- Mechanistic Studies on the Michael Addition of Amines and Hydrazines to Nitrostyrenes: Nitroalkane Elimination via a Retro-aza-Henry-Type Process
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In this article we report on the mechanistic studies of the Michael addition of amines and hydrazines to nitrostyrenes. Under the present conditions, the corresponding N-alkyl/aryl substituted benzyl imines and N-methyl/phenyl substituted benzyl hydrazones were observed via a retro-aza-Henry-type process. By combining organic synthesis and characterization experiments with computational chemistry calculations, we reveal that this reaction proceeds via a protic solvent-mediated mechanism. Experiments in deuterated methanol CD3OD reveal the synthesis and isolation of the corresponding deuterated intermediated Michael adduct, results that support the proposed slovent-mediated pathway. From the synthetic point of view, the reaction occurs under mild, noncatalytic conditions and can be used as a useful platform to yield the biologically important N-methyl pyrazoles in a one-pot manner, simple starting with the corresponding nitrostyrenes and the methylhydrazine.
- Kallitsakis, Michael G.,Tancini, Peter D.,Dixit, Mudit,Mpourmpakis, Giannis,Lykakis, Ioannis N.
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p. 1176 - 1184
(2018/02/09)
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- Visible-Light Photoredox-Catalyzed C-H Difluoroalkylation of Hydrazones through an Aminyl Radical/Polar Mechanism
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An unprecedented visible-light-induced direct C-H bond difluoroalkylation of aldehyde-derived hydrazones was developed. This reaction represents a new way to synthesize substituted hydrazones. The salient features of this reaction include difluorinated hy
- Xu, Pan,Wang, Guoqiang,Zhu, Yuchen,Li, Weipeng,Cheng, Yixiang,Li, Shuhua,Zhu, Chengjian
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supporting information
p. 2939 - 2943
(2016/02/27)
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- Gold-Catalyzed Highly Selective Photoredox C(sp2)-H Difluoroalkylation and Perfluoroalkylation of Hydrazones
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The first gold-catalyzed photoredox C(sp2)-H difluoroalkylation and perfluoroalkylation of hydrazones with readily available RF-Br reagents is reported. The resulting gem-difluoromethylated and perfluoroalkylated hydrazones are highl
- Xie, Jin,Zhang, Tuo,Chen, Fei,Mehrkens, Nina,Rominger, Frank,Rudolph, Matthias,Hashmi, A. Stephen K.
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supporting information
p. 2934 - 2938
(2016/02/27)
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- A Single Electron Transfer (SET) Approach to C-H Amidation of Hydrazones via Visible-Light Photoredox Catalysis
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The reductive single electron transfer (SET) umpolung amination of aldehyde-derived hydrazones has been developed through visible-light-promoted photoredox catalysis. The ideal transformation of hydrazones into the corresponding hydrazonamide through selective carbon-hydrogen (C-H) bond functionalization represents one of the most step- and atom-economical methods. This SET umpolung strategy features mild conditions and a remarkably broad substrate scope, offering an entirely new substrate class to direct C-H amination.
