- A practical synthetic method for vinyl chlorides and vinyl bromides from ketones via the corresponding vinyl phosphate intermediates
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A new synthetic method for the preparation of vinyl chlorides and vinyl bromides from acyclic and cyclic ketones is described. Vinyl halides are practically obtained from the corresponding vinyl phosphate intermediates with triphenylphosphine dihalide.
- Kamei, Katsuhide,Maeda, Noriko,Tatsuoka, Toshio
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Read Online
- A novel titanium tetrahalide-mediated carbon-carbon bond-forming reaction: Regioselective synthesis of substituted (E,Z)-1,5-dihalo-1,4-dienes
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(matrix presented) Reactions of aldehydes with 2 equiv of alkyne in the presence of TiX4 (X = Cl, Br) regioselectively generated 1,5-dihalo-1,4-dienes in moderate to good yields with high (E,Z)-stereoselectivity.
- Kabalka, George W.,Wu, Zhongzhi,Ju, Yuhong
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Read Online
- Synthesis of Unsymmetrical 1,4-Dicarbonyl Compounds by Photocatalytic Oxidative Radical Additions
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Herein we report a photocatalytic oxidative radical addition reaction for the synthesis of unsymmetrical 1,4-dicarbonyl compounds. This reaction utilizes a desulfurization process to generate electrophilic radicals, which add to α-halogenated alkenes and undergo further oxidation to deliver 1,4-dicarbonyl compounds. This mild and highly efficient method provides a valuable alternative to known strategies.
- Dong, Ya,Li, Ruining,Zhou, Junliang,Sun, Zhankui
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supporting information
p. 6387 - 6390
(2021/08/23)
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- Method for preparing vinyl chloride compound by utilizing phosgene
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The invention relates to a method for preparing a vinyl chloride compound by using phosgene. The method comprises the following steps: dropwise adding an organic solvent solution of phosgene into an organic solvent solution containing quaternary phosphoni
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Paragraph 0097-0109
(2020/06/20)
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- A Chlorinating Reagent Yields Vinyl Chlorides with High Regioselectivity under Heterogeneous Gold Catalysis
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A novel chlorinating reagent with a high concentration of HCl has enabled the highly regioselective hydrochlorination of unactivated alkynes using a commercial nanogold catalyst. No overchlorination or hydration products were formed, and various functional groups were tolerated. This hydrochlorination method could be conducted under open air.
- Liang, Shengzong,Ebule, Rene,Hammond, Gerald B.,Xu, Bo
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supporting information
p. 4524 - 4527
(2017/09/11)
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- Chloride-tolerant gold(I)-catalyzed regioselective hydrochlorination of alkynes
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We have developed a highly regioselective homogeneous gold(I)-catalyzed anti-hydrochlorination of unactivated alkynes at room temperature. We have overcome the incompatibility between conventional cationic gold catalysts and chloride by using a hydrogen-b
- Ebule, Rene,Liang, Shengzong,Hammond, Gerald B.,Xu, Bo
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p. 6798 - 6801
(2017/11/09)
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- Catalyst-free hydrochlorination protocol for terminal arylalkynes with hydrogen chloride
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We present a simple and straightforward protocol for hydrochlorination of terminal arylalkynes to vinyl chlorides using hydrogen chloride under mild reaction conditions. This protocol does not involve any metal catalysts or additives. It is simple, inexpensive, and easy to prepare, and exhibits good reaction activity. The hydrochlorination proceeds smoothly to yield unique regioselective products via the Markovnikov addition rule.
