- Alkyl Halides via Visible Light Mediated Dehalogenation
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Net selective bromination and chlorination of activated C-H bonds can be effected in generally high yield via a simple perhalogenation/dehalogenation sequence. The photochemical reductions require no photocatalyst, relying instead on the formation of an electron donor-acceptor complex of the substrate and reductant, or alternatively autophotocatalysis. Some reactions proceed despite any apparent photon absorption, serving as a cautionary tale for other photochemical reactions involving amines. Mechanistic experiments provide an explanation for this observation.
- Rathnayake, Manjula D.,Weaver, Jimmie D.
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supporting information
p. 9681 - 9687
(2019/11/28)
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- Mixed-ligand complexes of paddlewheel dinuclear molybdenum as hydrodehalogenation catalysts for polyhaloalkanes
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We developed a hydrodehalogenation reaction of polyhaloalkanes catalyzed by paddlewheel dimolybdenum complexes in combination with 1-methyl-3,6-bis(trimethylsilyl)-1,4-cyclohexadiene (MBTCD) as a non-toxic H-atom source as well as a salt-free reductant. A mixed-ligated dimolybdenum complex Mo2(OAc)2[CH(NAr)2]2 (3a, Ar = 4-MeOC6H4) having two acetates and two amidinates exhibited high catalytic activity in the presence of nBu4NCl, in which [nBu4N]2[Mo2{CH(NAr)2}2Cl4] (9a), derived by treating 3a with ClSiMe3 and nBu4NCl, was generated as a catalytically-active species in the hydrodehalogenation. All reaction processes, oxidation and reduction of the dimolybdenum complex, were clarified by control experiments, and the oxidized product, [nBu4N][Mo2{CH(NAr)2}2Cl4] (10a), was characterized by EPR and X-ray diffraction studies. Kinetic analysis of the hydrodehalogenation reaction as well as a deuterium-labelling experiment using MBTCD-d8 suggested that the H-abstraction was the rate-determining step for the catalytic reaction. This journal is
- Tsurugi, Hayato,Hayakawa, Akio,Kando, Shun,Sugino, Yoshitaka,Mashima, Kazushi
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p. 3434 - 3439
(2015/05/27)
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- Efficient partial hydrogenation of trichloromethyl to gem-dichloromethyl groups in platinum on carbon-catalyzed system
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While gem-dichloromethyl groups can be directly synthesized by the mono-dechlorination of the corresponding trichloromethyl groups, the suppression control of the over-reduction to form chloromethyl or methyl functionalities is quite difficult. We have established the efficient and widely applicable mono-dechlorination method of the trichloromethyl groups to form the corresponding gem-dichloromethyl groups using platinum on carbon in dimethylacetamide as a specific solvent at 25 °C under a hydrogen atmosphere. The mono-dechlorination of the α,α,α- trichloromethylcarbonyl groups smoothly proceeded by the use of platinum on carbon as a catalyst in a highly chemoselective manner, while the efficient mono-dechlorination of the alkyl- and aryl-trichloromethyl groups required the combined use of Bu3SnH.
- Sawama, Yoshinari,Imanishi, Takahiro,Nakatani, Ryosuke,Fujiwara, Yuta,Monguchi, Yasunari,Sajiki, Hironao
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supporting information
p. 4540 - 4546
(2014/06/10)
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- SNAAP sulfonimidate alkylating agent for acids, alcohols, and phenols 1
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Stable, crystalline ethyl N-tert-butyl-4-nitrobenzenesulfonimidate has been prepared in high yield by direct O-ethylation of N-tert-butyl-4- nitrobenzenesulfonamide with iodoethane and silver(I) oxide in dichloromethane. This sulfonimidate directly ethylates various acids to esters; the stronger the acid, the faster it alkylates and in higher yield. It readily ethylates alcohols and phenols to ethers at room temperature in the presence of tetrafluoroboric acid catalyst without molecular rearrangements or racemization. We have defined these reactions as SNAAP alkylations: [substitution, nucleophilic of acids, alcohols and phenols]. The hard sulfonimidate alkylating agent is chemoselective, preferring oxygen > nitrogen > sulfur. The sulfonamide byproduct of alkylation is readily recycled to the sulfonimidate. Georg Thieme Verlag Stuttgart . New York.
