- One-pot synthesis of α-bromoacetals of ketones from secondary alcohols and 1,3-dibromo-5,5-dimethylhydantoin (DBDMH) in ethylene glycol
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α-Bromoacetals of ketones were prepared from various secondary alcohols with 1,3-dibromo-5,5-dimethylhydantoin (DBDMH) and ethylene glycol through oxidation, bromination, and acetalization in one pot without the use of other catalysts under mild conditions. The effects of DBDMH, the solvent, and N-bromosuccinimide on the reaction were investigated. Under the optimal conditions, most α-bromoacetals of ketones were obtain in 90–98% yields.
- Han, Bingbing,Zheng, Zubiao,Wu, Fang,Wang, Aidong
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- A Convenient Procedure for the Synthesis of Acetals from α-Halo Ketones
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A study for determining the scope and limitations of a procedure for synthesising ethylene acetals from haloketones is presented. The method uses 1,2-bis(trimethylsilyloxy)ethane, BTSE, as reagent and Nafion-TMS as catalyst. Two procedures have been tested: (A) stoichiometric amounts of the haloketone and BTSE and a catalytic amount of Nafion-TMS were heated to reflux in chloro-form solution, and (B) stoichiometric amounts of the reactants and a catalytic amount of Nafion-TMS were heated to 90-100°C in the absence of solvent. The following ketones have been tested: 2-bromo-1-phenyl-1-ethanone, 2-bromo-cyclopentenone, 3-bromo-3-methyl-2-butanone, 3-chloro-3-methyl-2-butanone, 1-bromo-3,3-dimethyl-2-butanone, 1-chloro-3,3-dimethyl-2-butanone, 2-bromocyclohexanone, 2-chloro-1-cyclohexyl-1-ethanone, 1,1-dibromo-3,3-dimethyl-2-butanone, 1,3-dibromo-3-methyl-2-butanone, 1,3-dibromo-2-butanone, 1,3-dibromo-2-propanone, 2-chloro-1-phenyl-1-ethanone, and endo-2-bromocamphor. Yields were in the range 57-100% with the exceptions of endo-2-bromocamphor which afforded 10% yield and the dibromoketones 1,1-dibromo-3,3-dimethyl-2-butanone and 1,3-dibromo-3-methyl-2-butanone for which the method failed. Factors determining the scope and limitations are briefly discussed. Full experimental details and spectroscopic data of the acetals are given.
- Carlson, Rolf,Gautun, Hanna,Westerlund, Andreas
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- Application of poly(vinylphenyltrimethylammonium tribromide) resin as an efficient polymeric brominating agent in the α-bromination and α-bromoacetalization of acetophenones
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The applications of a new supported tribromide reagent based on poly(vinylbenzyltrimethylammonium hydroxide) resin (Amberlite 717) were reported. This supported tribromide resin was used directly in α-bromination and α-bromoacetalization of acetophenones without any other catalyst under mild conditions. The effects of solvents and the amount of the supported tribromide resin on the reactions were investigated. Under the optimal conditions, most of α-bromo and α-bromoacetal of acetophenones were selectively obtained in excellent yields.
- Han, Bingbing,Zheng, Zubiao,Zheng, Dongcheng,Zhang, Lei,Cui, Peng,Shi, Jianjun,Li, Changjiang
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supporting information
p. 2512 - 2520
(2019/07/04)
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- One-step for the preparation of α-haloacetal of ketones with N-bromosuccinimide/N-chlorosuccinimide (NBS/NCS) and ethylene glycol
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A new process that could directly prepare α-haloacetal of ketones from various ketones with N-halosuccinimide (NBS/NCS) and ethylene glycol in one step without any other catalysts was reported. The effects of solvents, NBS/NCS and reaction temperature were investigated. Under the optimal condition, most of α-haloacetals of ketones were obtained in 90–100% yield.
- Zheng, Zubiao,Han, Bingbing,Wu, Fang,Shi, Tengfei,Liu, Jie,Zhang, Yong,Hao, Jialong
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p. 7738 - 7743
(2016/11/17)
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- Sc(OTf)3-Catalyzed Addition of Bromomagnesium 2-Vinyloxy Ethoxide to Various Aldehydes Leading to Protected Aldol Products
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The addition of bromomagnesium 2-vinyloxy ethoxide to various aldehydes in the presence of 10 mol% Sc(OTf)3 provides a broad range of functionalized protected aldol compounds. The enantioselective preparation of these aldols can be achieved via a Swern oxidation-CBS reduction sequence. Use of the dioxolane derived from 2-bromocyclohexanone provides the expected aldol product as the anti diastereoisomer (dr >99:1).
- Quinio, Pauline,Kohout, Laura,Roman, Daniela Sustac,Gaar, Jakob,Karaghiosoff, Konstantin,Knochel, Paul
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p. 1715 - 1719
(2016/07/06)
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- An Enantioselective Approach to 4-O-Protected-2-cyclopentene-l,4-diol Derivatives via a Rhodium-Catalyzed Redox-Isomerization Reaction
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Kinetic resolution of a series of cyclopentene-1,4-diol derivatives has been successfully achieved with enantiomeric excess up to 99.4% and a kf/ks ratio of 55 by a rhodium-catalyzed redox-isomerization reaction in a noncoordinating solvent.