- Xu, Cai-Xia,Ma, Cun-Hua,Xiao, Fu-Rong,Chen, Hong-Wei,Dai, Bin
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supporting information
p. 1683 - 1685
(2016/11/12)
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- Catalytic Enantioselective Synthesis of Halocyclopropanes
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A catalytic asymmetric synthesis of halocyclopropanes is described. The developed method is based on a carbenoid cyclopropanation of 2-haloalkenes with tert-butyl α-cyano-α-diazoacetate using a chiral rhodium catalyst that permits access to a broad range
- Pons, Amandine,Ivashkin, Pavel,Poisson, Thomas,Charette, André B.,Pannecoucke, Xavier,Jubault, Philippe
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supporting information
p. 6239 - 6242
(2016/05/02)
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- Synthesis of Vinyl Chlorides via Triphosgene-Pyridine Activation of Ketones
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Herein, we describe a mild method to prepare aliphatic and aromatic vinyl chlorides from their corresponding ketones via triphosgene-pyridine activation in dichloromethane at reflux. The mechanism of this reaction is proposed to involve formation of a put
- Saputra, Mirza A.,Ngo, Ly,Kartika, Rendy
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p. 8815 - 8820
(2015/09/15)
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- Selective Ruthenium-Catalyzed Hydrochlorination of Alkynes: One-Step Synthesis of Vinylchlorides
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An unprecedented ruthenium-catalyzed direct and selective alkyne hydrochlorination is reported and leads to vinylchlorides in excellent yields with atom economy. The reaction proceeds at room temperature from terminal alkynes and provides a variety of chloroalkenes. Only the regioisomer resulting from the formal Markovnikov addition is selectively formed. Mechanistic studies show the stereoselective syn addition of HCl to alkynes at room temperature and suggest a chloro hydrido RuIV species as a key intermediate of the reaction.
- Dérien, Sylvie,Klein, Hubert,Bruneau, Christian
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supporting information
p. 12112 - 12115
(2015/10/12)
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- Hydration of aromatic terminal alkynes catalyzed by iron(III) sulfate hydrate under chlorine-free conditions
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The hydration of aromatic terminal alkynes performed in acetic acid in the presence of catalytic hydrate ironIII sulfate, Fe2(SO 4)3·nH2O (4-9 mol %), yields the derived aryl methyl ketones with good to excellent yields. Under comparable conditions (18 mol %, 95 C, 24 h), bifunctional substrates were transformed into the monoacetyl or the diacetyl derivatives, depending on the structure of the aromatic diyne. The reaction is compatible with aryl substituents of different nature and ring positions, including hydroxyl, carbonyl groups, and cumulated hydrocarbons. The soft character of the non nucleophilic sulfate anion allows for activation of the triple bond toward carbonoxygen bond formation in the Br?nsted acidic medium. The proposed protocol is based on readily available and non toxic materials, in the absence of chlorine atoms in either the solvent or the metal catalyst.
- Bassetti, Mauro,Ciceri, Samuele,Lancia, Federico,Pasquini, Chiara
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supporting information
p. 1608 - 1612
(2014/03/21)
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- A mild synthesis of vinyl halides and gem-dihalides using triphenyl phosphite-halogen-based reagents
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A new application of (PhO)3P-halogen-based reagents to the synthesis of vinyl halides and gem-dihalides is described. Vinyl halides were prepared in good to excellent yields from enolizable ketones, whereas aldehydes afforded the corresponding gem-dihalides. The halogenation proceeded smoothly under mild conditions.
- Spaggiari, Alberto,Vaccari, Daniele,Davoli, Paolo,Torre, Giovanni,Prati, Fabio
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p. 2216 - 2219
(2007/10/03)
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- First catalytic and green synthesis of aryl-(Z)-vinyl chlorides and its plausible addition-elimination mechanism
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(Chemical Equation Presented) Via a catalytic cycle in the presence of scandium triflate (2 mol %)/DMF (1 mol %)/benzoyl chloride (5 mol %), aromatic ketones were treated with bis(trichloromethyl) carbonate (BTC) to afford aryl-(Z)-vinyl chlorides. All metal triflates tested in the reaction showed highly catalytic activity. A plausible addition-elimination mechanism was proposed. The present work describes the first catalytic and green route to the synthesis of aryl-(Z)-vinyl chlorides.
- Su, Weike,Jin, Can
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p. 993 - 996
(2007/10/03)
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- Conformationally restricted aza-BODIPY: Highly fluorescent, stable near-infrared absorbing dyes
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Novel NIR fluorescent, conformational restricted aza-dipyrromethene boron difluoride (aza-BODIPY) dyes were prepared by an efficient process. Such conformational restricted aza-BODIPY dyes possess intense absorption, strong fluorescence, high chemical and
- Zhao, Weili,Carreira, Erick M.