- Maricich, Tom J.,Allan, Matthew J.,Kislin, Brett S.,Chen, Andrea I-T.,Meng, Fan-Chun,Bradford, Christine,Kuan, Nai-Chia,Wood, Jeremy,Aisagbonhi, Omonigho,Poste, Alethea,Wride, Dustin,Kim, Sylvia,Santos, Therese,Fimbres, Michael,Choi, Dianne,Elia, Haydi,Kaladjian, Joseph,Abou-Zahr, Ali,Mejia, Arturo
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p. 3361 - 3368
(2014/01/06)
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- Platinum on carbon-catalyzed precise reduction control of trichloromethyl to Geminal-dichloromethyl groups
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Geminal-dichloromethyl derivatives could be efficiently synthesized by the highly chemoselective platinum on carbon-catalyzed mono-dechlorination of trichloromethyl substrates in dimethylacetamide (DMA) as a specific solvent at 25 °C under a hydrogen atmosphere. Copyright
- Imanishi, Takahiro,Fujiwara, Yuta,Sawama, Yoshinari,Monguchi, Yasunari,Sajiki, Hironao
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supporting information; experimental part
p. 771 - 776
(2012/06/30)
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- Reactions of α-chloro β-oxo aldehydes with CH-acid anions
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The reactions of α-chloro and α,α-dichloro β-oxo aldehydes with carbanions are accompanied by the cleavage of the carbon-carbon bond in the chloro aldehydes and result in formylation of CH-acids. These electrophiles react with carbanions, which are generated in situ from CH-acids in the presence of AcONa in aprotic solvents, to form polyfunctional hydroxy compounds.
- Guseinov, F. I.
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p. 743 - 745
(2007/10/03)
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- Kinetics and mechanism of oxidation of aliphatic acetals with peroxomonosulphate
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The oxidation of fifteen aliphatic acetals of normal aliphatic aldehydes and substituted aliphatic aldehydes with aliphatic and substituted aliphatic as well as with aromatic alcohols by peroxomonosulphate in aqueous acetic acid medium is first order each in [oxidant] and [acetal] and yields the corresponding esters as the main product. The oxidation reaction is independent of change in dielectric constant of the medium. The activation enthalpies and entropies of the reactions are linearly related. A mechanism involving hydride ion shift is proposed.
- Janakiram,Venkataraman,Basheer Ahamed
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p. 339 - 341
(2007/10/03)
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- Kinetics and mechanism of oxidation of aliphatic acetals with N-chlorobenzamide
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The oxidation kinetics of thirteen aliphatic acetals of normal aliphatic aldehydes and substituted aliphatic aldehydes with aliphatic and substituted aliphatic as well as with aromatic alcohols by N-chlorobenzamide (NCB) in aqueous acetic acid medium follows first order and zero order dependence in [NCB] and [acetal] respectively and yields the corresponding esters as the main product of oxidation. (H2OCl)+ has been postulated as the oxidizing species.
- Basheer Ahamed
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p. 222 - 224
(2007/10/03)
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- Reactions of α-Chloro-β-oxoaldehydes with Dialkyl Phosphites
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Sodium dialkyl phosphites react with α-chloro- and α,α-dichloro-β-oxoaldehydes exclusively at the aldehyde carbonyl group with rupture of the C-CHO bond. The primary products are corresponding α-chloro- and α,α-dichloroenolates and unstable phosphinoylformaldehydes; the latter decompose into dialkyl hydrogen phosphites and carbon monoxide. Condensation products of α-halo-β-oxoaldehydes with dialkyl hydrogen phosphites in the presence of sodium hydride undergo similar transformations.
