- 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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- 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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- 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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- 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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- 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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- An approach to the synthesis of unsymmetrically substituted chlorobiphenyls
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The Diels-Alder cycloaddition of o-chloranil with phenylacetylenes substituted with chlorine in the ring can afford chlorobiphenyls upon photodecomposition of the brodged diketone adduct.Biphenyls derived from 3-chloro-, 4-chloro-, 2,4-dichloro-, and (2,5
- Pyle, James L.,Shaffer, Alan A.,Cantrell, Joseph S.
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p. 115 - 118
(2007/10/02)
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