- SmI2(H2O)n Reduction of Electron Rich Enamines by Proton-Coupled Electron Transfer
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Samarium diiodide in the presence of water and THF (SmI2(H2O)n) has in recent years become a versatile and useful reagent, mainly for reducing carbonyl-type substrates. This work reports the reduction of several enamines by SmI2(H2O)n. Mechanistic experiments implicate a concerted proton-coupled electron transfer (PCET) pathway, based on various pieces of evidence against initial outer-sphere electron transfer, proton transfer, or substrate coordination. A thermochemical analysis indicates that the C-H bond formed in the rate-determining step has a bond dissociation free energy (BDFE) of ~32 kcal mol-1. The O-H BDFE of the samarium aquo ion is estimated to be 26 kcal mol-1, which is among the weakest known X-H bonds of stable reagents. Thus, SmI2(H2O)n should be able to form very weak C-H bonds. The reduction of these highly electron rich substrates by SmI2(H2O)n shows that this reagent is a very strong hydrogen atom donor as well as an outer-sphere reductant.
- Kolmar, Scott S.,Mayer, James M.
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supporting information
p. 10687 - 10692
(2017/08/15)
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- Cu-Catalyzed electrophilic amination of internal alkynes via hydroalumination
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A straightforward and efficient method for the synthesis of 1,2-diaryl-substituted enamines through the Cu-catalyzed electrophilic amination reaction of O-benzoyl hydroxylamines with vinylaluminum reagents generated in situ from the Ni-catalyzed hydroalumination of readily accessible internal aryl acetylenes is described. The amination is catalyzed by 1 mol% CuCl without any additive at ambient temperature to afford new versatile enamines in good yield (61-91%) with high selectivity (>98% E-enamine).
- Yoon, Hongju,Kim, Yuna,Lee, Yunmi
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supporting information
p. 790 - 795
(2017/02/05)
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- 1,3-Dipolar cycloaddition reactivities of perfluorinated aryl azides with enamines and strained dipolarophiles
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The reactivities of enamines and predistorted (strained) dipolarophiles toward perfluoroaryl azides (PFAAs) were explored experimentally and computationally. Kinetic analyses indicate that PFAAs undergo (3 + 2) cycloadditions with enamines up to 4 orders of magnitude faster than phenyl azide reacts with these dipolarophiles. DFT calculations were used to identify the origin of this rate acceleration. Orbital interactions between the cycloaddends are larger due to the relatively low-lying LUMO of PFAAs. The triazolines resulting from PFAA-enamine cycloadditions rearrange to amidines at room temperature, while (3 + 2) cycloadditions of enamines and phenyl azide yield stable, isolable triazolines. The 1,3-dipolar cycloadditions of norbornene and DIBAC also show increased reactivity toward PFAAs over phenyl azide but are slower than enamine-azide cycloadditions.
- Xie, Sheng,Lopez, Steven A.,Ramstr?m, Olof,Yan, Mingdi,Houk
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supporting information
p. 2958 - 2966
(2015/03/18)
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- Visible light-induced intermolecular radical addition: Facile access to γ-ketoesters from alkyl-bromocarboxylates and enamines
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A highly efficient addition of alkyl α-bromocarboxylates to enamines by visible light-induced photoredox catalysis is reported. Compared with traditional methods, the reaction described here provided an alternative route for the construction of valuable γ-ketoesters in generally good yields.
- Hu, Bei,Chen, Haixia,Liu, Yan,Dong, Wuheng,Ren, Kai,Xie, Xiaomin,Xu, Hao,Zhang, Zhaoguo
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supporting information
p. 13547 - 13550
(2015/01/09)
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- New nucleophilic rearrangement in the mechanism of the three-component domino cyclisation affording fluoroalkylated (pyrrolo)quinazolines
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The following mechanism steps were verified for the three-component domino cyclisation affording (pyrrolo)quinazolines from 2-(aminomethyl)aniline, a very reactive oxo compound and "usual" oxo compound. The first step was a rapid reaction of very reactive oxo compound (trifluoropyruvate or hexafluoroacetone) with benzylic amino group to form hemiaminal, but not imine; the second step was the reaction of oxo compound with aromatic amino group to form imine (Schiff base) being in equilibrium with its enamine form; the third step was an intramolecular attack of the hemiaminal carbon by the enamine carbon followed by a new nucleophilic rearrangement to form tetrahydropyrimidine cycle; the forth step was closure of the lactam ring, if ester group was available as in trifluoropyruvate.2013 Elsevier B.V. All rights reserved.