- Guseinov,Burangulova,Moskva
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p. 1564 - 1567
(2007/10/03)
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- Reactions of α-Chloro- and α,α-dichloro-β-oxoaldehydes with Anionic Nucleophiles
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The reaction of α-chloro and α,α-dichloro-β-oxoaldehydes with anionic nucleophiles (NaOH, MeONa, PhONa, MeCOOK) proceeds mainly via haloform splitting with elimination of the formyl group; only with the most nucleophilic sodium methoxide, the reaction at the β-carbon atom partially occurs.The intermediate anions react with benzaldehyde to give difficulty accessible polyfunctional compounds.
- Guseinov, F. I.,Tagiev, S. Sh.,Moskva, V. V.
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- Kinetics and mechanism of oxidation of aliphatic acetals with lead (IV) acetate
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The oxidative cleavage of aliphatic acetals of normal aliphatic aldehydes and substituted aliphatic aldehydes with aliphatic as well as aromatic alcohols with lead tetra acetate in acetic acid, aqueous acetic acid and in acetic acid-benzene medium is first order each in and and yields the corresponding esters as the main product.The rate of oxidation depends upon the dielectric constant of the medium.Stoichiometric investigations with different acetals indicated a 1:1 stoichiometry.
- Ahamed, K. A. Basheer,Nambi, K.
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p. 1104 - 1106
(2007/10/03)
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- Process for the reaction of a low-molecular hydroxyl compound with a carboxylic acid halide
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In a process for reacting a low molecular weight hydroxy compound with a carboxylic acid halide, a small amount of the acid halide is introduced into the reaction vessel and the remainder of the acid halide and the hydroxy compound are added gradually in an approximately stoichiometric ratio. The hydrogen halide formed is thus prevented from dissolving in the reaction medium. The heat of reaction to be dissipated is negligible.
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- REACTIONS OF α-CHLORO- AND α,α-DICHLORO-β-CARBONYL-SUBSTITUTED ALDEHYDES WITH AMINES
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Depending on the nature of the substrate (the chlorodicarbonyl compound) and the nature of the nucleophilic reagent (the amine), the reaction of α-chloro- and α,α-dichloro-β-carbonyl-substituted aldehydes with amines takes place mainly in three directions i.e., with the formation of enamines or imines or with cleavage of the C-CHO bond of the aldehydes.
- Guseinov, F. I.,Klimentova, G. Yu.,Moskva, V. V.
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p. 530 - 533
(2007/10/02)
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- Electron Transfer in the Reactions of Organic Trichloromethyl Derivatives with Iron(II) Chloride
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Reduction of trichloromethyl derivatives RCCl3 with iron(II) chloride in acetonitrile, has been studied in order to examine the mechanism of the electron transfer (ET) process and the reactions of the radicals formed.Substrates 1-3 afforded different product compositions and the cause was identified as differences in the reactivity of radicals which is substantially of two types: reductive coupling and proton abstraction after further reduction to a carbanion coordinated to the metal ion.Compound 1 gave only coupling products, compound 2 only hydrogenated products and compound 3 a mixture of coupling and hydrogenated products depending on experimental conditions.Proton abstraction by the carbanion was found to occur from water molecules, which should be present in the coordination shell of the metal ion, and not from the solvent.The different behaviour of compounds 1-3 is attributed to the presence of substituents which are able to stabilize the radical and carbanionic intermediates.Rate constants at different temperatures were measured and the activation parameters calculated.The three substrates differ only slightly in reaction rates, in the order 1 > 2 > 3.Activation enthalpies are very close to each other and this agrees with the almost equal values of C-Cl bond dissociation energies of compounds 1-3, empirically determined.Large, negative entropies of activation were found, suggesting that an ordered activation complex should be formed in order that electron transfer from the metal ion to the organic halide can take place.
- Cornia, Andrea,Folli, Ugo,Sbardellati, Silvia,Taddei, Ferdinando
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p. 1847 - 1854
(2007/10/02)
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- Fluoride anion catalyzed halogen dance in polyhalomethanes
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Tetrabutylammonium fluoride catalyzes the exchange of halogens between tetrahalomethanes.The presence of small amounts of haloform is suspected to be a necessary co-catalyst.Key Words: tetrabutyl ammonium fluoride; tetrahalomethanes; halogen exchange in.