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p. 7254 - 7263
(2007/10/03)
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- One-step synthesis of aromatic terminal alkynes from their corresponding ketones under microwave irradiation
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One-step microwave-assisted synthesis of phenylacetylenes 2a-j from the corresponding ketones 1a-j in the presence of a new reagent, PCl 5 -pyridine, is described. The reaction is carried out under a simple operational and experimental procedure, avoiding the use of the complicated and harsh multistep reaction. Copyright Taylor & Francis Group, LLC.
- Ghaffarzadeh, Mohammad,Bolourtchian, Mohammad,Fard, Zohreh,Halvagar, Mohammad,Mohsenzadeh, Farshid
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p. 1973 - 1981
(2007/10/03)
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- Mechanism of dehydrobromination of 1,2-dibromo-1-phenylethane under conditions of phase-transfer catalysis
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Selective dehydrobromination of 1,2-dibromo-1-phenylethane to α-bromostyrene was effected under conditions of phase-transfer catalysis in systems containing KOH, toluene, and tetraalkylammonium bromides. The high selectivity of the catalytic systems originates from stabilization by lipophilic cation of the phase-transfer catalyst of a E1cb-like transition state in the E2 mechanism. In the presence of a catalytic amount of lipophilic alcohols, phenylacetylene was obtained. Substrate activation by alcohol molecules is explained by enhancement of the acceptor power of halogen atoms due to solvation and by increased mobility of hydrogen atoms.
- Suvorova,Panicheva,Mamontova,Belyatskii
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p. 957 - 962
(2007/10/03)
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- Method for chlorinating ketones
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In a process for chlorinating ketones which, apart from the carbonyl group, are inert in respect of triarylphosphine dichlorides, except for cyclopropyl methyl ketone, in which the ketones are reacted with a chlorinating agent in the presence of triarylphosphine oxides, the amount of triarylphosphine oxide is from 0.1 to 10 mol %, based on the amount of ketone. The ketones preferably have a least one CH-acid proton in the α position to the carbonyl group.
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- Reaction of phenylenedioxytrihalogenophosphoranes with arylacetylenes. Synthesis and spatial structure of the derivatives of 2-oxo-4-aryl-5,6-benzo-1,2-oxaphosphorin-2-enes
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New method of synthesis of six-membered heterocycles - 2-R-2-oxo-4-aryl-2H-benzo[e][1,2]-oxaphosphorin-3-enes has been developed. It includes the interaction of arylenedioxy trihalogenophosphoranes with arylacetylenes. The formation of phosphoryl group and P-C bond, ipso-substitution of the aromatic oxygen and halogenation of the benzene ring take place in this unusual reaction. The influence of the phosphorane structure on synthetic result is discussed. If both para positions at benzene ring of the phosphorane are occupated by halogens, the evolving of halogen molecule occurs. The structures of 2-R-2-oxo-4-aryl-2H-benzo[e][1,2]-oxaphosphorin-3-enes are determined by X-ray analysis.
- Mironov, Vladimir F.,Gubaidullin, Aidar T.,Petrov, Ravil R.,Litvinov, Igor A.,Shtyrlina, Alfiya A.,Zyablikova, Tatyana A.,Azancheev, Nail M.,Konovalov, Alexander I.,Musin, Rashid Z.
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p. 377 - 380
(2007/10/03)
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- A new method for the one-step conversion of oximes into gem-halo-nitro derivatives
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A mild and efficient process for one-step conversion of oximes into gem- halo-nitro compounds using Oxone and sodium chloride or potassium bromide is described.
- Curini, Massimo,Epifano, Francesco,Marcotullio, Maria Carla,Rosati, Ornelio,Rossi, Monia
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p. 6211 - 6218
(2007/10/03)
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- Direct preparation of vinyl halides from the corresponding ketones and acetyl halides
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Vinyl chlorides and bromides are obtained in good yield from the corresponding ketones and acetyl halides in the presence of trifluoroacetic or trifluoromethanesulfonic acid. The Z isomer is selectively formed.
