10/02)
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- Kinetics and Mechanism of the C-Alkylation of Nitroalkane Anions by 1-Alkyl-2,4,6-triphenylpyridiniums: A Nonchain Reaction with Radicaloid Characteristics
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The C-alkylation of 2-nitropropanide by N-substituted pyridiniums is first order in each reactant in Me2SO.The effect on the rate of temperature , N substituent, leaving group, and nucleophile was studied quantitatively.Overall, the evidence excludes an SN2 displacement and suggests that the reactions proceed by a free radical nonchain mechanism.
- Katritzky, Alan R.,Kashmiri, M. Akram,Ville, George Z. de,Patel, Ranjan C.
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- 2- and 4-(α-Substituted Aryl)pyridines as Leaving Groups in SN2 Reactions and Radicaloid Nucleophilic Displacements.
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Compared with 2,4,6-triphenylpyridine, 2,6-diphenyl-4-(o-substituted phenyl)pyridines as leaving groups in the radicaloid nucleophilic displacement reaction with 2-nitropropanide anion slow down C.T.C. formation. o-Substitution of the 2-phenyl group has little effect on this reaction.The latter modification however decreases SN2 rates of the corresponding pyridiniums with piperidine.
- Katritzky, Alan R.,Elisseou, E. Michael,Bashiardes, George,Patel, Ranjan C.
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p. 301 - 320
(2007/10/02)
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- NUCLEOPHILIC SUBSTITUTION IN ORGANOMERCURY HALIDES BY A FREE RADICAL CHAIN PROCESS
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Primary and secondary alkylmercury halides react with the salts of secondary nitroalkanes to afford tertiary nitroalkanes, mercury metal, and halide ion.The reaction is light initiated and is strongly inhibited by radical scavengers.Cyclized products resu
- Russel, Glen A.,Hershberger, James,Owens, Karen
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- THE SRN2 MECHANISM OF NUCLEOPHILIC SUBSTITUTION
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1-Alkylpyridiniums react with nitroalkane and ethylmalonate anions by a radical nucleophilic substitution mechanism not involving radical chains.
- Katritzky, Alan R.,Ville, George Z. de,Patel, Ranjan C.
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p. 1723 - 1726
(2007/10/02)
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