- Sasson, Y.,Kitson, F.,Webster, O, W.
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p. 599 - 600
(2007/10/02)
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- ADDITION OF ESTERS OF CHLOROACETIC ACIDS TO 1,3-BUTADIENE CATALYSED BY COPPER COMPLEXES
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The addition of alkyl trichloro- and dichloroacetates to 1,3-butadiene catalysed by copper complexes has been studied.The reactivity of the chloroacetates increased with increasing number of chlorine atoms in their molecule and with decreasing number of the carbon atoms of the alkyl of their ester group.The addition of trichloroacetates gave the products (1 : 1 adducts) in around 80 per cent yields while the less reactive dichloroacetates afforded the adducts in 35percent yield.The 1 : 1 adducts were the products of both 1,4- and 1,2- addition, the relative proportion of which depended especially on the type of the ligand of copper complexes.
- Vit, Zdenek,Hajek, Milan
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p. 1280 - 1284
(2007/10/02)
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- TETRAHEDRAL INTERMEDIATES 4. THE EFFECT OF CHLORO-SUBSTITUENTS ON THE KINETICS OF THE BREAKDOWN OF HEMIORTHOESTERS
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2-Hydroxy-2-chloromethyl-1,3-dioxolane (4) and 2-hydroxy-2-dichloromethyl-1,3-dioxolane (5) have been detected as intermediates by 1H NMR spectroscopy in the hydration of respectively 2-chloromethylene-1,3-dioxolane and 2-dichloromethylene-1,3-dioxolane in aqueous acetonitrile.The kinetics of the breakdown of (4) and (5) into ethylene glycol monochloroacetate and monodichloroacetate have been studied by uv spectroscopy and values of kH(+), kHO(-), and kH2O evaluated.It was found that the introduction of chlorosubstituents into 2-hydroxy-2-methyl-1,3-dioxolane caused a decrease in kH(+) and increase in kHO(-) and little change in kH2O for its breakdown.The mechanisms of these reactions are discussed.
- Capon, Brian,Dosunmu, Miranda I.
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p. 3625 - 3634
(2007/10/02)
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- REACTIVITY OF CHLOROSUBSTITUTED α-EPOXIDES AND SYNTHESES UNDER THESE COMPOUNDS
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The reactivity of chloroepoxyethanes in reactions with nucleophiles and electrophiles increases sharply with the accumulation of chlorine atoms on the epoxide ring.The reaction rate correlates with the nucleophile strength.Reactions with strong nucleophiles proceed through epoxide isomerization and lead to chloroacetic acid derivatives.Addition to the epoxide ring is found only for several weak nucleophiles.
- Voronina, T. A.,Fomina, N. V.,Suminov, S. I.
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p. 1059 - 1063
(2007/10/02)
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- REACTIONS OF CHLORINE MONOFLUORIDE. IV. ADDITION OF CHLORINE MONOFLUORIDE TO HALOGEN-SUBSTITUTED ALKENES
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The reactions of chlorine monofluoride with halogenoethylenes (1,1-dichloro-, 1,2-dichloro-, trichloro-, and tetrachloroethylenes) and halogenopropenes ( 3-bromo-, 3,3,3-trichloro-, E- and Z-1,3-dichloro-, 3-chloro-2-methyl-, and perfluoropropenes) were investigated in inert solvents in the presence of ethyl acetate as external nucleophile.In all cases chloroacyloxy adducts were isolated and identified in addition to the chlorofluorination products, and this indicates an electrophilic mechanism for the chlorofluorination of polyhalogenoalkenes.Methyl chloromaleate, chlorofumarate, chlorofluoroethylenedicarboxylate, α,β-difluoroacrylate, and perfluoromethacrylate in anhydrous hydrogen fluoride form the corresponding chlorofluoro adducts with satisfactory yields, whereas the reaction takes place with difficulty in inert solvents.
- Boguslavskaya, L. S.,Chuvatkin, N. N.,Panteleeva, I. Yu.
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p. 1832 - 1842
(2007/10/02)
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