- Moughamir, Khadija,Mezgueldi, Bouchra,Atmani, Aziz,Mestdagh, Helene,Rolando, Christian
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- Reactions of Phenylenedioxytrihalophosphoranes with Arylacetylenes: I. Synthesis and Steric Structure of 2H-Benzo[e][1,2]oxaphosphorin-3-ene Derivatives
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Reactions of phenylenedioxytrihalophosphoranes with arylacetylenes yield 2-halo-4-aryl-2H-benzo[e][1,2]oxaphosphorin-3-ene 2-oxides. Formation of the P-C bond and phosphoryl group is accompanied by ipso substitution of the oxygen atom in the benzodioxaphospholane fragment and halogenation of this fragment at the position para relative to the remaining oxygen atom.
- Mironov,Konovalov,Litvinov,Gubaidullin,Petrov,Shtyrlina,Zyablikova,Musin,Azancheev,Il'yasov
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p. 1414 - 1442
(2007/10/03)
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- Benzylchlorocarbene: Origins of Arrhenius Curvature in the Kinetics of the 1,2-H Shift Rearrangement
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Benzylchlorocarbene (1, BCC) was generated photochemically from benzylchlorodiazirine (2) in isooctane, methylcyclohexane (MCH), and tetrachloroethane (TCE) at temperatures from ~30 to -75°C. At -70°C in isooctane, the identified products included Z/E-β-chlorostyrenes 4 (46.6%), α-chlorostyrene 5 (2.4%), l,1-dichloro-2-phenylethane 6 (1.9%), a BCC-isooctane insertion product 8 (5.5%), carbene dimers 9 (3.8%), and azine 3 (30%). The significant incursion of intermolecular products 3, 8, and 9 implies that laser flash photolytic (LFP) kinetic data for the decay of BCC obtained at low temperature is biased and should not be employed in Arrhenius analyses. Accordingly, previously obtained curved Arrhenius correlations for BCC do not necessarily implicate , quantum mechanical tunneling (QMT) in the 1,2-H shift rearrangement of BCC to 4. Similarly in MCH, where BCC affords a solvent insertion product in ~44-53% yield, the curved Arrhenius correlation (Figure 1) cannot be readily interpreted. In polar solvents such as TCE, clean H-shift reactions of BCC are obtained even at -71°C; an Arrhenius correlation of LFP kinetic data is linear from 3 to -71°C (Figure 2), affording Ea = 3.2 kcal mol-1 and log A = 10.0 s-1. Therefore, QMT does not appear to play a major role in the 1,2-H shift rearrangement of BCC at ambient or near ambient temperature in solution.
- Merrer, Dina C.,Moss, Robert A.,Liu, Michael T.H.,Banks,Ingold, Keith U.
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p. 3010 - 3016
(2007/10/03)
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- Use of kinetic isotope effects in mechanism studies. Isotope effects and element effects associated with Hydron-Transfer steps during alkoxide-promoted dehydrohalogenations
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The Arrhenius behavior of the primary kinetic isotope effect, (k(H)/k(D))(Obs) and (k(H)/k(T))(Obs), associated with the methanolic sodium methoxide-promoted dehydrohalogenations of m-ClC6H4C(i)HClCH2Cl (I), m-CF3C6H4C(i)-HClCH2Cl (II) and p-CF3C6H4C(i)HClCH2F (III) has been used to calculate the internal-return parameters, a = k(-1)/K(Elim)(X), in a two-step mechanism featuring a hydrogen-bonded carbanion. This carbanion partitions between returning the hydron to carbon, k(-1), and the loss of halide, K(Elm)(X). Isotope effects at 25°C for I, (k(H)/k(D))(Obs) = 3.40 and (k(H)/ k(T))(Obs) = 6.20, and II, (k(H)/k(D))(Obs) = 3.49 and (k(H)/k(T))(Obs) = 6.55, result in similar values for a: a(H) = 0.59, a(D) = 0.13-0.14 and a(T) = 0.07. Smaller values of (k(H)/k(D))(Obs) = 2.19 and (k(H)/k(T))(Obs) = 3.56 for III are due to more internal return [a(H) = 1.9, a(D) = 0.50, and a(T) = 0.28] associated with the dehydrofluorination reaction. Calculation of k1 ( k(Obs) [a + 1]) results in similar isotope effects for hydron transfer in these reactions: k1(H)/k1(D) = 4.74 and k1(H)/K1(T) = 9.20; II, k1(H)/k1(D) = 4.91 and k1(H)/k1(T) = 9.75; III, k1(H)/k1(D) = 4.75 and k1(H)/k1(T) = 9.17. Reactions of m-ClC6H4C(i)HBrCH2Br and m-ClC6H4C(i)HClCH2Br have very small amounts of internal return, a(H) = 0.05 and a(D) = 0.01, and (k(H)/k(D))(Obs) = 4.95 results in k1(H)/k1(D) = 5.11 The measured isotope effects are therefore due to differences in the amount of internal return and not in the symmetry of transition state structures for the hydron transfer, and the element effect, (k(HBr)/ k(HCl)) = 29, for m-ClC6H4CHClCH2X is mainly due to the hydron-transfer step, k1(HBr)/k1(HCl) = 19, and not the breaking of the C-X bend. The kinetic solvent isotope effects, k(MeOD)/k(MeOH) ~ 2.5, are consistent with three methanols of solvation lost prior to the hydron-transfer step. The energetics associated with desolvation of methoxide ion are part of the measured reaction energetics of these systems.