- Zhang, Muliang,Duan, Yingqian,Li, Weipeng,Xu, Pan,Cheng, Jian,Yu, Shouyun,Zhu, Chengjian
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supporting information
p. 5356 - 5359
(2016/11/02)
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- New types of reactivity of α,β-unsaturated N,N- dimethylhydrazones: Chemodivergent diastereoselective synthesis of functionalized tetrahydroquinolines and hexahydropyrrolo[3,2-b]indoles
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The indium trichloride-catalyzed reaction between aromatic imines and α,β-unsaturated N,N-dimethylhydrazones in acetonitrile afforded 1,2,3,4-tetrahydroquinolines bearing a hydrazone function at C4 through a one-pot diastereoselective domino process that involves the formation of two C-C bonds and the controlled generation of two stereocenters, one of which is quaternary. This reaction constitutes the first example of an α,β-unsaturated dimethylhydrazone that behaves as a dienophile in a hetero Diels-Alder reaction. The related reaction between anilines, aromatic aldehydes, and methacrolein dimethylhydrazone in CHCl3 with BF 3·Et2O as catalyst afforded polysubstituted 1,2,3,3a,4,8b-hexahydropyrrolo[3,2-b]indoles as major products through a fully diastereoselective ABB′C four-component domino process that generates two cycles, three stereocenters, two C-C bonds, and two C-N bonds in a single operation. Copyright
- Sridharan, Vellaisamy,Ribelles, Pascual,Estevez, Veronica,Villacampa, Mercedes,Ramos, M. Teresa,Perumal, Paramasivan T.,Menendez, J. Carlos
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p. 5056 - 5063
(2012/05/20)
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- Reaction of the lithio-derivative of methoxyallene with hydrazones. Part 1: Synthesis and transformation of α-allenyl hydrazines
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The lithio-derivative of methoxyallene reacts with aldehyde hydrazones leading to expected α-allenyl hydrazines when ether is the solvent of the reaction. The yields are good as well as the diastereoselectivity observed in the case of SAMP-hydrazones. These hydrazines are cleanly transformed to N-dialkylamino-3-methoxy-3-pyrrolines when they are reacted with n-BuLi in THF. These compounds are sometimes accompanied by the isomeric 4-methyl azetidines. The N-dialkylamino-3-methoxy-3-pyrrolines are transformed to 3-methoxy-3-pyrrolines by hydrogenolysis of the nitrogen-nitrogen bond, to 3-alkoxy-pyrroles by treatment with a peracid and to 3-amino-pyrroles by acidic migration of the dialkylamino group. In the case of SAMP-hydrazines, the obtained 3-methoxy-3-pyrrolines have a high enantiomeric purity. Lastly, attempts to prepare α-hydrazino-esters (and subsequently α-amino-esters) by ozonolysis of the allenyl moiety failed due to the formation of a methyl glyoxylate.
- Breuil-Desvergnes, Valérie,Goré, Jacques
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p. 1939 - 1950
(2007/10/03)
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- A facile synthesis of 3-alkoxy and 3-amino pyrroles
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N-Amino-3-methoxy-3-pyrrolines 2 obtained from the reaction of 1-lithio methoxyallene with arylhydrazones may be converted to either 3-methoxy pyrroles 6 or 3-amino pyrroles 7 by treatment with m-chloroperbenzoic acid or 0.25 M HCl, respectively.
- Breuil-Desvergnes, Valerie,Compain, Philippe,Vatele, Jean-Michel,Gore, Jacques
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p. 8789 - 8792
(2007/10/03)
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- Elimination Reactions of Hydrazonium Salts: Experimental and Theoretical Evidence for a Large Stereoelectronic Effect of Nitrogen
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Elimination of trimethylamine from hydrazonium salts (8, R = Me) is promoted by base (methoxide ion in methanol).The mechanism is characterized as E2 as shown by substituent effects (ρ = +2.57), Broensted coefficients, a primary kinetic isotope effect (kH/kD = 2.10), and solvent effects.Variation in the leaving group (8, R = arylmethyl) shows that N-N bond cleavage is less well advanced in the transition state than C-H bond breaking.The elimination to give the nitrile is syn-periplanar and, using the phthalazinium salt 4 as a model for the anti elimination, an anti/syn ratio of ca. 102 is found.The reactions have been modelled using ab initio methods with the transition structures located at the HF/3-21G level and relative energies computed using the MP2/6-31G* method.Using both H2O and NH3 as model bases to induce elimination on +, the calculated energy for anti elimination is lower (in the range 11-13 kcal mol-1) than that for syn elimination.The implications of the results for the ease of formation of nitriles from aldehydes via the hydrazonium salt route are discussed.
- Nguyen, Minh Tho,Clarke, Leo F.,Hegarty, Anthony F.
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p. 6177 - 6183
(2007/10/02)
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