- Ren, Kai,Zhao, Mengmeng,Hu, Bei,Lu, Bin,Xie, Xiaomin,Ratovelomanana-Vidal, Virginie,Zhang, Zhaoguo
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p. 12572 - 12579
(2016/01/09)
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- Optimization of Grignard ring-opening of α-brominated dioxolanes for the preparation of β-hydroxy-protected vinyl ethers by a three-step one-pot procedure
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Aliphatic, cyclic, and aromatic benzoate-protected γ-hydroxy enol ethers were prepared from α-brominated dioxolanes by a three-step reaction procedure and a one-pot protocol involving Grignard reagent formation, ring-opening, and final benzoate protection
- André, Mathieu,Letribot, Boris,Bayle, Martine,Mounetou, Emmanuelle,Chezal, Jean-Michel
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p. 6107 - 6110
(2012/11/07)
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- Synthesis and application of poly(diallyldimethylammonium tribromide) as a novel polymeric brominating agent
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In this study, the synthesis and applications of a new supported tribromide reagent based on poly(diallyldimethylammonium chloride) is reported. This supported tribromide is used in α-bromoacetalization of ketones, bromination of alkenes and regioselective bromination of activated aromatic compounds. This method is mild and no Br2 and HBr were used. Other advantages of this reagent are stability, high efficiency, simple filtera- bility and reusability. In this study, the synthesis and applications of a new supported tribromide reagent based on poly(diallyldimethylammonium chloride) is reported. This supported tribromide is used in α-bromoacetalization of ketones, bromination of alkenes and regioselective bromination of activated aromatic compounds. This method is mild and no Br2 and HBr were used. Other advantages of this reagent are stability, high efficiency, simple filterability and reusability. Copyright
- Hossein, Mahdavi,Zahra, Kachoei
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experimental part
p. 2221 - 2225
(2011/10/12)
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- A New α-Iodination of Ketones Using Iodine-Ammonium Cerium(IV) Nitrate in Alcohol or Acetic Acid
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The direct α-iodination of various ketones using iodine-ammonium cerium(IV) nitrate in acetic acid or alcohol gave the corresponding α-iodo ketones in high yields. The effect of cerium salt on the iodination of ketones, and the iodination of 5α-cholestan-3-one using several methods are also discussed. In the reaction of 3,3,5-trimethylcyclohexanone and unsymmetrical ketones, such as 2-hexanone and 2-heptanone, using methanol, ethanol, 1-propanol, and 2-propanol, the regioselective iodination product was obtained. In the case of bromination, the reaction of ketones with bromine and ammonium cerium(IV) nitrate also yielded the corresponding α-bromo ketones.
- Horiuchi, C. Akira,Kiji, Shinji
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p. 421 - 426
(2007/10/03)
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- The Conformational Behaviour of 10-Substituted Spirodecanes
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The conformational behaviour of 10-X-substituted 1,4-dioxa- and 1,4,6-trioxaspirodecanes 1-4 has been studied by 13C-, 19F- and 1H-NMR spectroscopy.Two X-ray analyses of (2a,e) are presented, and their implications to cleavage reactions of chiral acetals are discussed.Participation of twist boat forms in the conformeric equilibrium of at least 1c has been made plausible by observing 13C, 19F-NMR coupling constants.The ratios of axial to equatorial conformers in 1-4 have been calculated by molecular mechanics.
- Wolff, J. Jens,Frenking, Gernot,Harms, Klaus
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p. 551 - 561
(2007/10/02)
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- The Octant Rule. 15. Antioctant Effects: Synthesis and Circular Dichroism of 2-exo- and 2-endo-Alkylbicycloheptan-7-ones and -bicyclooctan-8-ones
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Circular dichroism spectra of the n -> ?* transition of alkylbicycloheptan-7-ones and alkylbicyclooctan-8-ones have helped to define the boundary separating front and back octants in the ketone octant rule.Series of (1S,4R)-exo-2(R)-alkylbicycloheptan-7-ones and (1S,4R)-endo-2(S)-alkylbicycloheptan-7-ones were prepared and their circular dichroism (CD) spectra measured and compared with (1S,3R)-4(S)(a)- and -4(R)(e)-methyladamantan-2-ones.The alkyl groups include methyl, ethyl, and n-hexyl.Similarly, (1R,5S)-exo-6(R)- and -endo-6(S)-methylbicyclooctan-8-ones were synthesized and their CD spectra determined.The CD Cotton effects for the n -> ?* transitions of these ketones aid in defining the third nodal surface of the octant rule as convex, bending outward from behind the carbonyl carbon toward oxygen.The ring skeletal symmetry was examined by molecular mechanics (MM2) calculations, which located the coordinates (positions) of lone dissymetric methyl groups relative to the carbonyl group. 13C NMR spectroscopy confirmed the methyl group locations and provided additional new examples of the γ-gauche effect.
- Lightner, David A.,Crist, B. Vincent,Kalyanam, Nagabushanam,May, Leslie M.,Jackman, Dennis E.
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p. 3867 - 3878
(2007/10/02)
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- UNE NOUVELLE METHODE DE BROMATION : LE TRIBROMURE DE TETRABUTYLAMMONIUM.
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Tetrabutylammonium tribromide (TBA Br3) is used under mild conditions as bromating agent for the addition on double bonds of alkenes and for selective α-substitution of acetals in high yields.
- Fournier, M.,Fournier, F.,Berthelot, J.
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p. 157 - 158
(2007/10/02)
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- STEREOCHEMICAL STUDIES-XXVI CONFORMATIONAL EQUILIBRIA OF KETALS OF 2-SUBSTITUTED CYCLOHEXANONES
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The positions of the conformational equilibria in a series of 2-substituted cyclohexanone ketals have been determined by 1H NMR.For the ethylene ketals 6 the equatorial conformer has been found to be enthalpically preferred.The other ketal syst
- Mursakulov, Ismail G.,Guseinov, M. M.,Kasumov, N. K.,Zefirov, Nikolai S.,Samoshin, V. V.,Chalenko, E. G.
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p. 2213 - 2220
(2007/10/02)
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