- Koch, Heinz F.,Lodder, Gerrit,Koch, Judith G.,Bogdan, David J.,Brown, Geoffrey H.,Carlson, Carrie A.,Dean, Amy B.,Hage, Ronald,Han, Patrick,Hopman, Johan C. P.,James, Lisa A.,Knape, Petra M.,Roos, Eric C.,Sardina, Melissa L.,Sawyer, Rachael A.,Scott, Barbara O.,Testa III, Charles A.,Wickham, Steven D.
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p. 9965 - 9974
(2007/10/03)
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- FeCl3-H2O: A specific system for arylacetylene hydration
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FeCl3 has been found to be very specifically effective in the hydration of terminal aromatic alkynes to the corresponding methylketones.
- Damiano, Jean Pierre,Postel, Michele
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p. 303 - 305
(2007/10/03)
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- Flash Vacuum Thermolysis of Four Membered Rings Containing Nitrogen Atom. Part IV. Some Mechanistic Aspects of the Thermal Decomposition of Azetidines
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Thermal cycloreversions of substituted azetidine rings under FVT conditions have been studied.It was found that the regiochemistry of these reactions depends on the nature of substituents present in the system.The assumed 1,4-diradical stepwise mechanism enabled us to compare the competition in breaking of the first bond (N-C2 or C2-C3) depending on the stability of newly formed 1,4-diradical. - Keywords: azetidines, flash vacuum thermolysis
- Lesniak, S.
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p. 1484 - 1489
(2007/10/03)
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- Studies on the Oxidation of α-Substituted Styrenes. I. Reactivity and Formation of Reaction Products During the Oxidation of Styrene Derivatives
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The liquid phase oxidation of α-tert, -butyl, α-bromo-, α-chloro-, and α-methyl styrene with pure oxygen was investigated in a closed apparatus in chlorobenzene solution and in presence of cumene and of cumene hydroperoxide in the temperature range 35-125 deg C.The product yields were determined gaschromatographically.The difference of the activation energies of the epoxide formation and the parallel reactions were calculated.They amount to 27-38 kJ/mol.The epoxide selectivity increases with increasing temperature and decreases with increasing concentration of cumene.Relative chain propagation constants related to the tertriary CH-bond of cumene were determined from cooxidation experiments.
- Suprun, Wladimir,Blau, Karla,Reinker, Kathrin
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p. 496 - 503
(2007/10/02)
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- Flash Vacuum Thermolysis of Four Membered Rings Containing Nitrogen Atom. Part I. Thermal Decomposition of Azetidines
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The addition of acetic acid or hydrogen chloride followed by the nitrosation of azabicyclobutanes produced 1-nitroso-3-acetoxy-(or -chloro)azetidines.The thermal decomposition of these compounds under FVT conditions was studied.The cycloreversion of azetidine ring, entirely regioselective, was observed.Key words: azabicyclobutanes, azetidines, flash vacuum thermolysis
- Bartnik, R.,Lesniak, S.,Galindo, A.