- Paleta, Old?ich,Dolensky, Bohumil,Pale?ek, Ji?í,Kví?ala, Jaroslav
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supporting information
p. 1 - 11
(2014/01/06)
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- New reaction of enamines with aryldiazoacetates catalyzed by transition metal complexes
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The reaction of aryldiazoacetates with enamines catalyzed by copper and rhodium complexes provided γ-keto esters in good yields. A full investigation of the effects of solvents, catalysts, enamines and aryldiazoacetates on the reaction was carried out. Careful analysis of the crude reaction mixture revealed a substituted enamine as the primary product, which was hydrolyzed over silica gel to give a γ-keto ester as the final product. A reaction mechanism involving nucleophilic addition of an enamine to a metal carbene and subsequent hydrogen transfer was proposed. Chiral dirhodium and copper catalysts were examined and found to provide γ-keto esters with no enantioselectivity. The result could be rationalized based on the proposed reaction mechanism. Attempts to trap the enamine intermediate with several electrophilic reagents were not successful.
- Zhao, Wei-Jie,Yan, Ming,Huang, Dan,Ji, Shun-Jun
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p. 5585 - 5593
(2007/10/03)
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- A highly effective catalyst system for the Pd-catalyzed amination of vinyl bromides and chlorides
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(Chemical Equation Presented) A highly efficient synthesis of enamines and imines by Pd-catalyzed amination of vinyl bromides or chlorides with amines is described using the Pd2(dba)3/P(i-BuNCH2CH 2)3N catalyst system.
- Reddy, Chinta Reddy Venkat,Urgaonkar, Sameer,Verkade, John G.
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p. 4427 - 4430
(2007/10/03)
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- Novel and convenient aldolization of methyl 3,3,3-trifluoropyruvate using enamines instead of ketones
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Piperidine enamines derived from acetone, acetophenone, cyclopentanone and cyclohexanone react easily in minutes with methyl 3,3,3-trifluoropyruvate (1) to afford products of the aldol condensation in high yields at room temperature, which is in contrast to the direct aldolization of 1 with the ketones.
- Palecek, Jiri,Paleta, Oldrich
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p. 521 - 524
(2007/10/03)
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- ZUR UMSETZUNG VON ARYLMETHYLKETONEN MIT SCHWEFEL, SEKUNDAEREN AMINEN UND SCHWEFELDIOXID
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The acetophenones 2 react with different sulfurdioxide-secondary amine adducts 1 and sulfur to yield the red-coloured zwitterionic 2-imino-dithioacetates 3.Enamines can be proved to be intermediates in this reaction.Thus enamines 5 and other derivatives such as acetophenone anil, acetophenone diethyl acetal and diphenacyl sulfide also give 3.In the absence of 1, 3a react with hydrogen sulfide to form the thioamide of phenylacetic acid 8. Key words: 2-Iminio-dithioacetates; iminium salts; zwitterionic; SO2-secondary amin adducts; Willgerodt-Kindler-reaction; enamines; heptathiocanes.
- Matschiner, Hermann,Maschmeier, Claus-Peter,Maier, Nadja,Hansen, Jens
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p. 223 - 230
(2007/10/02)
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- A Novel Deselenation in the Reaction of Selenoamides with Organolithium Reagents
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The reaction of selenoamides with organolithium reagents proceeds in a carbophilic manner, and more interestingly, the presence of excess lithium reagents causes a novel deselenation reaction from the carbophilic adducts.
- Sekiguchi, Masahito,Ogawa, Akiya,Fujiwara, Shin-Ichi,Ryu, Ilhyong,Kambe, Nobuaki,Sonoda, Noboru
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p. 2053 - 2056
(2007/10/02)
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- Carbonyl Methylenation Using a Titanium- Aluminum (Tebbe) Complex
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The titanium-aluminum (Tebbe) complex is shown to be an effective methylenating agent for a variety of carbonyl groups.The reaction is unique in that the carbonyl groups of carboxylic acid derivatives are readily methylenated.Thus vinyl enol ethers are prepared from esters and enamines are formed from amides.The complex provides a method for methylenating hindered or base sensitive ketones that is advantageous to the Wittig reagent.Selective methylenation of dicarbonyl compounds is also accomplished.
- Pine, Stanley H.,Pettit, Robert J.,Geib, Gregory D.,Cruz, Susana G.,Gallego, Claudio H.,et al.
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p. 1212 - 1216
(2007/10/02)
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