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p. 719 - 726
(2007/10/02)
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- SYNTHESIS OF PYRIMIDINES FROM VINYL CHLORIDES AND NITRILES BY THE RITTER REACTION
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Chloroalkenes with a chlorine atom at the vinylic position and also phenylacetylene react with nitriles in the presence of trifluoromethanesulfonic acid to form tri- and tetrasubstituted pyrimidines.
- Borodaev, S. V.,Zubkova, O. V.,Luk'yanov, S. M.
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p. 2100 - 2103
(2007/10/02)
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- HYDROLYTIC SELENOXIDE ELIMINATION REACTION FOR THE PREPARATION OF 2-CHLORO-1-OLEFINS
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2-Chloro-1-olefins were synthesized in a regiocontrolled way from terminal olefins by a sequence involving Markownikoff-addition of PhSeCl, chlorination of the resulting β-chloroalkyl phenyl selenides with SO2Cl2 and, after recrystallization, hydrolysis/s
- Engman, Lars
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p. 1463 - 1466
(2007/10/02)
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- Phenylselenium Trichloride in Organic Synthesis. Reaction with Unsaturated Compounds. Preparation of Vinylic Chlorides via Selenoxide Elimination
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Phenylselenium trichloride, PhSeCl3, was reacted with a number olefinic compounds to produce (β-chloroalkyl)phenylselenium dichlorides.The addition was anti stereospecific and irreversible.The presence of an oxygen substituent (acyloxy or aryloxy group) in the allylic position of the olefin directed the attack of PhSeCl3 to occur regiospecifically anti-Markovnikov to give a (β-acyloxy/aryloxy-β'-chloroalkyl)phenylselenium dichloride.When the (β-chloroalkyl)phenylselenium dichlorides were treated in methylene chloride with aqueous sodium hydrogen carbonate, the selenium dichloride moiety was readily hydrolyzed to a selenoxide, which underwent the usual selenoxide elimination reaction to produce an allylic or a vinylic chloride.Symmetrical olefins containing no allylic hydrogens were converted to vinylic chlorides with retention of olefin geometry.Olefins containing a directing oxygen substituent in the allylic position afforded vinylic chlorides where the vinylic halogen atom was oriented 1,3 to the oxygen substituent (E/Z mixture).Other olefins afforded mixtures of allylic and vinylic halides in varying proportions.The reaction of phenyselenium tribromide, PhSeBr3, with some olefinic compounds was also investigated.This material showed the same stereo- and regiochemical behavior as PhSeCl3 in its addition reactions.However, the adducts were not useful for the preparation of vinylic or allylic bromides by using the hydrolytic selenoxide elimination reaction.
- Engman, Lars
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p. 4086 - 4094
(2007/10/02)
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- PREPARATION OF PYRIMIDINES AND PYRIDINES FROM ALKYL KETONES AND NITRILES IN PRESENCE OF PHOSPHORYL CHLORIDE
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The reaction of alkyl ketones with nitriles in the presence of POCl3 has been examined.It has been found that N-vinylimidoyl dichlorophosphates initially formed react further with excess nitriles or ketones to afford pyrimidine or pyridine derivatives, respectively.
- Zielinski, Wojciech
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p. 1639 - 1644
(2007/10/02)
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- Reaction of Phosphorus Pentachloride with 2-Acetylthiophene and Acetophenone
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The treatment of 2-acetylthiophene with PCl5, followed by dehydrochlorination, is known to be a poor method for synthesizing 2-ethynylthiophene (1a).Reinvestigation of the reaction showed the major products to be the E- and Z- isomers of 1,2-dichloro-1-(2-thienyl)ethylene (7a), with minor amounts of 1,1-dichloro-1-(2-thienyl)ethane (3a), 1-chloro-1-(2-thienyl)ethylene (4a), 2-(chloroacetyl)thiophene, and 2-(dichloroacetyl)thiophene.The treatment of acetophenone with PCl5 yielded similar products, and the mechanism of these reactions is discussed.The major product 7a could be converted into 1a by reaction with magnesium.The yield of 4a was increased when pyridine was also used, when only 1 equiv of PCl5 was added by portions to the ketone, or when catecholphosphorus trichloride was used instead of PCl5.The best method for converting 2-acetylthiophene into 1a goes through the enol phosphonate of 2-(bromoacetyl)thiophene, which is treated with sodium amide.
- Kagan, Jaques,Arora, Sudershan K.,Bryzgis, Marius,Dhawan, Som N.,Reid, Kevin,et al.
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p. 703 - 706
(2007/10/02)
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- Use of Kinetic Isotope Effects in Mechanism Studies. 4. Chlorine Isotope Effects Associated with Alkoxide-Promoted Dehydrochlorination Reactions
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The method of measuring k35/k37 for the alkoxide-promoted deprotiochlorination and dedeuteriochlorination reactions has been applied to C6H5CiH(CH3)CH2Cl (I-Cl), C6H5CiHClCH2Cl (V), and C6H5CiHClCF2Cl(III).For reactions occuring with ethanolic sodium ethoxide the following values for k35/k37 have been measured: I-Cl-h, 1.00590 + 0.00013, and I-Cl-d, 1.00507 +/- 0.00036 at 75 deg C; V-h, 1.00908 +/- 0.00008, and V-d, 1.00734 +/- 0.00012 at 24 deg C; III-h, 1.01229 +/- 0.00047, and III-d, 1.01003 +/- 0.00024 at 0 deg C.Methanolic sodium methoxide promoted eliminations gave similar results for V and III: V-h, 1.00978 +/- 0.00020, and V-d, 1.00776 +/- 0.00020 at 21 deg C; III-h, 1.01255 +/- 0.00048, and III-d, 1.01025 +/- 0.00043 at 20 deg C.The results for I-Cl are most consistent with an E2 mechanism, while the results for III and V suggest a multistep reaction sequence.The Arrhenius behavior of ethoxide-promoted dehydrochlorination of V-h gives a good linear correlation between -10 and 50 deg C, with an EaH = 21.26 +/- 0.05 kcal/mol and ln AH = 29.29 +/- 0.09.Rate constants measured for 55, 60, 65, and 70 deg C show increasing negative deviation from the slope.Similar behavior was not observed for V-d which resulted in EaD = 21.57 +/- 0.28 and ln AD = 28.37 +/- 0.28 when rate constants over a 50 deg C range (20 - 70 deg C) were used.The ΔEaD-H = 0.31 and AH/AD = 2.5 for an observed kH/kD = 4.24 at 25 deg C were similar for results obtained for III.The possibility that the high values of k35/k37 for both III and V could result from a chlorine isotope effect associated with the proton transfer step of an E1cB mechanism is discussed.
- Koch, Heinz F.,McLennan, Duncan J.,Koch, Judith G.,Tumas, William,Dobson, Brian,Koch, Nanci H.
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p. 1930 - 1937
(2007/10/02)
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- Vinylcations, 39. Zinc Chloride Catalysed Addition of Hydrogen Chloride to Cyclopropylalkynes
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Zinc chloride catalysed addition of hydrogen chloride to 1-cyclopropylalkynes 5a-e (R = CH3, c-C3H5, phenyl, p-tolyl, 4-methoxyphenyl) is studied and the results are compared with those of the addition of HCl/ZnCl2 to several substituted arylalkynes 10a-h.Thus, the alkynes are reacted with HCl/ZnCl2 in dichloromethane and the reaction products are investigated also with respect to their stereochemistry.All alkynes yield predominantly the direkt hydrogen chloride addition products.The 1-cyclopropylalkynes 5a-d give (E)-1-chloro-1-cyclopropyl-1-alkenes 15, and (E)-1-chloro-2-cyclopropyl-1-(4-methoxyphenyl)ethene (16e) is obtained as the major product from 5e (R = 4-CH3OC6H4).Moreover, ring opening to homoallenyl chlorides 19 and, as a side reaction, formation of the ketones 17 and 18 by the addition of water are observed.In a secondary addition reaction, the dichlorides 20 are also obtained by homoallyl rearrangement.The arylalkynes 10a-g react preferentially with formation of (E)-1-aryl-1-chloroalkenes 21.Relative rates are obtained by inter- and intramolecular competition reactions of the alkynes 23 and 5b-e with HCl/ZnCl2 showing the order of stabilization by substituents of the intermediate vinyl cation 2 to be 4-ClC6H4 E2 mechanism.The preferential formation of the addition products E-15, E-16, and E-21 is attributed to a syn-vinyl cation ion pair and to steric approach control of the β-substituents in the vinyl cation intermediate 2.
- Hanack, Michael,Weber, Erhard
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p. 777 - 797
(2007/10/02)
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- Reactions of Copper(I) Halide Complexes of Trivalent Phosphorus with Vinylic Halides
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The direct formation of the vinylic carbon to phosphorus bond has been accomplished via reaction of vinylic halides with copper(I) halide complexes of trialkyl phosphites.In addition, formation of varying amounts of vinylic chlorides may be observed if the reaction is performed by using vinylic bromides with copper(I) chloride complexes of trialkyl phosphites.This halogen-exchange reaction may be made synthetically useful through the employment of copper(I) chloride complexes of triaryl phosphites or phosphines.
- Axelrad, George,Laosooksathit, Surin,Engel, Robert
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p. 5200 - 5204
(2007/10/02)
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- Unsaturated Compounds containing Nitrogen. Part 4. Further Reactions of 1-Chloro-2,3-diazabutadienes with S-Nucleophiles
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1-Chloro-1,4-diaryl-2,3-diazabutadienes (Ar1CCl=NN=CHAr2), prepared by the reaction of thionyl chloride with aroylhydrazones (Ar1CONHN=CHAr2), react with thiosemicarbazide or thiocarbohydrazide to give 2-arylidenehydrazino-5-aryl-1,3,4-thiadiazoles, and with potassium thiocyanate to give 1-thiocyanato-1,4-diaryl-2,3-diazabutadienes which isomerize thermally to arylideneamino-5-aryl-1,3,4-thiadiazoles. 1-Chloro-1,4-diphenyl-2,3-diazabutadiene reacts with potassium ethylxanthate to give a 1-ethylxanthyl-2,3-diazabutadiene which on pyrolysis yields 2,5-diphenyl-1,3,4-thiadiazole.
- Flowers, William T.,Robinson, John F.,Taylor, David R.,Tipping, Anthony E.
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p. 349 - 355
(2007/10/02)
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- Kinetics and Stereochemistry of the Addition of Chlorine to Styrenes
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The chlorination of several ring- and side-chain-substituted styrenes has been studied in anhydrous acetic acid, in both the presence and absence of added perchlorate, chloride, and acetate salts.The reactions give three types of product: the 1,2-dichlorides arising from simple addition, 1-acetoxy-2-chloro compounds from addition followed by solvent incorporation, and β-chlorostyrenes from an addition-elimination process.The reactions are completely regiospecific in the Markownikoff sense, and the addition-elimination products are formed with high stereoselectivity.However, both types of addition product are formed nonstereospecifically.Both the product distribution and stereoselectivity are remarkably insensitive to added perchlorate, chloride, or acetate, and very high concentrations of these salts (ca. 1.0 M) are required to produce any significant change in product composition.These results are explicable in terms of a product-determining intermediate which consists of an intimate ion pair between an open β-chlorobenzyl carbonium ion and a tightly held chloride counterion.However, since (E)- and (Z)-1-phenylpropenes do not give similar product distributions under any conditions used, rotation of the Cα-Cβ bond in the carbonium ion must be highly restricted.The rates of reaction have been studied by a combination of potentiometric and stopped-flow spectrophotometric techiques.The reactions are first order in chlorine and first order in olefin and are generally very fast, with most of the rate constants being in the range 102-105 L mol-1 s-1.The rate constants for the ring-substituted styrenes give a good linear correlation against ?+ with a β value of -3.22.This value is less negative than expected from a comparison with other electrophilic additions and is discussed in terms of an earlier transition state with less charge development at Cα than in the analogous bromination reaction.The activation parameters obtained for two of the styrenes support this hypothesis.There is no direct evidence for chlorine bridging at either the transition state or the intermediate stage.
- Yates, Keith,Leung, Hei Wun
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p. 1401 - 1406
(2007/10/02)
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